Question

3 point charges of 1C 2C 3C are placed at the corners of an equilateral triangle of side 1m calculate the work done to move this charges to the corners of a smaller triangle of side 0.5

Answer 1

Dear Student,
 work done on the system is change in their potential energies in the two configurations.
let q1= 1C
   q2 = 2C
   q3  = 3C
​so initial potential energy of the arrangement r=1m
U = k (q1q2/r +q2q3/r + q3q1/r)                      where k is constant ( 9 * 109)
    = k(2+6+3)/1  
U initial = 11k .............  (1)
 initial potential energy of the arrangement r=0.5 m 
Ufinal = k (q1q2/r +q2q3/r + q3q1/r)
   =k(2+6+3)/0.5
  =22 k ........................ (2)

Work Done = Ufinal - U initial
                  = 22k - 11k 
                 = 11 k 
                = 11 * 9*109
                = 99 * 109  Joule    ans
 

Answer 2

Here is your answer mate... See the attachment file