Question : Two charges of magnitude 5nC and -2nC, are placed at points (2cm, 0, 0) and (x, 0,0) in a region of space, where there is no other external field. If the electrostatic potential energy of the system is -0.5µJ, what is the value of x?
Doubt by Zoya
Solution :
q1 = 5nC = 5×10-9 C
q2 = -2nC = -2×10-9 C
r1 = 2cm = 2×10-2 m
r2 = x cm = x×10-2 m
Distance between the two charges
= r21
= r2-r1
= x×10-2 - 2×10-2
= (x-2)×10-2 m
U = -0.5µJ = -0.5×10-6 J
Electrostatic Potential Energy of a system of two point charges
Hence, the required value of x is 20 m or 2000 cm
