Question

Consider two concentric conducting spheres. The outer sphere is hollow and the inner sphere is solid. Initially, they are given a charge $-7Q$ and a charge $-2Q$ respectively, then the charges on the outer surface and inner surface of the outer sphere is

• A. $-2Q,-7Q$
• B. $+2Q,-9Q$
• C. $-2Q,-5Q$
• D. $+2Q,+5Q$

Answer 1

The correct option is C $-2Q,-5Q$

Outer sphere is hollow and given a charge of $-7Q$
Inner sphere is solid and given a charge of $+2Q$

$\therefore$ Charge on outer surface of outer sphere
$=-7Q+2Q=-5Q$
Charge on inner surface of outer sphere $=-2Q$
Hence, option C is correct