Electromagnetic Induction

Two coils, X and Y, are placed facing one another a few centimeters apart. When the current in Coil X is increased at a steady rate of 5.0 As^-1, a constant e.m.f. of 35.0 mV is induced across the terminals of Coil Y. The mutual inductance of this arrangement is

• 0.0007 H

• 0.012 H

• 0.025 H

• 0.037 H

A solenoid with a length of 20.0 cm has a total of 1260 turns of wire. If its cross-sectional area is 12.0 cm² , the inductance of solenoid is

• 12.0 mH

• 14.0 mH

• 16.0 mH

• 18.0 mH

When power is supplied to an electric motor, the motor armature rotates in a magnetic field and induced e.m.f. is generated. Which statement about the motor is not true ?

• The induced e.m.f. opposes the e.m.f. supplied

• The induced e.m.f. is greater than the e.m.f. supplied.

• The induced e.m.f. is maximum when the armature rotates with maximum speed.

• The difference voltage across the armature is smaller then the e.m.f. supplied

A small coil with 100 turns of cross-sectional area 1.26 x 10^-3 m² is placed coaxially at the centre of a solenoid with 3000 turns and length 2.44 m. What is the mutual inductance between the solenoid and the coil ?

• 6.49 x 10^-6 H

• 9.73 x 10^-5 H

• 1.95 x 10^-4 H

• 5.84 x 10^-3 H

A conducting rod being pulled from rest to move with constant acceleration in a uniform magnetic field on two horizontal tracks of negligible resistance is shown in the diagram below.

The tracks are connected to a resistor R at both of its ends. Which graph shows the variation of the induced current I with time t for the conducting rod ?

• 
• 
• 
• 

A circular conducting loop is connected to a battery and a switch S as shown in the diagram.

Immediately after S is closed, the current through the loop changes at a rate of 15.0 As^-1,and the e.m.f. induced in the loop has a magnitude of 5.0 V. What is the self - inductance of the loop ?

• 3.0 H

• 5.8 x 10^-1 H

• 3.3 x 10^-1 H

• 4.4 x 10^-2 H

A straight conductor of length 1.20 m is moving in magnetic field of 2.50 T with constant velocity. Assume that  $R=6.0\Omega$   and that the uniform magnetic field is directed into the page. At what speed should the conductor be moving to produce a current of 0.500 A in the resistor ?

•  $1.0\ ms^{-1}$  

•  $2.0\ ms^{-1}$  

•  $3.0\ ms^{-1}$  

•  $4.0\ ms^{-1}$  

Back e.m.f. is induced in a spinning electric motor. Which statement about the back e.m.f is NOT true ?

• It reduces the electric power supplied to the motor.

• Its magnitude is bigger when the motor starts to spin.

• Its direction is opposite to the direction of the voltage supplied

• It is generated when an armature coil undergoes a magnetic flux change.

A metal conductor of length 20.0 cm which is being moved with a constant velocity of $5.0ms^{-1}$     by a constant force F in a uniform magnetic field of 4.0 T is shown in the diagram below.
The ends of the conducting track which has negligible resistance is connected to a resistor  $5.0\Omega$  . What is the magnitude of force F ?

• 3.20 N

• 0.80 N

• 0.64 N

• 0.16 N

The figure below shows the side view of a circular coil of N turns and area A in a magnetic field B.
If the normal to the plane of the coil makes an angle  $\alpha$  with the magnetic field, the magnetic flux through the coil is

•  $NBA\cos\alpha$  

•  $NBA\sin\alpha$  

•  $BA\cos\alpha$  

•  $BA\sin\alpha$