Question

23. Two identical small spheres carry charge of Q, and Q2 with Qı>>Q2. The charges are d distance
apart. The force they exert on one another is F. The spheres are made to touch one another and
then separated to distance d apart. The force they exert on one another now is F2.They F/F, is:-
1) 4Q,/Q2
2) Q1/4Q2
3) 4Q2/Q1 4) Q2/4Q1​

Answer 1

So,,

F = kQ₁Q₂/d² ......            where  k = 1/4πε₀

now IN CASE 2 .... the total charge will redistribute among them...

therefore.....NEW charge on spheres :

     q = (Q₁ + Q₂)/2

now since Q₁>>>Q2

NEGLECTING Q₂....

 we get ........q= Q₁/2

F₂ = K (Q₁/2)²/d²

DIVIDING F₁/F₂

F/F₁ = 4Q₂/Q₁