A charge 'Q' is divided into two parts A and B the two parts are separated by a certain fixed distance. Find for what charges on A and B would the force between them be maximum and comment when the force is minimum.

Explanation

(i) `F = (1)/(4piin_(0)) (Q_(1)Q_(2))/(d^(2))`
Then, `(1)/(4piin_(0)) (1)/(d^(2))` are constant.
`rArr F prop Q_(1).Q_(2)`
Here take `Q_(1) = Q/n` then `Q_(2) = (Q - Q/n)`
`= ((n-1)/(n)) Q`
`rArr F prop (Q)/(n) ((n-1)Q)/(n) = ((n-1)Q^(2))/(n^(2))`
F is maximum, when n is minimum
F is minimum, when n is maximum
(ii) `W//2,Q//12`.