Look! The LED is powering itself!
What in the world is going on here?
The idea of this circuit is not original to me. Its concept has been done at least once before here: https://everycircuit.com/circuit/5276667463860224
However, I changed some of the values and components to emphasize the effect. Flip the switch up first to connect the LED to the voltage source, then flip it back down. Current will suddenly start flowing through the LED and resistor by itself. It looks like the LED turns itself ON!
What's actually happening is that the capacitance of the PN junction is discharging. The 30V source charges up this hidden capacitor. Then, flipping the switch will cause the capacitor to discharge through the resistor and back to the other side of the LED. EveryCircuit will treat this current as powering the LED. (NOTE, this may not be a totally acceptable explanation. See comments below. This is to the best of my knowledge...)
This does not work in real life. But it's a swell trick in EC, and it may wow your friends.
Check out this circuit where I do nearly the same thing, but with a 7-segment display. https://everycircuit.com/circuit/5861787383365632
My next post uses this technique for an oscillator flashing circuit. See here for details: https://everycircuit.com/circuit/4699313716068352
