# Equipotential lines in an experiment setup

1. Sep 16, 2009

### lsatwd

1. The problem statement, all variables and given/known data
The problem has two thin metal bar electrodes, one setup to be positive and one setup to be negative. A metal circular disc is placed between the two bars. Why do the equipotential lines near the edge of the bar run parallel to the bar?

The setup looks kind of like this:
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2. Relevant equations

3. The attempt at a solution
I'm unsure how to answer this question as I do not know what the circular disc in the middle represents. And how it factors into the question.

I have written in, "The lines near the edge of the bar runs parallel because electric field lines usually emerge perpendicular from the edge of conductors. And since equipotential lines, in turn, run perpendicular to E. Field lines, the equipotential line near the bar is parallel."

Aside from being a bit redundant, I feel this answer is insufficient since it doesn't seem to take the circular disc into consideration. Should the circular disc be a factor? Would the equipotential lines, closer to the circle, curve around it and no longer be parallel to the plate? Im confused.

2. Sep 16, 2009

### rl.bhat

As you go away from the bar electric field lines will either converge to or diverge from the metal disc due to induced charges. So near the disc equipotential lines are not parallel. But they are curved.