Question

So imagine the classic science experiment where you take an empty aluminium can and a rubber bar that you charge with fur.

At first, that can is electrically neutral.

Two different cases now that I want to discuss:

If I put the can on a desk made out of wood, the can will be attracted by my charged rubber bar due to influence. So the electrons in my rubber bar push away the electrons being in the can as far away as possible (the other side) and so the rubber bar only "sees" the protons.

If I put the can on a desk made out of a metal which is grounded, what happens then? Still influence? Or is the electrically neutral can now positive due to electrons escaping to ground?

Would love to hear some thoughts. Best regards

Answer 1

When a charged rod is brought near a neutral substance, opposite charges are attracted and like charges are repelled, resulting in a net attraction. If the can is placed on a grounded metal desk, excess electrons on the can can escape to the ground and make the can electrically neutral, causing it to no longer be attracted to the charged rubber bar.

Step-by-step explanation:

When a charged rod is brought near a neutral substance, the distribution of charge in atoms and molecules is shifted slightly. Opposite charge is attracted nearer the external charged rod, while like charge is repelled. Since the electrostatic force decreases with distance, the repulsion of like charges is weaker than the attraction of unlike charges, and so there is a net attraction.

Thus, a positively charged glass rod attracts neutral pieces of paper, as will a negatively charged rubber rod. Some molecules, like water, are polar molecules. Polar molecules have a natural or inherent separation of charge, although they are neutral overall. Polar molecules are particularly affected by other charged objects and show greater polarization effects than molecules with naturally uniform charge distributions.

If you put the can on a desk made out of a metal that is grounded, the can will no longer be attracted to the charged rubber bar due to influence. When the can is placed on the grounded metal desk, any excess electrons on the can will be able to escape to the ground. As a result, the can will become electrically neutral and will not be attracted by the rubber bar anymore.