Electric Field -- Potential between the ends of a 2 meter stick

[Fikremariam]

Homework Statement

The potential difference between the ends of a 2 meter stick that is parallel to a uniform electric field is 300V determine the magnitude of the electric field

Relevant Equations

E=F/q
E=K q/r square

I tried to find the charge from the formula v=k q/r and apply it to find the field but couldn't be sure

 

[vela]

Homework Statement:: The potential difference between the ends of a 2 meter stick that is parallel to a uniform electric field is 300V determine the magnitude of the electric field
Relevant Equations:: E=F/q
E=K q/r square

I tried to find the charge from the formula v=k q/r and apply it to find the field but couldn't be sure

In the formulas, $E = kq/r^2$ and $V=kq/r$, what does the variable $r$ represent? Be specific.

 

[Fikremariam]

It represents the distance from the charge

 

[vela]

More specifically, the distance from a point charge. In this problem, you're told there's a uniform field—that is constant magnitude and constant direction. Is the field of a point charge uniform?

 

[Fikremariam]

I didn't know that is why I asked

 

[vela]

But you can figure it out. Look at the formula for $E$. If you plug in different values for $r$, you don't get the same number, i.e., the magnitude changes with distance, so the field of a point charge isn't uniform. That means the formulas that apply to a point charge probably aren't useful for this problem.

I'm guessing you feel a bit overwhelmed by the many formulas for the electric field, potential energy, electric potential that you've encountered recently. It might be a good idea to write them all down on a piece of paper and note when each formula is applicable. I suggest this for two reasons: (1) when you do this, you'll probably see there aren't as many formulas as you thought there were, so the topic will seem more manageable; and (2) it's helpful to have this sheet when you're working on homework.

In this problem, you're looking for a relationship between $\Delta V$ and $E$ when $\vec E$ is uniform. Try checking the chapter summary for such a relationship.

 

[Mister T]

Here's a hint: What are the SI units of the electric field?