Two similarly and equally charged identical metal spheres A and B repel each other with a force of `2xx10^(-5)N`. A third identical uncharged sphere C is touched with A and then placed at the midpoint between A and B. Find the net electric force on C.

Answer

`2xx10^(-5)`, towards A

Explanation

In fig

`F = 2xx10^(-5) = (qq)/(4pi in_(0) r^(2))`
On touching C and A, charge on each `= q//2` Net force on C
`F' = F_(2) - F_(1)`
`F' = (q(q//2))/(4pi in_(0) (r//2)^(2)) - ((q//2) (q//2))/(4pi in_(0) (r//2)^(2))`
`= (q^(2))/(4pi in_(0)) [(2)/(r^(2)) - (1)/(r^(2))] = (q^(2))/(4pi in_(0) r^(2))`
`F' = F = 2xx10^(-5)`, towards A