Physics Questions & Problems

for the Research Text

Second Semester

Chapters 10-25

Here are the Answers to the Problems.

The problems listed are the ones that we must do in our portfolios.

Here are the Assignment Numbers.

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Assignment 27 Page 232

Questions GROUP A

1. In what ways may energy be transferred?

2. Distinguish between mechanical waves and electromagnetic waves.

3. What are three requirements for the production of mechanical waves?

4. (a) What is a disturbance? (b) What constitutes the disturbance when a wave moves across the surface of a pond? (c) What constitutes the disturbance when a longitudinal wave travels through the air?

5. How does an elastic material behave as a wave medium?

6. (a) Distinguish between transverse and longitudinal waves. (b) Give an example of each.

7. Define (a) pulse; (b) crest; (c) trough; (d) compression; (e) rarefaction.

8. For wave motion, define (a) speed; (b) phase; (c) frequency; (d) period; (e) wavelength; (f) amplitude.

9. What does a wave source supply to the medium through which the wave passes?

10. A pebble is dropped into a pond of water. Neglecting losses, how does the resulting wave disturbance vary with the distance from the source?

11. Neglecting damping losses, would you expect the amplitude of an advancing surface wave on a pond to diminish with distance from its point source at the same rate as an advancing sound wave diminishes with distance from its point source in ait? Justify your conclusion qualitativley.

12. A charge of dynamite is exploded at a construction site overlooking a lake. (a) A grass fire is ignited nearby (b) A window in a cottage nearby is shattered. (c) A flock of birds fly frantically out of the trees in the surrounding area. (d) A smoke rises from the site of the explosion (e) A huge boulder falls into causing (f) a small sailboat that is passing nearby to capsize. Identify the energy-transport mechanism sponsible for each event.

Problems GROUP A

Hint for following problems: v = fl

1. What is the speed of a periodic wave disturbance, frequency 2.5 hz and wavelength 0.60 m?

2. Calculate the wavelength of water waves that have frequency of 0.50 hz and speed 4.0 m/s.

3. The speed of transverse waves in a string string is 15 m/s. If a source produces a disturbance, frequency 5.0 hz, what is the wavelength of the wave produced?

4. A periodic transverse wave, frequency 10.0 hz, travels along a string. The distance between a crest and either adjacent trough is 1.50 m. What is (a) the wavelength, (b) the speed of the of wave?

5. A periodic longitudinal wave, frequency 20.0 hz, travels along a coil spring. If the distance between successive compressions is 0.40 m, calculate speed of the wave.

6. What is the wavelength of a periodic longitudinal wave in a coil spring, frequency 8.0 hz and speed 20 m/s?

7. A wave generator produces 16 pulses in 4.0 seconds. (a) What is its period? (b) What is its frequency? Hint: P = 1 / f , f = 1 / P.

8. One pulse is generated every 0.10 s in a tank of water, and the wavelength of the surface wave measures 3.3 cm. What is the propagation speed?

Assignment 28 Page 249

Questions GROUP B

1. How does a pulse on a taut string differ from the incident pulse after being reflected at a fixed termination?

2. List the common properties of waves give an illustration of each.

3. Make a drawing showing two transwaves of the same wavelength of different amplitudes that are in phase. Graphically find the wave pattern that results if these two waves are superposed.

4. Repeat Question 3 with waves of the same amplitude but with one having twice the wave length of the other. At t = 0, the displacement of both waves is zero. At t = T/4 later for each, the displacement is maximum positive.

5. Repeat Question 4, but take the displacement as zero for the wave of longer wavelength and as positive maximum for the wave of shorter wavelength at t = O while the reverse applies at t = T/4.

6. In your drawings of Questions 4 and 5 mark the points of maximum displacement and zero displacement. Do they occur at the same points at t = O as at t = T/4? Would you consider the resulting pattern as a standing wave or a progressing wave?

7. What are the requirements for production of a standing wave pattern?

8. What are loops and nodes in a standing wave pattern?

9. When two waves interfere, what influence does each exert on the progress of the other? Explain.

10. When two waves interfere, is there a loss of energy in the system? Explain.

11. Distinguish between the effects of a fixed termination and a free termination of a wave-transmission medium.

12. Two rooms are separated by a special soundproof partition except for a connecting doorway. How can you explain the fact that a sound produced anywhere in one room can be heard anywhere in the other?

13. A new phenomenon has been observed in which there is a transfer of energy. What type of experiments would you propose to determine whether it is a particle or wave phenomenon?

14. What is an impedance transformer?

15. A wave disturbance travels through a uniform medium to its termination, where a small part of the wave enrgy is transferred to the terminating medium and the remainder is reflected. How would you describe impedance of the terminating medium relative to the impedance transmitting medium?

16. Suggest two possible ways of modifying the wave-transfer system described in Question 15 to the reflection of wave energy.

Problems GROUP B

Hint for following problems: v = fl

1. Electromagnetic waves travel through space at a speed of 3.0 x 108 m/s. The visible region of the spectrum has wavelengths ranging from about 4.0 x 10-7 m in the violet region to about 7.6 x 10-7 m in the red region. What is the frequency range of visible light?

2. A string stretched between two clamps is 2.0 m long. When plucked at the center, a standing wave is produced that has nodes at the clamped ends and a single loop at the center. By means of a stroboscope, the string is observed to complete 7.0 vibrations per second. (a) What is the wavelength of the component traveling waves? (b) What is the speed of the transverse waves in the string?

3. Periodic longitudinal waves are generated in a coil spring from a vibrating source at one end of the spring as; shown in Figure 10-8.

The of the vibrating source is 15.0 hz. The distance between successive compressions is 41.0 cm. What is the speed of each compression moving along spring?

4. An observer determined that 2.5 m separated a trough and an an adjacent crest of surface waves on a lake and counted 33 crests passing in 30 s. What was the speed of these waves?

5. Two physics students were fishing from a boat anchored in a lake 24 m from shore. One student observed that the boat rocked through 11 complete oscillations in 19 s and that one crest passed the boat with each oscillation. The other student noted that each crest required 6.5 s to reach shore. (a) What was the period of: the surface wave? (b) What was wavelength? Hint: P = 1 / f , f = 1 / P.

Assignment 29 Page 264

Questions GROUP A

1. How are sounds produced?

2. Why is sound not transmitted through a vacuum?

3. (a) State the speed of sound in air at OoC in metric units of measure. (b) What is the rate of increase of speed with rise in temperature?

4. Distinguish between intensity loudness .

5. Distinguish between frequency pitch.

6. The engineer of a diesel locomotive sounds the horn as the train approaches you. How does the pitch you hear compare with the pitch the engineer hears? Hint: The Doppler Effect.

7. How do the vibrations of the source of a musical tone differ from the vibrations of the source of a noise?

8. (a) What is the range of audio frequencies? (b) What name is applied to sound vibrations below the audio range? (c) What name is applied to sound vibrations above the audio range?

9. Referring to Figure 11-6,

interpret (a) the threshold of hearing curve and (b) the threshold of pain. curve. At a sound frequency of 1000 hz, what is (c) the intensity of the threshold of hearing, (d) the relative intensity of the threshold of hearing, (e) the intensity of the threshold of pain, and (f) the relative intensity of the threshold of pain?

Questions GROUP B

10. Describe how a vibrating reed sets up longitudinal waves in the air surrounding it and thereby transfers its energy to the surrounding air.

11. (a) How does variation in the work done in setting a reed in vibration affect the sound produced? (b) How does variation in the length of the vibrating portion of the reed affect the sound?

12. Explain why the audibility of a sound disturbance in an enclosed gaseous medium diminishes as the density of the gas is lowered.

13. Why is the relative intensity of sound measured on a logarithmic scale?

14. What condition determines the upper limit of the sonic spectrum in a given transmitting medium?

15. Explain the meaning of the statement, "the relative intensity of sound in the room is 40 db."

16. Sound intensity, I, is a measured quantity having dimensions of power per unit area, P/A, expressed in watts/centimeter2. The relative intensity of sound, b , is also a measured quantity expressed in decibels, the decibel, db, being a dimensionless unit. Explain the dimensionless character of the decibel. Hint: Ratios have no units (they cancelled out).

Problems GROUP A

Hints: d = vt, (dist = velocity x time), v = 331 m/s + [(0.6)temp], 1 km = 1000 m.

1. What time is required for sound to travel 5.00 km if the temperature of the air is 10.0 oC?

2. What is the wavelength, in meters, of the sound produced by a tuning fork that has a frequency of 320.0 hz? The temperature of the air is 15 oC.

3. The echo of a ship's foghorn, reflected from an iceberg, is heard 5.0 s after the horn is sounded. The temperature is -10.0 oC. How many meters away is the iceberg? Hint: The sound makes a round trip over and back.

4. A rifle is fired in a valley with parallel vertical walls. The echo from one wall is heard in 2.0 s; the echo from the other wall 2.0 s later. The temperature is 20 oC. What is the width of the valley?

Assignment 30 Page 277

Questions GROUP A

1. (a) Why does a tuning fork sound louder when its stem is pressed against a table top? (b) Why doesn't its sound last as long?

2. What conditions are necessary to produce resonance?

3. To produce the best resonance, how must the length of a closed tube compare with the wavelength of the sound?

4. To produce the best resonance, how must the length of an open tube compare with the wavelength of the sound?

5. How do the frequencies of notes an octave apart compare?

6. (a) What is a fundamental? (b) How does a string vibrate to produce the fundamental?

7. Which iaw of strings is used (a) in tuning a guitar; (b) in playing the instrument?

8. Given two sound wave trains of the same frequency traversing the same medium simultaneously, describe the conditions for (a) constructive interference; (b) destructive interference. (c) What changes and/or additions in the above wave specifications are required for the interfering wave trains to produce a beat note?

Questions GROUP B

9. Why is it easy to distinguish between the sound produced by a piano and a trombone even if both play the same note?

10. How do the strings on a piano illustrate the laws of strings?

11. Suggest a function of the bridge between the strings and the sounding board of a musical instrument such as a cello.

12. Suppose a piano tuner has tuned the notes middle C and G to frequencies of 262 hz and 392 hz respectively. The note G is then beat against low C, which is one octave below middle C. What should be heard to indicate that low C has been adjusted to its proper frequency?

13. Given two tuning forks that the same frequency, suggest a way to hear beats between them.

Problems GROUP A

Hints: Quarter wave resonator l = 4(l + 0.4d), Half wave resonator l = 2(l + 0.8d), v = 331 m/s + [(0.6)temp], Beats = f2 - f1.

1. What is the frequency of a tuning fork that resonates with an open tube 25.0 cm long and 2.0 cm in diameter when the temperature is 20.0 oC?

2. A tuning fork, frequency 384 hz, produces resonance with a closed tube 20.0 cm long and 4.0 cm in diameter. What is the speed of sound?

3. A tuning fork has a frequency of 440 hz. If another fork of slightly lower pitch is sounded at the same time, the beats produced are 5/s. What is the frequency of the second tuning fork?

4. How many beats will be heard each second when a string, frequency 288 hz, is plucked simultaneously with another string, frequency 296 hz?

5. A violin string is 25.4 cm long and produces a fundamental frequency of 440 hz. What change in length is required to produce a frequency of 523.3 hz?

6. Compare the frequency of one string 25 cm long and 0.50 mm in diameter with that of another 100 cm long and 0.25 mm in diameter, assuming all other factors are constant.

7. Two tuning forks of 320 hz and 324 hz are sounded simultaneously. What sound will the listener hear?

8. A violin string is 26.7 cm long and has a resonant frequency of 327.6 hz. What change in length is required to lower the resonant frequency to 293.7 hz?

Problems GROUP B

Hint: Be sure to change cm into meters. 1 m = 100 cm, so 1 cm = 0.01 m.

13. An organ pipe open at both 1.23 m long and has a diameter 10 cm. (a) What is its frequency when the air temperature 15 oC? (b) What are the the two lowest harmonics along with the fundamental.

14. An organ pipe closed at one end 0.76 m long and has a diameter 5.0 cm. The air temperature is 12 oC (a) Determine its fundamental frequency. (b) What are the frequencies of the two lowest harmonics produced along with this fundamental tone?

Assignment 31 Page 301

Questions GROUP A

1. What is the modem view of the nature of light?

2. Arrange the following in order of their increasing wavelength: visible light, infrared radiations, ultraviolet radiations, X rays, radio waves, gamma rays.

3. Compare visible light and sound as to: (a) origin, (b) transmitting media, (c) wavelength, (d) type of wave, (e) speed.

4. How does an atom of a substance radiate energy according to the quantum theory?

5. The flatiron is a source of radiations that cannot be detected by the eye. (a) Would you expect an ordinary photoelectric cell to detect these radiations? Explain. (b) Suggest a way to prove that such radiations are emitted.

Questions GROUP B

6. A beam of light passes through a small aperture and illuminates the blackened bulb of a thermometer. A piece of ordinary glass is placed over the aperture and the thermometer reading drops two degrees. The glass is replaced by a quartz window and the thermometer reading returns approximately to the original value. What do the results suggest concerning the nature of the light source? Explain.

7. (a) State the three laws of photoelectric emission.

(b) To what extent is a wave model of light successful in explaining these laws?

8. Given a monochromatic (single frequency) light source to illuminate a photocell, how can you explain fact that photoelectrons are ejected at various velocities ranging up to a maximum value?

9. How does the pair of curves in Figure 12-11 show that the velocity of photoelectrons is independent the intensity of the light the photocell?

10. What special significance can you attach to the photoelectric situation in which the photon energy hf transferred to an electron is just equal the work function w of the emitter?

11. (a) Distinguish between coherent incoherent light waves. (b) describe the light emitted by a laser.

12. How would you defend the assertion that the production of X rays illustrates the inverse photoelectric effect?

No Problems in this assignment.

Assignment 32 Page 313

Questions GROUP A

1. Distinguish between luminous and illiuminated objects.

2. Define and illustrate the following: (a) transparent, (b) translucent, opaque.

3. What are the physical quantities generally measured in practical photometry?

4. Define luminous flux.

5. Which of the quantities from Question 3 is measured in fundamentai units? (b) Which are measured in derived units?

6.What is our chief method of providing artificial light?

Problems GROUP A

Note: . Assume filament lamps to be point sources.

1. The distance from the earth to the sun is approximately 1.5 x 108 km. What time, in minutes, is required for light from the sun to reach the earth? Hint: d = vt. Speed of light is 3.0 x 105 km/s, 1 min = 60 sec.

2. What is the illumination on the page of a book 1.20 m directly below a source whose intensity is 125 cd? Hint: E = I/d2.

3. It is recommended that the illumination be 540 lm/m2 for newspaper reading. How far from the paper should a 265-cd source be placed to provide this illumination? (Assume the paper to be perpendicular to the luminous flux reaching it.)

4. What is the maximum illumination 1.50 m from a lamp whose intensity is 150 cd?

5. The amount of illumination thrown on a screen by two sources of light is the same when the distances from the lamps to the screen are 3.0 m and 2.0 m, respectively. If the intensity of the first lamp is 20 cd, what is the intensity of the second lamp?

6. A lamp, intensity 16.0 cd, is placed at the O.O cm mark on a meter stick. A lamp of unknown intensity is placed at the 100.0 cm mark. If a Bunsen photometer is equally illuminated at the 60.0-cm mark, what is the intensity of the unknown lamp?

7. A photometer is in balance on a meter stick when a 40.0 cd lamp and a second lamp are 100.0 cm apart, and the grease spot is 30.0 cm from the second lamp. Find the intensity of this lamp.

Assignment 33 Page 329

Questions GROUP A

1. What three factors determine theamount of light an object will reflect?

2. What are the two laws of reflection?

3. When you look in a plane mirror, do see yourself as others see you? Explain.

4. Illustrate the following by diagram as they are related to curved mirrors: Center of curvature, vertex, principal axis.

5. What type of mirror produces real images?

6. In what ways can spherical aberration in mirrors be reduced?

Questions GROUP B

7. Suppose we write the word "light" on a mirror with white paint. When the mirror is placed in a beam of sun-light, the reflection of the sunlight on a smooth wall consists of a bright area in which the letters of the word "light" appear dark. Explain.

8. What kind of trick mirror produces (a) a short, fattened image; (b) a tall, thin image?

9. What kinds of mirrors could be used and where should the object be placed to produce (a) an enlarged real image, (b) a reduced real image, (c) a real image the same size as the object, (d) an enlarged virtual image, (e) a reduced virtual image?

10. (a) Construct a ray diagram to show the formation of an image by a concave mirror when the object is at a finite distance beyond the center curvature. (b) Describe fully the image that is formed.

11. (a) Construct a ray diagram to the formation of an image by a cave mirror when the object is tween the principal focus and the center of curvature. (b) Describe image formed.

12. (a) Construct a ray diagram to the formation of an image by a convex mirror. (b) Describe fully the image that is formed.

Problems GROUP A

1. A concave mirror has a focal length of 10.0 cm. What is its radius of curvature?

2. If the radius of curvature of a curved mirror is 8 cm, what is its focal length?

3. While you are looking at the image of your feet in a plane vertical mirror, you see a scratch in the glass. Assuming your height to be 1.76 m, what is the approximate height of the scratch from the floor?

4. The light from a distant star is collected by a concave mirror. If the radius of curvature of the mirror is 150 cm, how far from the mirror is the image?

5. An object is placed 25.0 cm from a concave mirror whose focal length is 5.00 cm. Where is the image located?

6. An object 25.4 cm high is located 91.5 cm from a concave mirror, focal length 15.0 cm. (a) Where is the image located? (b) How highs it?

7. An object placed 50.0 cm from a spherical concave mirror gives a real image 33.3 cm from the mirror. (a) What is the radius of curvature of the mirror? (b) If the image is 30.5 cm high, what is the height of the object?

8. An object and its image in a mirror are the same height when object is 36.4 cm from the mirror. What is the focal length of the mirror?

14. A physics student 1.80 m tall stands in front of a mirror admiring the reflected image. Assume the student's eyes are 10 cm below the top of the head. (a) What is the smallest vertical mirror that will enable the entire image to be seen? (b) Is the length of the mirror dependent upon the distance between the student and the mirror? (c) Construct a ray diagram that supports your answers.

Assignment 34 Page 340

Questions GROUP A

1. Define (a) refraction, (b) angle of refraction, and (c) index of refraction.

2. What property of a transparent substance causes the refraction of light rays that strike it at an oblique angle?

3. What are the three laws of refraction?

4. What is meant by the terms (a) critical angle and (b) total reflection?

5. What practical use is made of the index of refraction of a substance?

Questions GROUP B

6. You are looking diagonally down at a fish in a pond. To the fish, assuming that it can see you, does your head appear higher or lower than it actually is?

7. Explain why we see the sun before it actually rises above the horizon in morning, and why we see it has dropped below the horizon in the evening.

8. Which is the better reflector of light, a right-angle prism or a plane, silvered mirror? Explain.

9. Why are totally reflecting prisms usually designed so that light enters and leaves the prism at an angle 90o respect to the surface?

10. Why is a diamond more brilliant than a glass imitation cut the same way?

Problems GROUP A

Hints: Index of refraction in medium = speed of light in vacuum / speed of light in medium. And n = sin i / sin r where n = index of refraction, i = angle of incidence, and r = angle of refraction.

Speed of light in vacuum is 300,000 km/s, 3 x 105 km/s.

1. The speed of light in chloroform is 1.99 x 108 m/s. What is its refractive index?

2. What is the speed of light in kilometers per second in a diamond that has a refractive index of 2.42?

3. A penny at the bottom of a glass cylinder is 30.0 cm below the eye. If water is poured into the cylinder to a depth of 16.0 cm, how much closer does the coin appear? Hint: use the ratios of indexes of refraction that make it shallower.

4. A light ray passes from air into the surface of a Lucite block at an angle with the Lucite surface of 48.5o. What is the angle of refraction? (Index of refraction values are listed in Appendix B, Table 18:

Problems GROUP B

5. A ray of light passes from a medium of refractive index 1.33 into a medium of refractive index 1.50. The angle incidence is 45.0o. (a) By the construction tion method, determine the angle refraction. (b) Compute the angle refraction.

6. The angles of incidence and refraction of a ray of light passing from air int6 water are 60.0o and 41.0o. Find index of refraction of the water.

7. Find the critical angle for carbon-tetrachloride-to-air surface.

8. A physics student wished to know whether a glass cube to be used in an experiment was composed of flint glass. A light ray passing form air into the cube was traced and the angles of incidence and refraction determined to be 35.0o and 20.9o respectively. (a) What index of refraction did these data yield? (b) What glass did the student have? See Appendix B, Table 18 above.

Assignment 35 Page 353

Questions GROUP A

1. (a) What causes spherical aberration in lenses? (b) How can it be remedied?

2. Of which case of converging lenses is the simple magnifier an application?

3, Explain the lens system and image formation of a compound microscope in terms of the lens cases used.

4. Explain the lens system and image formation of a refracting astronomical telescope in terms of the lens cases used.

5. How does a terrestrial telescope compare with a refracting astronomical telescope?

Questions GROUP B

6. What kind of lenses could be used and where should the object be placed to produce (a) an enlarged real image, (b) a reduced real image, (c) a real image the same size as the

7. When the distance between a projector and the screen is increased, what adjustment must be made in the distance between the film and the objective lens to bring the image back into focus?

8. Is the focal length of a crown-glass diverging lens changed when the lens is immersed in water? Justify your answer.

9. A double convex lens in air acts as a converging lens. (a) Can it act as a diverging lens in another medium? (b) Construct a ray diagram to illustrate your response to (a).

10. Suppose you were going to use a clear plastic bag inflated with air as an underwater converging lens. (a) What shape should the inflated bag have? (b) Illustrate your response to (a) with an appropriate ray diagram.

Problems GROUP A

Hint: Use the lens and size formulae.

1. A converging lens has a focal length of 20.0 cm. If it is placed 50.0 cm from an object, at what distance from the lens will the image be?

2. If an object is 10 cm from a converging lens of 5 cm focal length, how far from the lens will the image be formed?

3. The focal length of the lens in a box camera is 10.0 cm. The fixed distance between the lens and the film is 11.0 cm. If an object is to be clearly focused on the film, how far must it be from the lens?

4. An object 3.0 cm tall is placed 20 cm from a converging lens. A real image is formed 10 cm from the lens. What is (a) the focal length of the lens, (b) the size of the image?

5. An object 30 cm from a converging lens forms a real image 60 cm from the lens. (a) Find the focal length of the lens. (b) What is the size of the image if the object is 5 cm high?

9. What is the magnifying power of a simple magnifier whose focal length is 10 cm?

Problems GROUP B

15. The tube of a microscope is 160 mm long. If the focal length of the eyepiece is 30.0 mm and the focal length of the objective is 5.00 mm, find the magnifying power.

Assignment 36 Page 360

Questions GROUP A

1. Why does a prism disperse sunlight into a band of colors?

2. What property of light determines its color?

3. What name is given to electromagnetic radiations having wavelengths slightly (a) longer and (b) shorter than visible light?

4. If a black object absorbs all light rays incident upon it, how can it be seen?

5. What is the appearance of a red dress in a closedroom illuminated only by green light? Explain.

6. (a) What are the primary colors of light? (b) Define a complementary color. (c) Name the complement of each primary color.

7. Why can't white paint be made orange paint by addrng a pigment of another color?

8. How could you demonstrate that piece of white-hot iron gives off light?

9. The focal length of a converging is determined experimentally using red light. (a) How will this focal length compare with that for light? (b) Construct a ray diagram to support your conclusion in (a).

10. Suppose a diverging lens is substituted for the converging lens in Question 9. (a) How will the focal length of the lens for red light compare with that for green light? (b) Construct an appropriate diagram to support your conclusion.

No Problems this time.

Assignment 37 Page 371

Questions GROUP A

1. How do the colors of a soap bubble originate?

2. Why are the various colors of white light separated by a diffraction grating?

3. Will the angular separation between red and blue rays be greater in the first-order or second-order spectrum of white light produced by a diffraction grating?

4. You are given two diffraction gratings, one with 400 lines per centimeter and the other with 4000 lines per centimeter. Which grating yields more orders of images of an illuminated slit?

5. What advantage is realized by increasing the number of ruled lines per centimeter of grating surface?

Questions GROUP B

6. Explain why the following appear red: (a) glowing charcoal, (b) a ripe cherry, (c) a neon sign, (d) the sunrise, (e) objects viewed through red sunglasses .

7. How can you explain that in observations of thin films by reflected light the interference effects are the reverse of those we would normally expect?

8. You are given two optical gratings, one with fewer lines per centimeter than the other, and a single monochromatic light source. For which grating will the angular separation of orders be greater? Justify your conclusion.

9. What part of Young's double-slit experiment depended on diffraction and what part depended on interference?

Problems GROUP A

1. A transmission grating with 5800 lines/cm is illuminated by monochromatic light with a wavelength of 4920 A. What is the diffraction angle for the first-order image?

Assignment 38 Page 378

Questions GROUP A

1. 1. What phenomenon provides evidence of the transverse wave character of light?

2. How do Polaroid sunglasses reduce the glare of bright sunlight?

3. Distinguish between a structural color and a pigment color.

4. Define the polarizing angle.

5. How could you determine whether a beam of light is plane polarized or unpolarized?

6. Suggest a way to identify the polarizing axis of a sheet of Polaroid film.

Questions GROUP B

7. Explain why a Polaroid disk used as an analyzer blocks the beam of light transmitted by the polarizer disk when it is properly oriented.

8. The two beams of light that emerge from a doubly refracting crystal travel through the crystal at different speeds. Can they be made to produce an interference pattern? Explain.

9. A physics student observes that setting sun near the horizon is while the skylight overhead is blue. Explain.

10. For a given optically active substance upon what does the magnitude of the rotation angle for the plane of polarized light passing through the stance depend?

11. If scattering of sunlight is more pronounced in the shorter wavelength regions, violet light must be scattered more than blue. Why does the sky appear to be light blue rather violet?

12. A tube filled with a sucrose solution is placed between two crossed polarizing disks. (a) Explain why some light is transmitted through the analyzer. (b) In what direction must analyzer be rotated to reduce the light intensity to a minimum? (c) The tube is now filled with a more dilute solution of the same substance. How must the analyzer be adjusted to establish the light minimum?

No Problems this time.

Assignment 39 Page 392

Questions GROUP A

1. List five examples (other than those given in this chapter) in which electrification occurs.

2. A hard rubber rod is rubbed with fur (kitteee). What kind of charge is acquired (a) by the rubber rod, (b) by the fur?

3. A glass rod is rubbed with silk. What kind of charge is acquired (a) by the glass rod, (b) by the silk?

4. A pith ball suspended on a silk thread is attracted to a charged rubber rod. Does this indicate that the pith ball is oppositely charged? Explain.

5. State the law of electrostatics that reveals the nature of the attraction repulsion of charged objects.

6. Why do the leaves of an electroscope diverge when a object is brought near?

7. Why is it necessary to ground an electroscope temporarily while inducing a residual charge on it with a negatively charged object?

8. What determines the property of a metal as a conductor of electricity? Hint: Remember the metallic bond.

9. Explain why sulfur is a very poor conductor. Hint: Remember the covalent molecular bond.

10. What is the unit of electric charge?

11. State Coulomb's law of eiectrostatics.

12. Define an electric field.

Questions GROUP B

13. How can you explain (a) the presence of a charge on a rubber rod after it has been rubbed with fur, (b) the charge remaining on the fur?

14. Which do you think offers the more conclusive proof of the presence of a charge on a pith-ball electroscope: an observed force of repulsion on it or one of attraction? Explain.

15. Given a charged sphere, describe a simple experiment that would enable you to determine conclusively the nature of the charge on the sphere.

16. A negatively charged rod is brought near the knob of a charged electroscope. The leaves first collapse and then as the rod is brought nearer they again diverge. (a) What is the residual charge on the electroscope? (b) Explain the action of the leaves.

17. (a)In order for a coulomb force to be expressed in newtons, what must be the dimensions of the proportionality constant in the Coulomb's law equation, F = kQ1Q2d2?, (b) Verify your answer.

18. A very small sphere is given a positive charge and is then brought near a large negatively charged plate. Draw a diagram of the system showing the appearance of the electric lines of force.

19. An electron of mass m and charge e- is projected into a uniform electric field with an initial velocity v1 at right angles to the field. Describe its motion in the electric field.

Problems GROUP B

1. A Small sphere is given a charge of +20 mc and a second sphere of equaldiameter located 10 cm away is given a charge of -5.0 mc. What is the force of attraction between the charges?

2. The two spheres of Problem 1 are allowed to touch and are again spaced 10 cm apart. What force exists between them?

Assignment 40 Page 407

Questions GROUP A

1. In what region of an insulated ellipsoidal conductor is the greatest charge concentrated?

2. What determines whether a difference of potential exists between two points?

3. Define (a) potential difference, (b) the unit of potential difference.

4. A conducting object connected to the earth is at zero potential. Explain.

5. Is work required to move a charge along the surface of a charged conductor isolated in space? Explain.

6. How does a spark discharge occur between two charged surfaces?

7. (a) Define capacitance. (b) What is the unit of capacitance?

8. What is the effect of connecting capacitors (a) in parallel, (b) in series?

Questions GROUP B

10. (a) Why is it not possible to maintain a charge on an electroscope indefinitely? (b) What shape should the knob have for a minimum rate of loss of charge?

11. Why are the tips of lightning rods shaped into sharp points?

12. Why are the occupants of a steelframe building not harmed when the building is struck by lightning?

13. Would you expect to be very successful in conducting experiments static electricity on a humid day? Explain.

14. The electrostatic force between charges immersed in oil is found be one half of the electrostatic force when the same two charges are air. Explain.

15. A solid metal sphere and a hollow metal sphere have the same dimensions, both perfectly insulated. Which will hold the larger maximum charge in air without breaking down?

Problems GROUP A

1. 1. A capacitor with air as its dielectric has a capacitance of 150 pf. What is its capacitance when the air is replaced by mica? See Table 16-1 for values of dielectric constants.

2. A 5.0 mf capacitor, C1, and a 7.5 mf capacitor, C2, are connected in parallel across a 28-v battery. What charge is stored in each capacitor?

3. (a) Capacitors C1, C2, and C3, of capacitances 2.00 mf , 4.00 mf , and 5.00 mf , respectively, are connected in parallel. (a) What is their total capacitance? (b) When these three capacitors are connected in series, what is their total capacitance?

4. A 5.0 mf capacitor is charged to a potential difference of 28 v. What is the charge on the capacitor?

5. The potential difference across the plates of a 2.70 mf capacitor is 150 v. What charge is stored in the capacitor?

Assignment 41 Page 423

Questions GROUP A

1. What is an electric current?

2. What is the unit of current?

3. Define the unit of current in terms of :fundamental units.

4. What is electric resistance?

5. Name five basic sources of continuous current.

6. Name a current-producing device for each of these sources.

7. What are the essential parts of a primary cell?

8. Define an electrolyte.

9. What term is used to identify (a) the negative electrode of an electric cell, (b) the positive electrode?

10. What is the distinguishing characteristic of direct-current electricity?

11. Distinguish between the terms ''open circuit" and "closed circuit."

12. What is the open-circuit potential difference of a source of current called?

Questions GROUP B

13. What change in the energy of an electron is produced (a) by a source of emf, (b) by a load connected across a source of emf?

14. Both primary and storage cells are sources of emf. What distinguishes one cell from the other?

15. What determines the efficiency with which heat is converted to electricity in thermoelectric converters?

16. Distinguish between potential difference and emf.

17. (a) How would you connect 1.5volt dry cells to provide a 6-volt battery to supply a continuous current of0.25 ampere to a load? (b) Draw a diagram circuit of the battery you describe.

Assignment 42 Page 442

Questions GROUP A

Hint: Laws of Electric Circuits.

Hint: Laws of Resistance.

1. State Ohm's law (a) verbally, (b) mathematically.

2. What is the mathematical expression for Ohm's law as it applies to a part of a circuit that does not contain a source of emf?

3. What is the identifying characteristic of a series circuit?

4. State the three cardinal rules for circuits in which resistances are in series. Hint: Kirchoff's Series Law.

5. Define a parallel circuit.

6. What change occurs in the total resistance of a circuit as additional resistances are added (a) in series, (b) in parallel?

7. State the three cardinal ntles for circuits in which resistances are connected in parallel. Hint: Kirchoff's Current Law.

8. (a) What is the usual relationship between resistance and temperature of metallic conductors? (b) Is this true of all conducting materials in general?

9. How does the resistance of a conductor vary with its length?

10. What is the relationship between the resistance of a conductor and its cross-sectional area?

11. Define the resistivity constant, rho, that appears in the mathematical expression for the laws of resistance.

12. Demonstrate that resistivity, rho, has the dimensions "ohm-centimeter."

Questions GROUP B

15. Why are lamps in a house-lighting circuit not connected in series?

16. What would happen if a 6-volt lamp and a 120-volt lamp were connected in parallel across a 120-volt circuit?

17. Draw a diagram of an electric circuit that would be classified as a simple network. Include the internal resistance of the source of emf. Assign values to all resistances and to the source of emf.

18. Explain how the voltmeter-ammeter method is used for measuring resistance.

Problems GROUP A

... Refer to Appendix B, Tables 20 and 21

1. A resistance of 18 ohms is connected across a 4.5-volt battery. What is the current in the circuit?

2. The load across a 12-volt battery consists of a series combination of three resistances, R1, R2I and R3,that are 15 ohms, 21 ohms, and 24 ohms respectively. (a) Draw the circuit diagram. (b) What is the total resistance of the load? (c) What is the magnitude of the circuit current?

3. What is the potential difference across each of the three resistances of Problem 2?

4. A small lamp is designed to draw 300 ma in a 6.0 v circuit. What is the resistance of the lamp filament?

6. The resistance of an electric lamp filament is 230 ohms. The lamp is switched on when the line voltage is 115 volts. What current is in the lamp circuit?

7. If the line voltage of Problem 6 rises to 120 volts, what current is in the lamp circuit?

10. Two resistances, one 12 ohms and the other 18 ohms, are connected in parallel. What is the equivalent resistance of the parallel combination?

14. A 3.0 ohm, a 5.0 ohm, and an 8.0 ohm resistance are connected in parallel. What is the equivalent resistance?

16. A 24-volt lamp has a resistance of 8.0 ohms. What resistance must be placed in series with it if it is to be used on a 117 volt line?

Assignment 43 Page 456

Questions GROUP A

Hints: Chapter 18 Formulae

1. State four ways in which the work done by an electric current in a load may be observed, and name the kind of load responsible in each instance.

2. Equal lengths of silver wire and iron wire having the same diameters are connected in series to a dry cell form the external circuit across a dry cell. Which wire becomes hotter? Explain.

3. One length of platinum wire is connected across the terminals of a dry cell. A second platinum wire identical with the first, is connected across a battery of two dry cells in series. Which wire becomes hotter? Explain.

4. State Joule's law.

5. How may electric power be defined?

6. (a) What change occurs in the heating effect of an electric circuit if the source of emf remains the same but the total resistance is cut in half? (b) Devise a simple circuit problem to prove your answer.

7. If a battery is short-circuited by means of a heavy copper wire, its temperature rises. Explain.

8. Under what circumstance is the power expended in a load the maxi:mum the source is able to deliver?

9. Suppose you have just paid the electric utility bill for your home. (a) What did you purchase? (b) In what units was it measured? Hint: The meter reads "kilowatt.hours". A watt is a joule/sec, an hour is 60 seconds. Do your units.

10. What change occurs in the resistance in the external circuit connected to a source of emf when the load across the source is increased?

Problems GROUP A

1. The current in an electric heater is 7.5 a. What quantity of electric charge nows through the heater in 15 min?

2. Determine the current in a lamp circuit if 4800 c of electric charge flows through the lamp in 25 min.

3. An electric lamp connected across a 117 v line has a current of 0.52 a in it. How much work is done in 12 min?

4. What is the approximate wattage rating of the lamp in Problem 3?

5. How many kilocalories of heat are produced by a resistance of 55 W connected across a 110-v line for 10 min?

6. A heating coil across a 117 v line draws 9.00 a. How many kilocalories are liberated if the heater operates for 30.0 min?

7. The heating element of an electric iron has a resistance of 24 W and draws a current of 5.0 a. How many kilocalories are developed if the iron is used for 45 min?

8. A battery has an emf of 26.4 v and an internal resistance of 0.300 W. A load of 3.00 W is connected across the battery. How much power is (a) delivered to the load, (b) dissipated in the battery?

9. (a) To what value would the load resistance of Problem 8 have to be changed in order that maximum power is delivered to the load using the same source of emf? (b) What is the magnitude of the maximum power delivered to this load? (c) What power is now dissipated in the battery?

10. A wire for use in an electric heater has a resistance of 5.25 W. What length of this wire is needed to make a heating element for a toaster that will draw 8.70 a across a 120-v line?

Problems GROUP B

11. If electric energy costs 9.24 per kw hr, what is the cost of heating 4.6 kg of water from 25 oC to the boiling point, assuming no energy is wasted?

13. Why is it important that an automobile battery have a very low internal resistance?

Assignment 44 Page 463

Questions GROUP A

1. How can electron-transfer reactions that are not spontaneous be forced to occur?

2. What is an electrolytic cell?

3. What may be the effect of the conduction of electric charge through a ionic compound?

4. What are the basic requirements for a silver-plating cell?

5. Why is electrolytically refined copper used to make electric conductors?

6. State Faraday's laws of electrolysis.

7. What part of a silver coulombmeter is used as the cathode?

8. Distinguish between an electrochemical cell and an electrolytic cell.

9. Compare the cathode and anode reactions in an electrolytic cell with the corresponding electrode reactions in an electrochemical cell.

10. The g-at wt of aluminum is 27, and the g-at wt of gold is 197; both ions have a charge of 3. Which has the higher electrochemical equivalent?

11. Show that the mass of an element deposited according to Faraday's law can be expressed in grams.

12. How could you define the ampere in relation to Faraday's laws and the silver coulombmeter?

Problems GROUP A

1. How much silver can be deposited in 8 min by making use of a constant of 0.500 a?

2. An electroplating cell connected a source of direct current for 15.0 min deposits 0.750 g of copper. What is the average current in the cell

5. How many hours would it take to plate 25.0 g of nickel onto an automobile bumper if the current in the plating bath is 3.40 a?

Assignment 45 Page 476

Questions GROUP A

1. 1. (a) What is a lodestone? (b) Why are lodestones sometimes called natural magnets?

2. What is the distinguishing property of ferromagnetic materials?

3. Distinguish between diamagnetic and paramagnetic materials.

4. What two kinds of electron motion are important in determining the magnetic property of a material?

5. What are electron pairs and what is their significance in regard to magnetic character?

6. (a) What three metals are the most important ferromagnetic materials? (b) What special alloy is often used to make very strong magnets?

7. How can you account for the ferromagnetic properties of the metals of the Iron Family?

8. What are magnetic domains?

9. Describe the condition of a ferromagnetic material in a state of magnetic saturation.

10. State Coulomb's law for magnetism.

11. Under what circumstances will a magnetic force be (a) one of repulsion, (b) one of attraction?

12. Describe a simple way to examine fields of small magnets.

13. What is the advantage in making a magnet in the shape of a horseshoe?f

14. Describe an experiment that induced magnetism.

15. Distinguish between a north pole and the north magnetic pole.

16. Why is a declination angle involved in the use of a compass over most the earth's surface?

Questions GROUP B

17. Explain, on the basis of atomic stucture, the property of diamagnetism.

18. Explain paramagnetism on the basis: of imbalance between orbits and spins.

19. Assume the dish in Figure 19-8 to located in the northern hemisphere. Will the magnetized needle be attracted to the north edge of the dish? Explain.

20. How would you prove that a steel bar is magnetized?

21. If a watch mechanism is to be magnetically "insulated," should the be made of diamagnetic, paramagnetic, or ferromagnetic material? Explain.

No Problems here.

Assignment 46 Page 487

Questions GROUP A

1. What important discovery was made by Oersted?

2. A conductor carrying a current is arranged so that electrons flow in one segment from north to south. If a compass is held over this segment of the wire, in what direction is the needle deflected?

3. Describe a simple experiment to show the nature of the magnetic field about a straight conductor carrying a current.

4. Suppose an electron flow in a conductor passing perpendicularly through this page is represented by a dot inside a small circle when the direction of flow is up out of the page. What is the direction of the magnetic flux about this current? Hint: The Left Hand Rule.

5. Upon what factors does the strength of an electromagnet depend?

6. What prevents the movable coil of a galvanometer from aligning its magnetic field parallel to that of the permanent magnet each time a current is in the coil?

7. (a) Why is it necessary that an ammeter be a low-resistance instrument? (b) Why must a voltmeter be a high resistance instrument?

Questions GROUP B

8. A solenoid with ends marked A and B is suspended by a thread so that the core can rotate in the horizontal plane. A current is maintained in the coil such that the electron flow is clockwise when viewed from end A toward end B. How will the coil align itself in the earth's magnetic field?

9. A stream of electrons is projected horizontally to the right. A straight conductor carrying a current is supported parallel to the electron stream and above it. (a) What is the effect on the electron stream if the direction of the current in the conductor is from left to right, (b) if the current is reversed?

Problems GROUP B

1. Two parallel conductors 2.0 m long and 1.0 m apart and carrying equal currents experience a total force of 1.6 x 10-6 n. What magnitude of current is in each conductor?

2. An ammeter that has a resistance of 0.01 ohm is connected in a circuit and indicates a current of 10 amperes. A shunt (Shuuuuunnnt) having a resistance of 0.001 ohm is then connected across the meter terminals. What is the new reading on the meter? Assume the introduction of the shunt does not affect the total circuit current.

3. A galvanometer has a zero-center scale with 20.0 divisions on each side of zero. The pointer deflects 15.0 scale divisions when a current of 375 ma is in the movable coil. (a) What is the current sensitivity of the meter? (b) What current will produce a fullscale deflection?

Assignment 47 Page 498

Questions GROUP A

1. What is the essential condition under which an emf is induced in a conductor?

2. What determines the magnitude of the emf induced in a length of conductor moving in a magnetic field?

3. In what two ways may the rate of change of magnetic flux linking a conductor be increased?

4. Distinguish between an induced emf and an induced current.

5. What is the source of the energy expended as work is done in a load by an induced current resulting from the movement of the conductor in a magnetic field?

6. State Lenz's law. (Ohhh, the Drop Zone).

Hint: E = -NDf/Dt, where E = induced emf, N = number of turns, Df = change in megnetic flux, Dt = time change.

7. What is the meaning of the negative sign in the expression E = -NDf/Dt?

1. A coil of 325 turns moving perpendicular to the flux in a uniform magnetic field experiences a change in flux linkage of 1.15 x 10-5 weber in 0.00100 s. What is the induced emf?

2. How many turns are required to produce an induced emf of 0.25 volt for a coil that experiences a change in flux linkage at the rate of 5.0 x 10-3 weber per s?

Assignment 48 Page 514

Questions GROUP A

1. What are the essential components of an electric generator?

2. State the rule that helps us determine the direction of the induced current in the armature loops of a generator.

3. Distinguish between a direct current and an alternating current.

4. Under what circumstances does a simple generator produce a sine-wave variation of induced voltage?

5. What does the term q (theta) represent in the expression e = Emax sin q?

6. (a) What is a magneto? (b) For what is it used?

7. What is the function of an exciter in the generation of a-c power?

8. (a) What is meant by the frequency of an alternating current? (b) Under what circumstances will the frequency of a generated current be the same as the rps of the armature?

9. How can a generator be made to supply a direct current to its external circuit?

10. In what way is the output of a d-c generator different from the d-c output of a battery?

11. (a) What methods are used to energize the field magnets of d-c generators? (b) Draw a circuit diagram of each method.

12. What are the three power-consuming parts of a d-c generator circuit?

13. What is meant by the term a (alpha) in the torque expression T = Fw cos a ?

14. State the rule that helps us the direction of motion of the ture loops of a motor.

15. (a) What is meant by back emf? (b) How is it induced in an motor?

16. What two quantities influence amount of torque produced in a motor?

17. What are the three common a-c motors?

Questions GROUP B

18. What is the advantage of having or 6-pole field magnet in a producing a 60-hz output?

19. How does an increase in the a series-wound d-c generator the induced emf? Explain.

20. How does an increase in the load a shunt-wound d-c generator the induced emf? Explain.

21. How is torque produced on the ture loops of a motor?

22. Why is it true that an operating motor is also a generator?

23. The torque in a series motor increases as the load increases. Explain.

24. Explain why a single-phase induction motor is not self-starting.

25. Why are synchronous motors used in electric clocks?

26. Two conducting loops, identical except that one is silver and thethe other is aluminum, are rotated in a field. In which case is the larger torque required to turn the loop?

Prtoblem GROUP A

1. A series-wound d-c generator turning at its rated speed develops an emf of 28 v. The current in the external circuit is 16 a and the armature resistance is 0.25 W. What is the potential drop?

Assignment 49 Page 522

Questions GROUP A

1. Define (a) mutual inductance, (b) self-inductance .

2. What types of losses occur in a transformer?

3. What is the effect on the inductance of a coil when an iron core is inserted?

4. Why is a closed core used in a power transformer?

5. If an ideal transformer triples the voltage, how does the secondary current compare with the primary current?

Questions GROUP B

6. Why is an inductor in an electric circuit said to impart a flywheel effect?

7. Why is a transformer considered to be an a-c circuit device?

8. The primary of a step-up with negligible losses is a source of emf and the connected to a resistance load. What is the relationship between and secondary (a) current, (b) and (c) number of turns?

9. Explain why the galvanometer Figure 20-32 indicates a current in secondary at the time the key in primary circuit is closed or but not while it remains closed.

10. The voltage induced across the secondary of an ideal transformer is ten times the voltage applied across the primary. Explain why there is no power gain in the secondary.

Problems GROUP B

1. A pair of adjacent coils has a mutual inductance of 1.06 h. Determine the average emf induced in the secondary circuit when the current in the primary circuit changes from 0.00 a to 9.50 a in 0.0336 s. Hint: L = DI / Dt, Where L is inductance in henrys, I is current in amperes, and t is time in seconds.

3. A step-up transformer is used on a 120-v line to provide a potential difference of 2400 v. If the primary has 75 turns, how many turns must the secondary have (neglecting losses)? Hint: Turns ratio action: Vs / Vp = Ns / Np ,Where V = voltage, N = number of turns, s = secondary, and p = primary.

8. A transformer with a primary of 480 turns is connected across a 120 v a-c line. The secondary circuit has a potential difference of 3000 v. The secondary current is 60.0 ma and the primary current is 1.85 a. (a) How many turns are in the secondary winding? (b) What is the transformer efficiency? Hint: Turns ratio action: Is / Ip = Np / Ns ,Where I = amperage, N = number of turns, s = secondary, and p = primary.

Assignment 50 Page 542

Questions GROUP A

1, What is the significant relationship between an alternating current and alternating voltage that are in phase?

2. In a-c circuits what type of load has a current in phase with the voltage across it?

3. What is meant by instantaneous power?

4. Upon what property of an alternating current is its effective value based?

5. Define the effective value of an alternating current.

6. What is the phase relation between (a) the current in a pure inductance and the applied voltage, (b) the current and the induced voltage, (c) the applied voltage and the induced voltage?

7. Express power factor (a) in terms of the phase angle, (b) in terms of V and VR (c) What is the significance of the power factor pertaining to an a-c circuit?

8. Why is reactance described as being nonresistive?

9. (a) Define impedance. (b) Draw an impedance diagram for an inductor with reactance XL and resistance R. (c) Draw an impedance diagram for a capacitor with reactance Xc and resistance R..

10. Describe the difference in the performance of a capacitor in a dc and in an a-c circuit.

11. What is the power factor of an cuit containing (a) pure (b) pure resistance, (c) pure capacitance?

12. Express Ohm's law for an a-c (a) that includes a source of emf (b) that does not include a source of emf.

Questions GROUP B

13. Explain why the instantaneous curve for current in a resistive load varies between some positive maximum value and zero.

14. Demonstrate algebraically that the heating heating effect of an electric current is proportional to the effective current squared.

Problems GROUP A

1. A current in an a-c circuit measures 5.5 a. What is the maximum instantaneous magnitude of this current?

2. A capacitor has a voltage rating of 450 v maximum. What is the highest rms voltage that can be impressed across it without danger of dielectric puncture?

3. The emf of an a-c source has an effective value of 122.0 v. Determine the instantaneous value when the displacement angle, q, is 50.0o?

4. An alternating current in a 25.0 w resistance produces heat at the rate of 250 w. What is the effective value (a) of current in the resistance, (b) of voltage across the resistance?

5. An inductor has an inductance of 2.20 h and a resistance of 220 W. (a) What is the reactance if the a-c frequency is 25.0 hz? (b) Draw the impedance diagram and determine graphically the magnitude and phase angle of the impedance.

6. A 2.00 mf capacitor is connected across a 60.0 hz line and a current of 167 ma is indicated. (a) What is the reactance of the circuit? (b) What is the voltage across the line?

7. A capacitance of 2.65 mf is connected across a 120 v line and is found to draw 120 ma. What is the frequency of the source?

8. When a resistance of 4.0 W and an inductor of negligible resistance are connected in series across a 110 v, 60 hz line, the current is 20 a. What is the inductance of the coil?

Assignment 51 Page 549

Questions GROUP A

2. Define series resonance.

3. What is the relation between the voltage across a series L-R-C circuit and the current in the circuit at a frequency below the resonant frequency? Explain.

4. What is the relation between the voltage across a series L-X-C circuit and the circuit current at a frequency above the resonant frequency? Explain.

5. What factor largely determines the sharpness of the rise of current near the resonance frequency in a series resonant circuit?

6. What is the advantage of a resonant circuit having a high Q ?

7. How is the Q of a resonant circuit affected by an increase in (a) resistance, (b) inductance, (c) frequency?

Questions GROUP B

8. How can the resonant frequency of an L-R-C circuit be varied?

9. What would be the effect of having an inductor connected in series with a lamp in an a-c circuit? Explain.

10. A variable capacitor is connected in series in the circuit of Question 9 and when adjusted, the lamp glows normally. Explain.

11. A series L-R-C circuit is connected across an a-c signal source of variable frequency. Draw a curve to show the way in which the circuit current varies with the frequency of the source.

12. An a-c circuit has a low power factor because of an inductive load. (a) What is the effect of this low power factor on the circuit (b) Suggest a way to raise the factor closer to unity.

Problems GROUP B

1. A resonant circuit has an inductance of 320 mh and a capacitance of 80 pf. What is the resonant frequency?

3. The variable capacitor used to tune broadcast receiver has a maximum pacitance of 350 pf. The lowest frequency to which we wish to tune receiver is 550 khz. What value of inductance should be used in the resonant circuit?

4. The minimum capacitance of the able capacitor of Problem 3 is 15 pf.. What is the highest resonant that may be obtained from the circuit?

Assignment 52 Page 564

Questions GROUP A

1. What device is primarily responsible for the development of electronics as a branch of engineering?

2. What discovery by Joseph Thomson provided the explanation for the Edison effect?

3. What significant advantage was realized with De Forest's triode that had not been possible tlrith pleviously developed diodes?

4. (a) Define thermionic emission. (b) What type of emitter is used in receiving tubes?

5. Why is the grid of a triode called control grid?

6. What is meant when a vacuum tube is said to be cut off?

7. Why is the control grid of a tube normally maintained at negative potential with respect to cathode?

Questions GROUP B

8. Suggest two possible reasons Edison did not offer an explanation for the phenomenon known as the Edison effect..

9. Explain voltage inversion between the control grid and plate in a vacuum tube circuit.

10. What is the electron gun of a cathode-ray tube?

11. What is the basic difference between the electrostatic and electromagnetic deflecting systems used in cathode ray tubes?

12. (a) Explain why the first secondary emission electrode of a photomultiplier tube is maintained at a positive (less negative) potential with respect to the photoemission electrode. (b) Explain why each successive secondary-emission electrode is at a positive potential with respect to the preceding electrode?

Assignment 53 Page 578

Questions GROUP A

1. What is the property of a semiconductor crystal known as the diode characteristic?

2. Why is N-type germanium referred to as electron-rich germanium?

3. Why is P-type germanium referred to as hole-rich germanium?

4. What is the P-N junction of a semiconductor?

5. How are the two types of junction transistors designated?

6. Draw the circuit symbol for an N transistor. Label the emitter, base, and collector.

7. Draw the circuit symbol for a P-N-P, transistor. Label the emitter, base, and collector.

8. What is the significance of the head at the emitter in a transistor cuit symbol?

9. Which sections of a junction transistor are equivalent to the cathode, control grid, and plate of a vacuum triode?

10. What are the different circuit configurations used for transistor service?

Questions GROUP B

11. Distinguish between a germanium diode and a germanium transistor.

12. Distinguish between a P-N-P transistor and an N-P-N transistor.

13. The emitter of an N-P-N transistor is biased negatively and the emitter of a P-N-P transistor is biased positively with respect to the base. In both cases they are described as forward bias. Explain.

14. What is the alpha characteristic of a transistor and to what transistor configuration does it apply?

15. Why must the current gain in a common-base transistor circuit always be less than unity?

16. Which transistor circuit configuration mosf closely resembles the basic vacuum triode circuit? Explain why. 17• To what does the beta characteristic of a transistor refer?

18. How can you account for amplification in a common-base transistor circuit when the collector current in the output circuit can never be as large as the emitter current in the input circuit?

l9. Photovoltaic action is a type of photoelectric effect. How do the two actions differ?

20. Suggest a reason for the exposed layer of a solar cell being so thin that most of the incident photons will penetrate the layer and be absorbed by atoms in or very near the P-N junction layer.

Assignment 54 Page 590

Questions GROUP A

1. (a) Why are cathode rays so called? (b) What is the relationship between cathode rays and electrons?

2. (a) Who is credited with the discovery of the electron? (b) Describe his experiments and conclusions.

3. (a) Describe two ways in which the mass of the electron can be determined. (b) Which way is more precise?

4. In what two ways was the charge placed on the oil drops in experiment?

5. What difficulties are encountered in measuring the size of the electron?

6. Is an electron a particle or a wave? Explain your answer.

7. What is the relationship orbital of an electron and an electron shell?

8. (a) How does the mass of an electron compare with the total mass of a hydrogen atom? (b) What does this signify?

Assignment 55 Page 598

Questions GROUP A

1 .Compare the relative masses, charges, and sizes of the following particles: molecule, atom, electron, proton, neutron, nucleus.

2. Distinguish between atomic mass and gram-atomic weight.

3. (a) What do the isotopes of an element have in common? (b) How do. they differ?

4. Define the following: (a) A, (b) Angstrom, (c) Z (d) N, (e) u, (f) Mev.

5. Copy and complete the following table on a separate sheet of paper:

Questions GROUP B

6. (a) How did Rutherford obtain alpha particles? (b) How did he detect tthem after they had passed through the metal foils?

7. (a) What did the experiments of Perrin and Rutherford have in common? (b) Of Rutherford and Chadwick?

8. How did Rutherford know that the alpha particles that rebounded did not rebound from the electrons in metal foils?

9. What is the general relationship between the atomic number of an atom and the number of its isotopes?

10. (a) What is meant by nuclear mass defect? (b) What is nuclear binding energy? (c) How are they related?

11. What element has the highest Mev/nucieon?

Problems GROUP A

Note: Consult Appendix B, Table 23, for the atomic masses of nuclides:

1. (a) Calculate the mass in grams of an atom of an isotope of iron that has an atomic mass of 55.9349 m. (b) What is the mass number of this isotope?

2. The mass of an atom of an unstable isotope of neon is 3.818 x 10-23 g. (a) What is its atomic mass? (b) Its mass number?

3. A calcium ion has 20 protons, 20 neutrons, and 18 electrons. What is the magnitude of its charge in coulombs? Hint: 1 unit of charge = 1.602 x 10-19 coulombs.

4. (a) What is the atomic number of a zinc atom composed of 30 protons, 34 neutrons, and 30 electrons? (b) What is the mass number of the atom?

5. What particles, and how many of each, make up an atom of silver (atomic number 47, mass number 109)?

Assignment 56 Page 611

Questions GROUP A

Note: Consult Appendix B, Table 23 above for the atomic masses of nuclides.

1. (a) How was radioactivity discovered? (b) By whom was it discovered?

4. Give another name for (alpha particles, (b) beta particles, (c) gamma rays.

5. In a nuclear equation, (a) what do the letter symbols represent, (b) what do the subscripts indicate, (c) what do the superscripts indicate?

6. (a) What is a nuclear transformation? (b) Describe two ways in which it can occur.

7. (a) Define half-life. (b) How is half-life used to find the decay constant of a radioactive nuclide? (c) Define the various units associated with radioactivity.

8. What important conclusion was drawn from the experimental work of Cockcroft and Walton?

9. Why are neutrons more effective than other particles for bombarding nuclei?

10. (a) What is the purpose of a nuclear moderator? (b) List two substances that are used as moderators.

11. (a) How many chemical elements are known today? (b) How many of them occur naturally?

12. (a) Write the equation for the reaction that is believed to be responsible for the energy of the stars. (b) How is the mass of a star affected by this process?

13. What quantities are balanced in a balanced nuclear equation?

14. (a) What are cosmic rays? (b) What is known about their source?

Questions GROUP B

15. How can a magnet be used to identify the radiations from a radioactive substance?

l6. List three differences between gamma rays and other radioactive emissions.

l7. (a) What is the source of the energy released in a nuclear reaction? (b) Give a specific example.

18. How does the slability of a nucleus vary with (a) mass, (b) the protonneutron ratio?

19. (a) What is the difference between theaverage life of a radioactive nuclide and its half-life? (b) What is the relationship between the average life of a nuclide and its half-life?

20• (a) Suggest a way in which 80Hg200 (Mercury) might be changed into 79Au196 (gold). (b) Write nuclear tions for the reactions that are required.

21. Write the nuclear equations for alpha decay of (a) 90Th234, (b) 92U234, 83Bi214 (d) 84Po210.

22. Write nuclear equations showing the preparation of 94Pu239 from 92U238.

23. (a) Which nuclides have the smallest binding energy per nucleon? (b)Which have the largest binding enrgy per nucleon? (c) How does binding energy per nucleon affect the stability of a nucleus?

24. Describe the difference in the results when 92U235 and 92U238 absorb neutrons.

25. Explain, using a specific example, whether the half-life of an element tells when its nucleus will disintegrate.

26. When a radioactive nucleus disintegrates, the products have kinetic energy even though the original nucleus was at rest. What is the source energy?

Problems GROUP A

Note: Consult Appendix B, Table 23 above, for the atomic masses of nuclides.

Hint: Get mass defect, there are 931 Mev / mass unit.

1. How much energy is Mev is evolved in the decay of a 85Rn222 nucleus?

Assignment 57 Page 621

Questions GROUP A

1. (a) What conditions are necessary for a chain reaction? (b) What is meant by critical mass?

2. Describe the two types of reactions in a nuclear reactor.

3. (a) How does a nuclear reaction produce electric power? (b) What is meant by a critical reactor? (c) How can natural uranium be used in a critical reactor?

4. How does a breeder reactor differ from conventional reactors?

5. What are the similarities and differences between a nuclear power plant and a fossil-fuel plant?

6. What is the distinction between a magnetic-confinement and an inertialconfinement fusion reactor?

8. How could radioisotopes be used to determine the effectiveness of a fertilizer?

9. Estimate the age of a carbon sample showing an activity of 3 disintegrations per gram minute.

Assignment 58 Page 629

Questions GROUP A

1. (a) Why is it impossible to determine simultaneously the position and velocity of an electron? (b) What is the name of this principle? (c) Who first postulated it?

2. (a) What is quantum mechanics? (b) How is it used to explain atomic structure?

3. (a) Define the four quantum numbers of an electron. (b) What quantum number always has only two values? (c) Why?

4. (a) What is the Zeeman effect? (b) How can spectra be used to tell whether a specific example of the Zeeman effect is the result of the angular momentum of an electron or of electron spin?

5. (a) What is meant by the exclusion principle? (b) Who postulated it? (c) What led him to this conclusion?

6. How does the ionization energy of an electron affect the stability of an atom?

7. Why is the wavelength of a moving baseball undetectable while that of a much smaller and less massive electron is noticeable?

8. (a) How do matter waves differ from water waves? (b) Describe a model for de Broglie waves.

Assignment 59 Page 635

Questions GROUP A

1. (a) How does a Van de Graaff generator accelerate particles? (b) What type of particles can it not accelerate? (c) Why not?

2. (a) In what units is a particle accelerator rated? (b) Define the unit. (c) Give the ratings of a large Van de Graaff generator, a large cyclotron, and a large synchrotron.

3. Distinguish between a cyclotron and a synchrotron.

4. (a) What is the function of a drift tube in a linear accelerator? (b) Why are drift tubes made successively longer inside the accelerator?

5. One particle accelerator can accelerate electrons to a speed of 99.9% of the speed of light. Another machine can bring protons up to a speed of 10% of the speed of light. In terms of particle mass, which machine requires more energy?

6. (a) How does a cyclotron accelerate a proton? (b) How does it keep the proton inside the machine? (c) Why is it impossible for a cyclotron to accelerate neutrons?

7. Why is an intersecting storage accelerator more efficient than a single-beam accelerator?

8. Why are magnets unnecessary in a linear accelerator?

Assignment 60 Page 640

Thou Mayest Omit this Assignment.

Assignment 61 Page 649

Questions GROUP A

1. (a) Who proposed the table of subatomic particles? (b) What other scientific table does it resemble?

2. Define: (a) baryon, (b) meson, (c) lepton, (d) hadron, (e) boson.

3. (a) What is antimatter? (b) What happens when a particle collides with its antiparticle?

4. (a) List the four types of interactions in the universe in order of their increasing magnitude. (b) Name the carrier of each interaction. (c) Which of these interactions are effective only within the size range of the atomic nucleus?

5. Distinguish between a Newtonian force and a subatomic interaction.

6. (a) What are Feynman diagrams? (b) How are they used to describe subatomic interactions?

7. (a) List four kinds of conservation in subatomic interactions. (b) List two properties of matter that are not always conserved on the subatomic scale.

8. How does the conservation of baryons prevent the collapse of matter? 9. What is the relationship between symmetry and parity?

10. What is meant by a unified field theory?

11. Discuss the quark theory. Why, when and by whom was it proposed?

13. How does the quark theory avoid violations of the exclusion principle?

14. Distinguish between a unified field theory and a grand unified field theory.

15. What is the role of the gluon in the strong interaction?

16. Why are proton-decay experiments carried out underground?

Here Endeth the Portfolio Assignments for the Second Semester

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