Answer to Question #159497 in Electric Circuits for Eva

Question

A hollow metal container with a small opening, standing on an insulating material, is given an electric charge. Explain how using such other apparatus as you may require, you would show that there is no charge on the inside of the container.

Answer 1

Explanation

• The device used to check the type of charge/compare charges is the Gold leaf electroscope.
• One can use it to roughly check if any charges are accumulated in the inner surface of the container.
• The apparatus can be illustrated as follows.

• After some charge is given to the sphere, a non-charged/neutral electroscope extended with a conductive probe as shown can be put inside the container.
• If any charge is present inside (say some positive charge), that will induce some opposite charge (electrons of some atoms in the electroscope system will be concentrated in the probe as a result of electrostatic attractions of opposite charges) in the probe.
• Since the electroscope was initially neutral, the corresponding opposite charges in it (the vacant atoms positively charged) will move (can simply be thought to move for the ease of understanding) to the far end of the electroscope: the gold leaves, which will indicate some repulsion between each leaf due to the gathering of like charges on them.
• This will be the same effect for any kind of charge if accumulated in the inner surface of the container.
• If this happens when performed, it proves that the container is having some amount of charge inside it.