A coil having number of turns NN and cross-sectional area AA is rotated in a uniform magnetic field BB with an angular velocity ωω. The maximum value of the emf induced in it is:
1. NBAωNBAω
2. NBAωNBAω
3. NBAω2NBAω2
4. NBAω2NBAω2
A current-carrying wire is placed below a coil in its plane, with current flowing as shown.
If the current increases –
1. no current will be induced in the coil
2. an anticlockwise current will be induced in the coil
3. a clockwise current will be induced in the coil
4. the current induced in the coil will be first anticlockwise and then clockwise
Average energy stored in a pure inductance L when a current i flows through it, is
1. Li2Li2
2. 2Li22Li2
3. Li2/4Li2/4
4. Li2/2Li2/2
A small magnet is along the axis of a coil and its distance from the coil is 80 cm. In this position the flux linked with the coil are 4 × 10–54 × 10–5 weber turns. If the coil is displaced 40 cm towards the magnet in 0.08 second, then the induced emf produced in the coil will be -
1. 0.5 mV
2. 1 mV
3. 7 mV
4. 3.5 mV
When the current in a certain inductor coil is 5.0 A and is increasing at the rate of 10.0 A/s, the potential difference across the coil is 140V. When the current is 5.0 A and decreasing at the rate of 10.0 A/s, the potential difference is 60V. The self-inductance of the coil is –
1. 2H
2. 4H
3. 8H
4. 12H
A train is moving at a rate of 72 km/hr on a horizontal plane. If the earth's horizontal component of magnetic field is 0.345 A/m and the angle of dip is 30°, then the potential difference across the two ends of a compartment of length 1.7 m will be-
1. 1.7 V1.7 V
2. 85√3×10-4 V85√3×10−4 V
3. 85×10-4 V85×10−4 V
4. 850 μ V850 μ V
The magnetic flux through a coil varies with time as ϕ= 5t2+6t+9ϕ= 5t2+6t+9. The ratio of emf at t = 3s to t = 0s will be
1. 1 : 9
2. 1 : 6
3. 6 : 1
4. 9 : 1
A wire of fixed lengths is wound on a solenoid of length l and radius r. Its self inductance is found to be L. Now if same wire is wound on a solenoid of length l/2 and radius r/2, then the self inductance will be –
1. 2L
2. L
3. 4L
4. 8L
PQ is an infinite current carrying conductor. AB and CD are smooth conducting rods on which a conductor EF moves with constant velocity v as shown. The force needed to maintain constant speed of EF is –
1. 1VR[μ0Iv2π ln (ba)]2
2. 1VR[μ0Iv2 ln (ba)]2
3. VR[μ0IV2 ln (ba)]2
4. VR[μ0IV2π ln (ba)]2
A 50 turns circular coil has a radius of 3 cms, it is kept in a magnetic field acting normal to the area of the coil. The magnetic field B increased from 0.10 tesla to 0.35 tesla in 2 milliseconds. The average induced emf in the coil is-
1. 1.77 volts
2. 17.7 volts
3. 177 volts
4. 0.177 volts