Spheres

[Soaring Crane]

Sphere A carries a net positive charge, and sphere B is neutral. They are placed near each other on an insulated table. Sphere B is briefly touched with a wire that is grounded. Why is Sphere B now negatively charged? I mean, why isn't it positively charged (which I though was the answer) or neutral? Is it the flow of electrons from A to B?

Thanks.

[StatusX]

There is no way for charge to flow off sphere A. Grounding sphere B just allows charge to flow onto it from some unlimited source (the earth) until it is at 0 volts. In this case, the positive sphere pulls negative charge up from the ground onto sphere B.

[thomate1]

Dear friend,
When we say that B is nuetral,it means that there are equal amount of +ve & -ve charge in B. When the sphere B is grounded,the +ve charge in A attracts the -ve charges to that side.The +ve charges and -ve charges are seperated.+ve charges will flow to ground making B a -vely charged body.This phenomenon is called Induction.