# What happens to an electron when its used in a closed circuit?

Please help me to understand what happens to an electron when its used in a closed circuit.

Main Question: How can electrons within a circuit perform work i.e. illuminate a light bulb or heat a stove and not be lost or changed from one state to another? How could it just stay the same and continue on unchanged in the circuit......??

To reiterate ...I will provide a couple examples that have led to my confusion:

a) To generate an electric current you can rotate a conductor i.e. copper within a magnetic field and produce electric current if its a closed loop. - From what i understand the electrons that are flowing are knocked free from the copper wire and simply flow in a circuit because of the difference in potential that has been generated by the magnetic field. However if the electrons are lighting a bulb or heating a stove....how does the "conservation of energy" not apply? how can you generate heat and light without a change in the state of the electron?

b) Photovoltaic panels - Lets say a photon from the sun knocks an electron free from the n type and transfers it to the p type creating a flow in electricity in the panel; then this flow of electrons is then stored in a battery. If the battery is detached from the system and drained, then reattached and charged...have electrons not been removed from the system? The more i ponder this.....Perhaps its not the electron itself that is used but just the energy it carries?

What is actually happening to the electrons being used in a circuit? I have read lots of information and many forums on this concept and i can not get a clear answer.

Thanks,
Air39

Welcome to PF I guess. I see you've had bad experience with asking this question elsewhere on the internet, but fret not.

You've pretty much answered your question. Electrons are just carriers of energy, not the source of that energy themselves.

A pump driving a waterwheel is a fair enough analogy as well. In a closed system the water is just going circles, but it is transferring energy from the pump to the waterwheel.

In that sense it works much the same way as heat does. You don't see material flowing from one place to another with the exchange of heat, but it does carry that heat from one place to another.

NascentOxygen
Staff Emeritus
Electrons in a circuit are like an endless string of railroad cars, each coupled to the next. You push on one and it pushes the next, and that one pushes the next, and so on. So all you have to do is push against one and all along the line each moves on just a little, propelled by the one before it. So no electron needs to traverse the whole path from start to end before you see electricity completing the full circuit. What does the last car push against? It pushes on the first, hence the need for a complete circuit.

What is the force pushing these? It's the voltage from a voltage source of some description, connected somewhere into the circuit.

Much appreciated! This is a useful blog!!

Air39

phinds