How does the IR LED and phototransistor circuit work?
if there is nothing between the infra red LED and the photo transistor, the photo transistor will close and allow current to flow through the visible-light LED.
What is the resistor's role in a circuit?
The resistors reduce the flow of electrons so the LED does not burn out.
How the final Project Warm circuit works
So now we add the PNP transistor, which does the opposite of the NPN transistor. They are both sensitive to the voltage between the resistor and the thermistor, so if one is on the other is off. Since they are connected to the LEDs, we get the "green is cold, red is hot" effect.
Segmented LED Explained
The middle prong is the shared positive terminal. The pins on either side of the middle prong are the individual negative terminals.
Why your electro-magnet gets warm
because current flows through th electro magnet really fast.
EEME Dad's comments: To be more specific - a lot of current flows through the magnet wire creating a stronger magnetic field.
its like a bucket for electricity.