Question

I don't understand why metals are all equipotentials when there is no charge flowing through them, and how they attain 0 potential eventually! Please help :)

Lecture 4: Electric Potential and Electric Energy

Answer 1

But you understand that the electric field inside the conductors is always zero, right?

Answer 2

Yes, I do! But, I couldn't understand how and why the free electrons in metals try to take the potential towards zero!

Answer 3

The potential doesnt drop to zero inside conductors. What happens is when the electric field has changed to 0 after the charges have redistributed themselves inside the conductor, the potential stays constant within the conductor, and its of the same value of the potential at its border. It may be zero, positive or negative.

Answer 4

Thanks :)

"Now any piece of metal, no matter how crumby or dented it is, is an equipotential.

As long as there is no charge moving inside the metal.

And that's obvious that it's an equipotential.

Because these charges inside the metal, these electrons, when they experience an electric field, they begin to move immediately in the electric field, and they will move until there is no force on them anymore, and that means they have effectively made the electric field zero.

So charges inside the conductor always move automatically in such a way that they kill the electric field inside.

If the electric field hadn't been zero yet, they would still be moving.

And so each metal that you have, no matter where you bring it, as long as there are no electric currents inside, will always be an equipotential."

This is a copy of that part of the transcript :) Could you please explain this is simpler words?

Answer 5

It means that inside conductors, no matter what happens outside, the electrons make sure the electric field is always 0 inside.

And since we know that\[ V = \int\limits\limits_{}^{} E.dl ; E = 0\]
\[V = constant\] and thats everywhere inside the conductor. Since theyre all at the same V, the conductor is an equipotential


Another way to think about it is, potential is energy you gain because of forces applied to you. But since E = 0 inside the conductor, there are no forces! So when you move from a point A inside the conductor to a point B also inside it, you get
\[V_A - V_B = constant - constant = 0\]
No force, no work!

Answer 6

Thanks a LOT! You explained it really well :) Thanks :)