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

Explanation

`E=1.5xx10^(3)N//C, r=20 cm =20 xx10^(-2) m`
`E=1/(4pi epsi_(0)) q/r^(2)`
`1.5xx10^(3)=(9xx10^(9)xxq)((20xx10^(-2))^(2))`
`q=(1.5xx10^(3)xx20xx20xx10^(-4))/(9xx10^(9))=6.67xx10^(-9)C`.
As the electric field is radially inwards which shows that the nature of unknown charge q is negative.