The electric field and electric potential at any point due to a point charge kept in air si `20 N C^(-1)` and `10 J C^(-1)` respectively. Compute the magnitude of this charge.

Explanation

Here electric field `E = Q/(4pi epsi_0 r^2) = 20 N//C` …(i)
and electric potential `V = Q/(4pi epsi_0r) = 10 J//C` …(ii)
Dividing (ii) by (i), we get `r = 10/20 = 0.5 m`
Substituding value of r in (ii), we get
`Q = 4pi epsi_0. r xx 10 = (0.5 xx 10)/(9 xx 10^9) = 5.55 xx10^(-10) C.`