A plastic rod has been formed into a circle of radius R. It has a positive charge `+Q` uniformly distributed along one-quarter of its circumference and a negative charge of ` -6Q` uniformly distributed along the rest of the circumference (figure). With V = 0 at infinity, what is the electric potential `-6Q`
(a) at the centre C of the circle and
(b) at point P, which is on the central axis of the circle at distance z from the centre?

Answer

D

Explanation

`a. V_C=(k.q_("net"))/R=(1/(4piepsilon_0)((-5Q)/R)`
`b. V_p=(kq_("net"))/r` where r=distance of P from any point on circumfrence
`=(1/(4piepsilon_0))((-5Q)/(sqrt(R^2+z^2)))`