Question

A charge $Q$ is placed inside the sphere of radius $a$ then what will be the value of charge that will be accumulated on the surface of the sphere?
A. $0$
B. $Q$
C. $- Q$
D. $- 2Q$

Answer 1

Charge is a physical property of matter which causes the material to experience a force when placed in an electromagnetic field. The value of electric charge inside a conductor (in this case, sphere) is zero. Considering this information, we can figure out the value of charge on the surface of the sphere.

Complete step by step answer:

Consider the sphere shown in the figure to be the sphere asked in the question. Keeping in mind that the charge inside the sphere is $Q$ . We know that the charge inside a conductor is zero. When a charge is placed inside the conductor, a charge is induced in the inner surface of the sphere which in turn induces a charge on the outer surface of the sphere.

This induction of charge in the inner side and outer side of a sphere should cancel each other so as to get the value of the net charge inside a conductor as zero. Meaning, the charges on the inner surface of the sphere should be of equal magnitude but of opposite charge as the value of charge on the outer surface of the conducting sphere.That means that if charge $Q$ is placed inside the sphere, then a charge of $- Q$ should be on the inner surface of the sphere and a charge of $Q$ on the outer surface.

Therefore, the right answer is option B.

Note: The idea of electromagnetic induction and positive and negative charges must be memorized properly. The value of charge has to cancel each other on the surface of the conducting and the inner surface of the sphere so as to get a net charge of zero for the whole sphere.