Four charges `q_1=1muC, q_2=2muC, q_3=-3muC` and `q_4=4muC` are kept on the vertices of a square of side `1m`. Find the electric potential energy of this system of charges.

Options

A. `-5.28xx10^-2J`
B. `-7.62xx10^-2J`
C. `-8.91xx10^-2J`
D. `-4.33xx10^-2J`

Answer

B

Explanation

In this problem
`r_41=r_43=r_32-r_21=1m`
and `r_42=r_31=sqrt((1)^2+(1)^2) =sqrt2m`
substituting the proper values with sign in eqn ii we get
`U=(9.0xx10^9)(10^-6)(10^-6)[((4)(-3))/1+((4)(2))/sqrt2+((4)(2))/(1)+((-3)(2))/1+((-3)(1))/sqrt2+((2)(1))/1]`
`=(9.0xx10^-3)[-12+5/sqrt2]`
`=-7.62xx10^-2J`