A spherical conductor of radius 10 cm has a charge of 3.2 × 10−7C distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere ?

A spherical conductor of radius 10 cm has a charge of 3.2 × 10−7C distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere ?

[ \( \frac{1}{4\pi \varepsilon_0} = 9 \times 10^9 \, \text{N·m}^2/\text{C}^2 \) ]

(a) \( 1.28 \times 10^5 \, \text{N/C} \)
(b) \( 1.28 \times 10^6 \, \text{N/C} \)
(c) \( 1.28 \times 10^7 \, \text{N/C} \)
(d) \( 1.28 \times 10^4 \, \text{N/C} \)

Answer :  (a) \( 1.28 \times 10^5 \, \text{N/C} \)

E = \(\frac{kq}{r^2} = \frac{9 \times 10^9 \times 3.2 \times 10^{-7}}{(0.15)^2}\)

E = \(\frac{2.88 \times 10^3}{0.0225} = 1.28 \times 10^5 \, \text{N/C}\)