Question

A system has two charges q_A = 2.5× 10^-7C and q_B = -2.5 x 10^-7C located at points A: (0, 0, -15cm), respectively. What are the total charge and electric dipole moment of the system?

Answer 1

The charges q_A and q_B are located at the points A (0,0, – 15cm)

and B (0, 0, +15cm). B The points A and B lie on z-axis as shown. It follows that, 

AB = OA + OB = 30cm = 0.3m

Total charge, q = q_A + q_B

= 2.5 x 10^-7 + (-2.5 x 10^-7)

= 0

Electric dipole moment,

p = either charge x AB

= 2.5 x 10^-7 x 0.3

= 7.5 x 10^-8 m

The electric dipole moment is directed from B to A along z-axis.