Question

A conducting sphere of radius R = 20 cm is given a charge Q = 16 C. What is electric

field E at its centre?

(a) 3.6 × 106 N/C (b) 1.8 × 106 N/C (c) zero (d) 0.9 × 106 N/C​

Answer 1

Answer: zero.

Explanation: If we imagine a Gaussian surface at the centre of the sphere, the surface does not enclose any charge because charge resides on the outer surface of a charged sphere.

Therefore,

E • 4πr² = 0/α (where α is the permittivity of the medium)

E = 0

Answer 2

The correct answer will be option c.

• In a conducting sphere all the charge is concentrated at the surface of the sphere.

• There is no charge inside the sphere hence no field lines inside the sphere.

• Therefore,electric field inside the sphere is 0.