A conducting sphere fo radius 10 cm has an unknown charge. If the electric field 20 cm from the center of the sphere is `1.5xx10^(3) N//C` and points radilly inwards, what is the net charge on the sphere ?

Explanation

The electric field intensity is directed towards the centre of the sphere, which means the charge on the sphere must be negative. Moreover, the behaviour of the charged sphere for the points outside the sphere is the same as that of the point charge at its centre.
Let the charge on the sphere be Q.
The electric field intensity due to the given charged sphere is represented by:
`E=1/(4piepsilon_0)Q/r^2`
`rArr 1.5xx10^3=9xx10^9xxQ/(0.2)^2`
`rArr Q=0.00667xx10^(-6)` C
`rArr` Q=6.67 nC