Question

A hollow insulated conduction sphere is given a positive charge of 10 $\mu$C. What will be the electric field at the centre of the sphere if its radius is 2 metres?

• A. Zero
• B. $5 \mu Cm^{-2}$
• C. $20 \mu Cm^{-2}$
• D. $8 \mu Cm^{-2}$

Answer 1

Answer: (A)

Zero

Answer 2

Charge resides on the outer surface of a conducting hollow sphere of radius R. We consider a spherical surface of radius r < R. By Gauss theorem
$\int_{s}\vec{E.} \vec{d}s =\frac{1}{\varepsilon_{0}} \times$ charge enclosed or $E\times4 \pi r^{2} =\frac{1}{\varepsilon_{0}} \times0 \, \Rightarrow\quad E=0\quad$
i.e electric field inside a hollow sphere is zero.