A coil has an area of 0.05 m2 and has 800 turns. After placing the coil in a magnetic field of strength 4 x 10-5 Wbm-2, perpendicular to the field, the coil is rotated by 90o in 0.1s.The average emf induced is :
zero
0.016 V
0.01 V
0.032 V
The number of turns in a secondary coil is twice the number of turns in primary. A Leclanche cell of 1.5 V is connected across the primary. The voltage acrosss secondray is
1.5 V
3 V
240 V
A coil is wound in a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor of 3 and the number of turns per unit length remains the same, the self inductance increases by a factor of :
3
9
27
8
Two rails of a railway track insulated from each other and the ground are connected to a millivoltmeter. What is the reading of millivoltmeter when a train travels at a speed of 180 km/hr? Given that the vertical component of earth's magnetic field is 0.2 x 10-4 Wb/m2 and the rails are separated by 1m.
10-2mV
10 mV
100 mV
1 mV
If a current is passed through a spring, then the spring
expands
gets compressed
remains same
None of these
A coil of area 100 cm2 has 500 turns. Magnetic field of 0.1 Wb/m2 is perpendicular to the coil. The field is reduced to zero in 0.1s. The induced e.m.f. in the coil is
5 V
1 V
50 V
A magnetic field of 2 x 10-2 T acts at right angles to a coil of area 100 cm2 with 50 turns. The average e.m.f. induced in the coil is 0.1 V when it is removed from the field in t sec. The value of t is
0.1 s
0.01 s
A long solenoid has 200 turns/cm and carries a current I. The magnetic field at its centre is 5.28 x 10-2 Wbm-2. Another long solenoid has 100 turns/cm and it carries a current I/3. The value of the magnetic field at its centre is
1.05 x 10-2 Wb m-2
1.05 x 10-5 Wb m-2
1.05 x 10-3 Wb m-2
1.05 x 10-4 Wb m-2
A horizontal straight wire, 10m long, extending along the east and west direction, is falling at right angles to the horizontal component of the earth's magnetic field, 0.30 x 10-4 Wbm-2. If the induced emf is 1.5 x 10-3, the velocity of the wire is :
5 x10-4 ms-1
5 x 102 ms-1
50 ms-1
5 ms-1
A coil of resistance R and inductance L is connected to a battery of e.m.f. E volts. The final current in the coil is
