An a.c. generator consists of a coil of 50 turns and area `2.5 m^(2)` rotating at an angular speed of 60 `rad s^(-1)`, in a uniform magnetic field B = 0.30 T between two fixed pole pieces. The resistance of the circuit including that of coil is `500 Omega`.
(a) What is the max. current drawn from the generator?
(b) What is the flux through the coil when the current is zero ? What is the flux when the current is max. ?
(c ) Would the generator work if the coil were stationary and instead pole pieces rotated together with the same speed as above ?

Explanation

Here, `N = 50, A = 2.5 m^(2), omega = 60 rad//s^(-1), B = 0.30 T, R = 500 Omega`
Max. value of induced e.m.f.
`e_(0) = NAB omega :.` Max. current, `I_(0) = (e_(0))/(R ) = (NAB omega)/(R ) = (50 xx 2.5 xx 0.30 xx 60)/(500) = 4.5 amp`
(b) When current is zero, induced e.m.f = 0. As induced e.m.f. is rate of change of mag. flux, therefore, mag. flux must be maximum `= NAB = 50 xx 2.5 xx 0.3 = 37.5` weber
On the contrary, when current is maximum, induced emf is maximum. Therefore, magnetic flux linked with the coil must be zero.
(c ) Yes, the generator will work if pole pieces are rotated instead of coil. This is because only relative motion between the coil and magnet is needed.