Question

Thread for electricity.

I'm learning about electricity. All of my thoughts, doubts, and other stuff will go here.

Answer 1

Coulomb's Law \(\checkmark\).

Answer 2

I'm still confused about electric potential energy though. What in the world is that thing supposed to mean?

Answer 3

If a given charge distribution is continuous, we can use the technique of integration to find the resultant electric field at a point. A small element dQ is chosen in the distribution and the field \(dQ\) is chosen in the distribution and the field \(d\vec E\) due to \(dQ\) is calculated. The resultant field is then calculated by integrating the components of \(d\vec E\) under proper limits.

k.

Answer 4

Can anyone give me an idea of why electric potential energy is important?

Answer 5

I got its definition, but what does it represent?

Answer 6

any positive charge will go frm higher potential to lower potential

Answer 7

Because it would get repelled?

Answer 8

ya

Answer 9

and any negative charge will go frm lower potential to higher potential

Answer 10

So what exactly is electric potential energy? Is it stored?

Answer 11

ya i think yes

Answer 12

And we would be required to use the same amount of energy to bring a charge from infinite separation to that point...

Answer 13

ya

Answer 14

In gravitational potential energy, we act against the force of gravity to place something at a particular configuration. And in electric potential energy, we act against the electrostatic forces to place something at the same configuration.

But the difference between the two is that gravitational PE is 0 when the separation is 0, and the electric PE is 0 when the separation is \(\infty \).

Answer 15

ya

Answer 16

Hmm, so is electric PE the energy required to keep the same configuration?

Answer 17

ya

Answer 18

@UnkleRhaukus Hi, do you have the patience to work with simple questions with me just like Shamim is? :)

Answer 19

I just want everything to be crystal clear about electric PE before I proceed to electric potential.

Answer 20

I'm not able to see anything beyond the formulae.

If possible could you correlate with gravitational PE?

Answer 21

electric potential energy is like gravitational potential energy , its to do with the configuration, if there are two positively charged things they will have a potential energy associated with distance between them,
if we allow the things to move freely
this potential energy drops as the things move apart and the energy becomes kinetic,

if two objects are oppositely charged, then the similarity with gravity is more obvious, if the objects are released from far apart, the potential energy drops and the objects fall toward one another and speed up

Answer 22

So the difference lies in the fact that gravity is only attractive, while electrostatic force can be both attractive or repulsive?

Answer 23

yeps

Answer 24

And we only assume that \(U(\infty) = 0\) for simplicity reasons, hmm?

Answer 25

its not an assumption, its a choice, its usually the best choice,

potential energy is not a absolute quality, its is relative to where we choose zero to be, just as with a ball falling in gravity, we can set the ground state to be the centre of the earth or the the height of the dirt, of the floor boards or the roof, etc, as the ball falls (and its velocity / kinetic energy increases ) the potential energy released comes from the Change in potential, [not the absolute potential ]

Answer 26

OK.

What does "potential difference" mean?

Answer 27

OK, and the infinity to r is equivalent to 0 to h?

Answer 28

Never mind the second question.

The first one is what I was wondering about. The difference in electric potential, yes, but it's really hard to imagine and think about in such a huge system.

Answer 29

once we have chosen a zero point (say when two oppositely charged spheres are touching) all other configurations (separations) have an extra potential energy associated with it, this energy can be liberated as the objects fall to this zero potential state - gaining kinetic from the difference in potential they had when released , to when the have this kinetic energy

Answer 30

more separation -> less potential energy. yeah?

Answer 31

- I can highly recommend the 8.02 lecture series with Walter Lewin -

Answer 32

Ah, right. I watched the first lecture.

Answer 33

I'm all right with Coulomb's Law, forces, electric fields yada yada.

Oh wait, we have an OS group for 8.02.

Answer 34

oppositely charged objects Gain potential energy when separated,

(they will be moving together faster when the fall back together)