A conducting sphere is charged. If the electric field at a distance 20 cm from the centre of the sphere is $1.2 \times 10^3 NC^{-1}$ and points radially inwards, the net charge on the sphere is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $-5.3 \times 10^{-9} C$
Using Gauss's law,
$E.4πr^2=\frac{Q}{ε_0}$
$⇒Q=E.4πr^2.ε_0$
$⇒Q=(1.8×10^3)×(4\pi (0.20)^2)(8.85×10^{-12})$
$≃-5.34nC$