- #1

mattwkeller

- 17

- 0

## Homework Statement

In a physics lab we were instructed to give a positive charge to a metal cup by induction. Once we acquired the charged cup we were told to touch the inside of a cup with a proof plane (small metal washer on a glass rod used to transfer charge). Next, we used an electroscope to find out if the inside of the cup would charge the proof plane. It did not. Next we touched the outside of the charged cup with the proof plane and used the electroscope to check its charge and it did charge the proof plane. Why is this? I'm assuming it has something to do with Faraday's discoveries with the ice bucket but I can't find a good explanation for this particular case. So if someone could explain this case (charged cup, neutral object) I would appreciate it.

## Homework Equations

none?

## The Attempt at a Solution

Im thinking it has something to do with vector quantities cancelling each other out to do the geometry of the cup, but i haven't a good explanation for this experiment. I am sorry if this isn't the right forum, this is actually my first post. If not i would appreciate some advice. Thanks