A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is:
1. | Twice per revolution | 2. | Four times per revolution |
3. | Six times per revolution | 4. | Once per revolution |
The current I in an inductance coil varies with time t according to the graph shown in the figure. Which one of the following plots shows the variation of voltage in the coil with time?
1. | 2. | ||
3. | 4. |
A bar magnet is released along the vertical axis of the conducting coil. The acceleration of the bar magnet is:
1. | greater than g. | 2. | less than g. |
3. | equal to g. | 4. | zero. |
A rod having length l and resistance R0 is moving with speed v as shown in the figure. The current through the rod is:
1.
2.
3.
4.
A solenoid of inductance L and resistance R is connected to a battery of e.m.f. E. Maximum value of magnetic energy stored in the inductor is:
The coefficient of mutual inductance between two coils depends upon:
1. | medium between coils |
2. | separation between coils |
3. | orientation of coils |
4. | All of these |
A small square loop of wire of side 'l' is placed inside a large square loop of side 'L' (Ll). If the loops are coplanar and their centres coincide, the mutual inductance of the system is directly proportional to:
1. L/l
2. l/L
3. L2/l
4. l2/L
Two coils have a mutual inductance of 5 mH. The current changes in the first coil according to the equation \(I=I_{0}cos\omega t,\) where \(I_{0}=10~A\) and = 100 rad/s. The maximum value of e.m.f. induced in the second coil is:
1. 5 Volt
2. 2 Volt
3. 4 Volt
4. Volt
Eddy currents are used in:
1. Induction furnace
2. Electromagnetic brakes
3. Speedometers
4. All of these
The magnetic flux linked with a coil varies with time as \(\phi = 2t^2-6t+5,\) where \(\phi \) is in Weber and \(t\) is in seconds. The induced current is zero at:
1. \(t=0\)
2. \(t= 1.5~\text{s}\)
3. \(t=3~\text{s}\)
4. \(t=5~\text{s}\)