A circular metal of area 0.03 m2 rotates in a uniform magnetic field of 0.4 T. The axis of rotation passes through the centre and perpendicular to its plane and is also parallel to the field. If the disc completes 20 revolutions in one second and the resistance of the disc is 4 Ω, calculate the induced emf between the axis and the rim and induced current flowing in the disc.
A = 0.03 m2; B = 0.4 T; f = 20 rps; R = 4 Ω
A rectangular coil of area 70 cm2 having 600 turns rotates about an axis perpendicular to a magnetic field of 0.4 Wb m-2. If the coil completes 500 revolutions in a minute, calculate the instantaneous emf when the plane of the coil is (i) perpendicular to the field (ii) parallel to the field and (iii) inclined at 60o with the field.
A = 70 ´ 10-4m2; N = 600 turns
B = 0.4 Wbm-2; f = 500 rpm