Two co-axisal rings, each of radius R, are separated by a small distance l(ltltR) and carry charges q and -q.Find the electric potential and field at a point on the axis at a distance x from the midpoint between the rings,

Answer

`varphi=(q//x)/(4piepsilon_(0)(R^(2)+x^(2))^(3//2)),E=(ql(R^(2)-2x^(2)))/(4piepsilon_(0)(R^(2)+x^(2))^(5//2))`