Equipotential lines in an experiment setup

[lsatwd]

Homework Statement

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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Homework Equations

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? I am confused.

 

[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.

 

[tomcue]

Your response is correct in explaining why the equipotential lines are parallel to the bar. However, the circular disc does play a role in the setup and in the behavior of the equipotential lines.

The circular disc acts as a conductor and creates a uniform electric field between the two bars. This means that the potential difference between any two points on the disc is constant, resulting in equipotential lines that are evenly spaced and parallel to each other. This is known as a equipotential surface.

Since the circular disc is placed between the two bars, the equipotential lines near the edge of the bar will also run parallel to the bar, as they are influenced by the uniform electric field created by the disc.

In addition, the equipotential lines will curve around the circular disc, as you mentioned. This is because the electric field lines will also curve around the disc, and the equipotential lines are always perpendicular to the electric field lines.

In summary, the equipotential lines near the edge of the bar are parallel to the bar because of the perpendicular relationship between equipotential lines and electric field lines. The circular disc also plays a role in creating a uniform electric field and influencing the shape and direction of the equipotential lines.