Homework Help: Electrically Charged object

1. May 18, 2013

ShizukaSm

If I have a charged object in contact with normal air (but nothing else) and insulated, does it lose charge over time? Does the answer depend on the object being an conductor or an insulator itself?

2. May 18, 2013

cepheid

Staff Emeritus
I think the answer is typically no. In order for the object to discharge, the charges would have to travel across a very large air gap, a process that is called arcing. Air is a very poor conductor of electricity, so this just doesn't happen unless if you have a tremendous amount of static charge built up, as is the case for lightning. In order for arcing to occur, you have to have enough voltage to ionize the surrounding air, which creates a conductive pathway.

3. May 18, 2013

ShizukaSm

Thanks. I happen to be aware of arcing, but I was thinking of something less drastic, and I'm actually speaking about a realistic situation. Could somehow the particles in air slowly discharge my object?

In short, I want to know if I go to a lab tomorrow and perform this experiment (charging a sphere and connecting it through a long insulator to the ground), I can return a week later and find the same charge.

Of course, I don't have a lab so I can't actually test that.

4. May 19, 2013

ehild

You won't have the same charge on an isolated sphere the other day, and you can perform an experiment. Just rub anything plastic (I use a plastic ruler) against your hair and hang it on a thread somewhere. Initially, it attracts light things (pieces of tissue paper for example ), but it does not after a while: it loses charge. There are ions and dipole molecules in the air - water molecules are such dipoles - and they are attracted to the ruler or to your charged sphere. They might take charge over from the charged body, and then repelled by it, so they carry the charge away, into the air. In a damp day, experiments on static electricity do not work, and the teachers usually refer to the damp weather when they do not succeed to perform the experiment.

ehild