Question

How can you determine the type of charge on an object using an electroscope that has a net charge of unknown sign? Explain in connection with Triboelectric Series.

Answer 1

Triboelectric series just lists the materials which have greater tendency to become positive as well as materials which have greater tendency to become negative.

According to this effect if a neutral material is in contact with some material possessing a positive charge, then the neutral element has a tendency to become negatively charged by means of charge transfer.

Now, consider an electroscope having a net charge of unknown sign.

1. Firstly, before beginning we need to ground the electroscope by removing all the charge it is possessing. For this you can simply touch the electroscope with your hand, which would ground the electroscope, removing any excess charge.

2. Touch the object you want to find charge of with the electroscope. The electroscope leaves will rise.

3. Take a glass rod and rub it with the towel, it will acquire a positive charge.

4. Bring the glass rod and touch it to the electroscope.

5. Now if leaves repulse, the charge on unknown object was same (i.e. positive). And if the leaves repel then charge on unknown object was opposite (i.e. negative)