- #1

fawk3s

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I have some difficulties grasping the idea of this equation

Wp = q * E * r

Where

Wp - electrical potential energy

q - charge

E - the strength of the electric field

r - radius, or distance from the other point charge

So basically, say we have 2 point charges. One positive, and one negative, so they attract.

But I can't imagine how the work done by the moving point charge is the same we get by calculating by that formula. Because the closer the point charge gets to the other point charge, the bigger the E gets. So the electric force applied on that point charge isn't constant. Its getting bigger.

My physics textbook also says that the way to calculate the work done by the point charge in this situation is too difficult to describe in a high school textbook. But yet they still give me that equation. Why?

I can imagine the same thing with Earth and its gravitational potential energy, but the change in g (9,81 m/s2) is so small over short distances that there's no point to really observe it.

Or am I getting this whole thing wrong? Please help !

Wp = q * E * r

Where

Wp - electrical potential energy

q - charge

E - the strength of the electric field

r - radius, or distance from the other point charge

So basically, say we have 2 point charges. One positive, and one negative, so they attract.

But I can't imagine how the work done by the moving point charge is the same we get by calculating by that formula. Because the closer the point charge gets to the other point charge, the bigger the E gets. So the electric force applied on that point charge isn't constant. Its getting bigger.

My physics textbook also says that the way to calculate the work done by the point charge in this situation is too difficult to describe in a high school textbook. But yet they still give me that equation. Why?

I can imagine the same thing with Earth and its gravitational potential energy, but the change in g (9,81 m/s2) is so small over short distances that there's no point to really observe it.

Or am I getting this whole thing wrong? Please help !

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