A charge 50 µc has electric field strength of 360 NC‾¹ at a certain point. The electric field strength due to another charge 120 µc kept at the same distance apart and in the same medium is?

A. 864 NC‾¹
B. 150 NC‾¹
C. 144 NC‾¹
D. 18 NC‾¹

Correct Answer: Option A
Explanation
In general, electric field strength E = (F)/q

E = q/4πε0d²
⇒ 360 = 9×10⁹×50×10^-6/d²
solving, we have d² = 1250

putting d² = 1250 into the second equation,

E = 9×10⁹×120×10^-6 /1250

we have E = 864NC‾¹