Consider two concentric conducting spheres. The outer sphere is hollow and initially has a charge Q1 = - 10Q deposited on it. The inner sphere is solid and has a charge Q 2 = + 1Q on it. 1) How much charge is on the outer surface

Q_out, shell = 9Q

Explanation:

Given:

- Q_in, shell = - 10 Q

- Q_sphere = + 1Q

Find:

How much charge is on the outer surface?

Solution:

The electric field in the material of both the sphere and shell must be zero. The only way for this to occur is if the charge inside the

inner surface of the shell is such that its charge plus the solid's charge is zero. The rest of the excess charge from the shell moves to the outside of the shell.

Hence,

Q_out, shell + Q_in, shell + Q_sphere = 0

Q_out, shell - 10 Q + 1 Q = 0

Q_out, shell = 9Q