Please explain 2 We have four identical conducting A and D s

2. We have four identical conducting A, and D. starts with a charge of while B contains a charge of +2Q, C a charge of -2Q, and D initially carry no net charge. Now let A and B touch and then separate. Then A touch C and separate. Finally, A touch D and then separate. Find the final charge of A.

Solution

Here,

as the charge will get equally distributed when spheres are touched

hence ,

when A and B are touched

qA = qB = (4Q + 2Q)/(2) = 3 Q

now , when A and C is touched

qA = qC = (3Q - 2Q)/(2)

qA = qC = Q/2

Now , when A and D are touched

qA = qD = (Q/2 + 0)/2

qA = qD = Q/4

hence , the final charge on A is Q/4