A point charge 2 C is kept fixed at the origin Another point charge 4 C is brought from - Physics - Electrostatic Potential And Capacitance

Question

A point charge 2µC is kept fixed at the origin Another point
charge 4µC is brought from far off point to 50cm from the
origin Calculate the electrostatic potential energy of this two
charge system calculate the work done to bring another charge of
1µC is brought to a point 100cm from each of these two
charges (both the charges are assumed to be fixed)

Shobhit Mittal · Accepted Answer

Dear Student,
the potential energy of the two charge system 
U=k2410-120 5=72*10-30 5=0
144 J when the charge 1 micro coulomb put in the system the new potential energy of the system is U'=0
144+k1410-121+k1210-121=0 144+0 036+0 018=0
198 J work done =0 198-0 144=0
054 J regards