Two positive charges of 12 µC and 8 µC respectively are 10 cm apart. Find the work done in bringing them 4 cm closer, so that, they are 6 cm apart..

Answer 1

find the difference in PE in the two locations.

Hold one charge stationary.
PEtotal= kQQ/.1

PE(new total)=KQQ/.06

subtract the first from the second, that must equal the work done.

There are more difficult ways to work this, involving finding work in an integral calculus equation (work= INT force*dr)

Answer 2

5.8 j

Answer 3

4.8J