In a current carrying coil the enery is stored as which of the following form ?
Electric field
Magnetic field
Dielectric strength
Heat
The magnetic energy in an inductor changes from maximum value to minimum value in 5 ms when connected to an a.c. source. The frequency of the source is
50 Hz
200 Hz
500 Hz
20 Hz
Two circuits have mutual inductance of 0.09 H. Average e.m.f. induced in the secondary by a change of current from 0 to 20 A in 0.006 second in the primary will be
300 V
200 V
180 V
120 V
A 100 mH coil carries a current of 1 A. Energy stored in the magnetic field is
0.5 J
1 J
0.1 J
0.05 J
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
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
A rectangular coil of 20 turns and area of cross-section 25 cm2 has a resistance of 100 Ω. If a magnetic field which is perpendicular to the plane of the coil changes at the rate of 1000 T per second, the current in the coil is
1A
50 A
0. 5 A
5 A
A current carrying solenoid contains an iron rod inside it. A current flows in the solenoid due to a DC source, of constant emf, connected across the ends of the solenoid. When the rod is pulled out of the solenoid, then the current in the solenoid will
Increase
Decrease
Remain constant
Becomes zero
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
A coil of 1000 turns of wire is wound on a book and this book is lying on the table. The vertical component of earth's magnetic field is 0.6 x 10-4 T and the area of the coil is 0.05m2. The book is turned through 180o about a horizontal axis in 0.1 second. The average e.m.f. induced in the coil is
0.03 V
0.06 V
zero
0.6 V
