The Check Valve allows fluids to flow in one direction only.

Leonardo's Check Valve

The Rectifier is an electronic check valve

And we can receive these radio waves clear across the demo table (the Atlantic Ocean)
by detecting them with a spark gap connected to antennae.

The Electron Microscope uses charges to focus electrons.

Solid State LASER

The quantized energy emitted by electrons interacting
with holes creates coherent LASER light.

What the…
In just which direction does electricity flow anyway?
Gasp!
In the 1700’s, Ben Franklin arbitrarily defined charge.
Positive on glass with silk & Negative on rubber with Kitteeee.
Boom’s first Physics text used + to - and Right Hand Rules.
Then came the Edison Effect and Vacuum Tube Electronics.
In the early 20th Century, Thermionic Emission showed that it’s - to + and Left Hand Rules. The Texts were changed.
In the 1970’s, we have Solid State Electronics, the transistor and computer chips. It’s now possible to have two current carriers-- Electrons (negative) and Holes (positive carriers).

Computer Engineers blew it. They used the Hole Flow definition and they defined the symbols for solid state devices with current flowing from + to -.
So to conform to their symbolism, new texts are reverting back to the WRONG definition of current flow. + to - (in a wire).
I’ll ask you this:
What would you think if I told you that the earth is flat?

If I taught you that things roll uphill? (Mystery Spot).

If I said that the San Lorenzo River flows from North to South, but it’s current flows South to North?

Well, that’s what these people are saying, electrons flow from - to + but the current flows from + to -. They call it Conventional Current Flow.
Is there any hope!

Here Endeth Electronics