in these 2 qs 1)2 charges of value 2C and -50C are placed 80cm apart from each other .calculate the distance of the point from the smaller charge where the intensity is zero.
2)2 charges 4Cand 36C are placed 60cm apart from each other .calculate the distance of the point from the larger charge where the intensity is zero.
now how to locate the point i mean i q1 the point is 80+r i.e. away from the line joining the charges but in q2 it is 60-r so on what basis is this distance located can u explain

Dear student,

In the first case, the charges are of opposite sign. Hence a third charge placed between them would experience force from both of them in same direction and hence it can never be zero. Hence the point of zero intensity will lie not in between them, but outside them along the line joining them. So if the distance of it from one of them is r, then from other it will be 80+r.

But in the second case, similar charges will both repel/attract a charge kept in between them and so the forces will exactly cancel each other at some point. Hence if distance of the point from one is r, from the other it will be 60-r.