Charge is uniformly distributed around a ring of radius r = 7.40 cm, and the resulting electric field magnitude e is measured along the ring's central axis (perpendicular to the plane of the ring). at what distance from the ring's center is e maximum?

Explanation:

Here if the radius of the ring is R then electric field on its axis is given by the formula

now we know that if the electric field is maximum at a point on its axis then its differentiation with respect to the distance will be zero

so we have

so we have

so here we have

R = 7.40 cm

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