A conductor with an inner cavity like that shown in the figu

A conductor with an inner cavity, like that shown in the figure below, carries a total charge of +4.70 nC. The charge within the cavity, insulated from the conductor. Is -7.70 nC.

Solution

a)

The inside of the cavity negative charge pulls positive charge towards it and repel negative charge from it. The negative charge moved to the inside is the equal to the positive charge in the cavity.

The charge on the inner surface of the conductor is 7.70 nC.

b)

The total charge on the conductor = negative charge on the outside + the positive charge inside

4.70 nC= 7.70 nC+Q

         Q=-3.00 nC