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

  • #1
Fikremariam
5
11
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
 

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  • #2
vela
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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.
 
  • #3
Fikremariam
5
11
It represents the distance from the charge
 
  • #4
vela
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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?
 
  • #5
Fikremariam
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11
I didn't know that is why I asked
 
  • #6
vela
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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.
 
  • #7
Mister T
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Here's a hint: What are the SI units of the electric field?
 

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