Q 15.11: A square coil of side 16cm has 200 turns and rotates in uniform magnetic field of magnitude 0.05 T. If the peak EMF is 12 V, what is the angular velocity of the cell?

Q 15.12: A generator has a rectangular coil consisting of 360 turns. The coil rotates at 420 rev per min in 0.14 T magnetic field. The peak value of EMF produced by the generator is 50 V. If the coil is 5 cm wide, find the length of the side of the coil.

Q 15.13: It is desired to make an A.C generator that can produce an EMF of 5kV with 50Hz frequency. A coil of area 1m(2) consisting of 200 turns is used as armature. What should be the magnitude of the magnetic field in which the coil rotates?

Q 15.14: The back EMF in a motor is 120 V when the motor is turning at 1680 rev/min. What is the back EMF when the motor turns at 3360 rev/min?

Q 15.15: A D.C motor operates at 240V and has a resistance of 0.5 ohm. When the motor is running at normal speed, the armature is 15A. Find the back EMF in the armature.

15.16: A copper ring has radius of 4cm and resistance of 1 milli ohm. A magnetic field applied over the ring, perpendicular to its plane. If the magnetic field increases from 0.2 T to 0.4 T in a time interval of 5 * 10(-3)s. What is the current in the ring during?

Q 15.17: A coil of 10 turns and 35 cm(2) area is in a perpendicular magnetic field of 0.5T. The coil is pulled out of the field in 1s. Find the induced EMF in the coil as it is pulled out of the field.

Q 15.18: An ideal step down transformer is connected to main supply of 240V. It is desired to operate a 12V, 30W lamp. Find the current in the primary and the transformation ratio?