Question

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

Answer 1

Charge on A, $q_A=2.5\times {10}^{-7}C$

Charge on B, $q_B=2.5\times {10}^{-7}C$

Therefore, total charge q will be

$q=q_A+q_B$

$=2.5\times {10}^{-7}+2.5\times {10}^{-7}$

$=5\times {10}^{-7}C$

Distance between two charges, $a=15-(-15)=30cm=0.3m$

Electron dipole moment,

$p=q.a$

$=2.5\times {10}^{-7}\times 0.3$

$=7.5\times {10}^{-7}Cm$ (along z-axis)

Because the direction of dipole is always negative to positive.