Q.

A coil of area A and N turns is rotating with angular velocity ω in a uniform magnetic field B about an axis perpendicular to B. Magnetic flux φ and induced emf ε across it, at an instant when B is parallel to the plane of coil, are:          [2025]

1 φ=AB, ε=0  
2 φ=0, ε=NABω  
3 φ=0, ε=0  
4 φ=AB, ε=NABω  

Ans.

(2)

ϕ=NBA cos θ

ε=dϕdt=NBAd(cos θ)dt

θ=ωt

ε=NBA ω sin ωt

if B is parallel to plane of coil

ω=90°

ϕ=0, E=BAωN