Two point charges `4mu C and 9muC` are separated by 30cm. Find the point where the strength of the field is zero.

Explanation

The distance x of the null point `4mu C` charge and between the two charge is
`(4)/(x^(2)) = (9)/((30-x)^(2)) (or) x = (30)/(sqrt((9)/(4))+1)= (30 xx 2)/(5) = 12cm`