Question

Three identical charges are placed at corners of a equilateral triangel of side l. If force between any two charges is F, the work required to double the dimensiions of triangle is
A. `-3Fl`
B. `3Fl`
C. `(-3//2)Fl`
D. `(3//2)Fl`

Answer 1

Correct Answer - C
`W=/_U_i`
`=U_f-U_i`
`=3[1/(4piepsilon_0).(qq)/(2l)]-3[1/(4piepsilon_0).(qq)/l]`
`=(-3/2)(1/(4piepsilon_0).q^2/l^2)l=-3/2Fl`