Question

A solid conducting sphere 60 mm in radius carries a charge of 5.3nC . A thick conducting spherical shell of inner radius 100 mm and outer radius 120 mm carries a charge of -4.0 nC and is concentric with the sphere.

A. Calculate the surface charge density on the surface of the solid sphere.

B.Calculate the surface charge density on the inner surface of the thick shell.

C.Calculate the surface charge density on the outer surface of the thick shell.

Answer 1

since the electric field inside the spherical is to be equal to zero.

so, net charge on solid sphere and inner surface of spherical shell equals zero.

so, charge on solid sphere= 5.3nC

inner surface of spherical shell charge= -5.3nC

outer surface of spherical shell charge= 1.3nC (to make net charge= -4nC).

so, a) surface charge density on solid sphere= 5.3/(4*pi*60*60) nC/mm²

= 1.17*10^-4 nC/mm²

b)surface charge density on inner surface of spherical shell= -5.3/(4*pi*100*100) nC/mm²

= 4.22*10^-5 nC/mm²

c)surface charge density on outer surface of spherical shell= 1.3/(4*pi*120*120) nC/mm²

= 7.18*10^-6 nC/mm²