A conducting sphere of radius 10 cm has unknown charge. If the electric field at a distance 20 cm from the centre of the sphere is `1.2xx10^(3)NC^(-1)` and points radially inwards. The net charge on the sphere is

Options

A. `-4.5xx10^(-9)C`
B. `4.5xx10^(9)C`
C. `-5.3xx10^(-9)C`
D. `5.3xx10^(9)C`

Answer

C

Explanation

Here, distance of point from the centre of the sphere, r = 20 cm = 0.2 m
Electric field, E = `-1.2xx10^(3)NC^(-1)`
As `E=q/(4piepsilon_(0)r^(2))`
`therefore" "q=(4piepsilon_(0)r^(2))E=((0.2)^(2)xx(-1.2xx10^(3)))/(9xx10^(9))=-5.3xx10^(-9)C`