The work done to assemble the three charges in a configuration as shown in the figure below is
 

Options

A. `(-3q^(2))/(4pi epsilon_(0)a)`
B. `(-2q^(2))/(4pi epsilon_(0)a)`
C. `(-q^(2))/(4pi epsilon_(0)a)`
D. 0

Answer

C

Explanation

Work done,
`W=U_(12)+U_(23)+U_(13)`
`=(kq_(1)q_(2))/(r_(12))+(kq_(2)kq_(3))/(r_(23))+(kq_(1)q_(3))/(r_(13))`
`=(1)/(4pi epsilon_(0)a)[-2q^(2)+2q^(2)-q^(2)]`