Question

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

Answer 1

According to the figure given below both the charges can be located in a coordinate frame of reference.

At A, amount of charge, $q_A=2.5\times {10}^{-7}C$ (Given)

At B, amount of charge, $q_B=-2.5\times {10}^{-7}C$ (Given)

Total charge of the system,

$a=q_A+q_B=2.5\times {10}^{-7}C-2.5\times {10}^{-7}C=0$

Distance between two charges at points A and B,

$d=15+15=30cm=0.3m$

Electric dipole moment of the system is given by,

$p=q_A\times d=q_B\times d=2.5\times {10}^{-7}\times 0.3=7.5\times {10}^{-8}Cm$ along positive z-axis

Therefore, the electric dipole moment of the system is $7.5\times {10}^{-8}Cm$ along positive z−axis.