question_answer

Shown in the figure are two point charges +Q and -Q inside the cavity of a spherical shell. The charges are kept near the surface of the cavity on opposite sides of the centre of the shell. If \[{{\sigma }_{1}}\] is the surface charge on the inner surface and \[{{Q}_{1}}\] net charge on it and \[{{\sigma }_{2}}\] the surface charge on the outer surface and \[{{Q}_{2}}\] net charge on it then : JEE Main Online Paper (Held On 10 April 2015)

A) \[{{\sigma }_{1}}\ne 0,{{Q}_{1}}=0\] \[{{\sigma }_{2}}\ne 0,{{Q}_{2}}=0\]

B) \[{{\sigma }_{1}}\ne 0,{{Q}_{1}}=0\] \[{{\sigma }_{2}}=0,{{Q}_{2}}=0\]

C) \[{{\sigma }_{1}}\ne 0,{{Q}_{1}}\ne 0\] \[{{\sigma }_{2}}\ne 0,{{Q}_{2}}\ne 0\]

D) \[{{\sigma }_{1}}=0,{{Q}_{1}}=0\] \[{{\sigma }_{2}}=0,{{Q}_{2}}=0\]

Correct Answer: B

Solution :

                 On outer surface there will be no charge. So \[{{Q}_{2}}={{\sigma }_{2}}=0\] On inner surface total charge will be zero but charge distribution will be there so \[{{Q}_{1}}=0\,{{\sigma }_{1}}\ne 0\]