Question

4a) If you move a positively charged object near an ungrounded conducting sphere, what kind of net charge (positive, negative, or neutral) does the sphere have?

4b) If you briefly attached a grounding wire to the side of the sphere near the positively charged object, what kind of net charge does the sphere have now?

4c) If you repeat this with an insulating sphere, what kind of net charge will it have when you are done?

Answer 1

4(a)The speher will have a net negative charge because of induction of the charge due to presence of positively charged object.

b)Because of the grounding the excess electrons on the surface of the sphere gets discharged to the ground.

c)First of all the insulator did not get charged through induction, however they can be charged by consuction by rubbing a charged object over it.

Grounding a charged insulator is not a good idea of discharging since there are no mobile charges on them, so the best way to discharge an inductor is to rub it with a grounded conductor.