Question

Please explain. Question no. 8

Answer 1

Answer:

There are eight comers of a cube and in each corner there is a charge of (-q). At the centre of the comer there is a charge of (+q). Each corner is equidistant from the centres of the cube and the distance (d) is half of the diagonals of the cube.

the diagonal of cube

√(b²+b²+b²)

√3b

d = √3b/2

Now, electric potential energy of the charge (+q) due to a charge (-q) at one corner = u

Total electric potential energy due to all the eight

8u

- 8q²/2π€√3b

-4q²/√3π€b

options c is correct