A conducting sphere of radius 5 cm has an unknown charge. The electric field at 10 cm from the centre of the sphere is `1.8xx10^(3)NC^(-1)` and points radially inward. What is the net charge on the sphere?

Options

A. `1.8nC`
B. `2nC`
C. `1nC`
D. `1.5nC`

Answer

B

Explanation

For a conducting charged sphere, the electric field outside the sphere, `E=(1)/(4pi epsilon_(0))(Q)/(r^(2))`
`1.8xx10^(3)=9xx10^(9)xx(Q)/((0.1)^(2))`
The net charge on the sphere `Q=(1.8xx10^(3)xx10^(-2))/(9xx10^(9))`
`=2xx10^(-9)C=2nC`