Two coils have a mutual inductance of 0.005 H. The current changes in the first coil according to the equation I = I0 sin ωt where I0 = 10A and ω = 100π rad/sec. The maximum value of e.m.f. in the second coil is
5π volts
2π volts
π volts
4π volts
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
A circuit has a self inductance of 1 H and carries a current of 2 A. To prevent sparking when the circuit is broken, a capacitor which can withstand 400 V is used. The capacitance of the capacitor is
25 μF
125 μF
100 pF
50 μF
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
The north pole of a long horizontal bar magnet is brought closer to the vertical conducting plane along perpendicular direction. The induced current in the conducting plane is :
anticlockwise
clockwise
horizontal
vertical
The magnetic flux linked with a coil is given by the equation : Φ = 5 t2 + 3 t + 6.Find out the induced e.m.f. in 4 seconds ?
20 V
40 V
10 V
80 V
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
If a current is passed through a spring, then the spring
expands
gets compressed
remains same
None of these
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
10 s
0.01 s
1s
An aircraft has a wing span of 35 m. It is flying horizontally with a speed of 9 ms-1 and the vertical component of earth's magnetic field is 4 x 10-5T. The potential difference between the tips of the wings will be
12.6 V
0.126 V
1.26 V
0.013 V