Eddy currents are used in:
1. Induction furnace
2. Electromagnetic brakes
3. Speedometers
4. All of these
A square loop of sides 4 cm having a resistance of 2 is placed normal to a magnetic field. If the magnetic field is gradually reduced at the rate of 0.02 T/s. The induced current in the loop is
1. 8
2. 2
3. 16
4. 6
The direction of the runway on the airport should be
1. Along N-A
2. Along E-W
3. Along NW-SE
4. Along NE-SW
A metallic wheel (of radius l and 8 spokes) is rotated in a uniform magnetic field B as shown. The motional EMF across centre and rim is given by
1.
2.
3.
4.
Charged pollen grains are lying on a frictionless table. These are now subject to a certain field and are found to be moving by these fields. The field cannot be
1. Time-dependent electric field
2. Position dependent electric field
3. Time-dependent magnetic field
4. Position dependent magnetic field
The magnetic field in the region is decreasing in such a way that dB/dt = . If resistance per unit length of the loop shown is , then, the current flowing in the loop is given by
1. Clockwise
2. Anticlockwise
3. Clockwise
4. Anticlockwise
Two inductor coils of self-inductance L1 = 10 H and L2 = 20 H are placed as shown in the figure. The mutual inductance of the coil is 3H. The equivalent inductance between AB of the system of coils is
1. 36 H
2. 24 H
3.
4.
There is a solenoid of length 1.5 m having 1000 turns per metre, kept in a region where the magnetic field is increased with time as 0.2 T s-1. (radius of the solenoid is ). The current through resistance 10 is
1. 30 A
2. 3 A
3. 0.3 A
4. 0.03 A
A one-metre long metallic rod is rotated with an angular frequency of 400 radians/sec about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant uniform magnetic field of 0.5 tesla parallel to the axis exists everywhere. The emf developed between the centre and the ring is
1. 200 V
2. 100 V
3. 50 V
4. 1000 V
Self-inductances of primary and secondary of an ideal transformer are 90 mH and 40 mH. If the current in the primary decreases at the rate 103 As-1, then emf across the secondary is
1. 40 V
2. 90 V
3. 60 V
4. 20 V