A charge \( 1.2\times10^{-8}\,\mathrm{C} \) is uniformly distributed on the conducting sphere of radius 5 cm. The magnitude of the electric field at the centre of the conducting sphere is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → zero
On a conductor in equilibrium, all the charge sits on the outer surface and the electric field inside is zero. By Gauss's law, a Gaussian sphere of any radius \( r \lt R \) encloses no charge:
\( \displaystyle \oint \vec{E}\cdot d\vec{A} = \frac{q_{\mathrm{enc}}}{\varepsilon_0} = 0 \;\Rightarrow\; E = 0 \;\text{ for } r \lt R \)
The centre is inside the sphere, so the field there is zero. The radius and the charge do not matter.
NCERT (2026-27):
Electrostatics of Conductors – “… Consider a conductor, neutral or charged. There may also be an external electrostatic field. In the static situation, when there is no current inside or on the surface of the conductor, the electric field is zero everywhere inside the conductor. This fact can be taken as the defining property of a conductor.”