Please solve question 11
11. A spherical conductor A contains two spherical cavities. The total charge on the conductor itself is zero. However, there is a point charge qb at the centre of one cavity and qc at the centre of the other. A considerable distance r away from the centre of the spherical conductor, there is another charge qd. Force acting on qb, qc and qd are. F1 F2 and F3 respectively. [Assume all charges are positive]
(A) F1 < F2 < F3
(B) F1 = F2 < F3
(C) F1 = F2 > F3
(D) F1 > F2 > F3
Dear Student,
The force on qb and qc is zero. The field inside the spherical cavity is quite independent of anything outside. A charge −qb is uniformly distributed over the conducting surface to cancel the field from the point charge. The same happens with qc.
This leaves an excess charge of qc + qb on the outside surface of the conductor. If qd were absent, the field outside A would be the symmetrical, radial field E, the same as a point charge because the excess charge would uniformly distribute itself over the spherical outer surface.
The influence of qd will slightly alter the distribution of the charge on A, but without affecting the total amount. Hence for large r, the force on qd will be approximately
Thus, The correct option is (B) F1 = F2 < F3
Regards
The force on qb and qc is zero. The field inside the spherical cavity is quite independent of anything outside. A charge −qb is uniformly distributed over the conducting surface to cancel the field from the point charge. The same happens with qc.
This leaves an excess charge of qc + qb on the outside surface of the conductor. If qd were absent, the field outside A would be the symmetrical, radial field E, the same as a point charge because the excess charge would uniformly distribute itself over the spherical outer surface.
The influence of qd will slightly alter the distribution of the charge on A, but without affecting the total amount. Hence for large r, the force on qd will be approximately
Thus, The correct option is (B) F1 = F2 < F3
Regards