A metallic ring is rotating with uniform angular velocity about its diameter in a uniform magnetic field. Then emf induced in the ring is

At any time to, ϕ=A→.B→=ABcosθ=ABcosωtInduced emf, ε=−dϕdt=AωB.sinωt=AωBsinθEvidently, ε is maximum when θ=90o.and ε=0 when θ=0o.Here A→=Area vector which is perpendicular to the plane of the coil.