When a conducting wire XY is moved towards the right, a current flows in the anti-clockwise direction. Direction of magnetic field at point O is:
1. | parallel to the motion of wire. |
2. | along with XY. |
3. | perpendicular outside the paper. |
4. | perpendicular inside the paper. |
Two coaxial coils are very close to each other and their mutual inductance is 5 mH. If a current 50 sin 500t is passed in one of the coils, then the peak value of induced e.m.f. in the secondary coil will be:
1. | 5000 V | 2. | 500 V |
3. | 150 V | 4. | 125 V |
The adjoining figure shows two different arrangements in which two square wireframes are placed in a uniform magnetic field B decreasing with time.
The direction of the induced current I in the figure is:
1. | From a to b and from c to d |
2. | From a to b and from f to e |
3. | From b to a and from d to c |
4. | From b to a and from e to f |
What is the dimensional formula of magnetic flux?
1.
2.
3.
4.
A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s, what is the change of flux linkage with the other coil?
1. 35 Wb
2. 25 Wb
3. 30 Wb
4. 20 Wb
Current in a circuit falls from \(5.0\) A to \(0\) A in \(0.1\) s. If an average emf of \(200\) V is induced, the self-inductance of the circuit is:
1. \(4\) H
2. \(2\) H
3. \(1\) H
4. \(3\) H
A \(1~\text{m}\) long metallic rod is rotating with an angular frequency of \(400~\text{rad/s}\) about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of \(0.5~\text{T}\) parallel to the axis exists everywhere. The emf induced between the center and the ring is:
1. \(200~\text{V}\)
2. \(100~\text{V}\)
3. \(50~\text{V}\)
4. \(150~\text{V}\)
A copper rod of mass m slides under gravity on two smooth parallel rails l distance apart and set at an angle to the horizontal as shown in fig. At the bottom, the rails are joined by a resistance R. There is a uniform magnetic field perpendicular to the plane of the rails. The terminal velocity of the rod is:
1.
2.
3.
4.
A 10 H inductor carries a current of 20 A. How much ice at 0°C could be melted by the energy stored in the magnetic field of the inductor?
Latent heat of ice is 2.26 × J/kg .
1. | 0.08 kg | 2. | 8.8 kg |
3. | 0.88 kg | 4. | 0.44 kg |
Some magnetic flux is changed from a coil of resistance 10 . As a result, an induced current is developed in it, which varies with time as shown in the figure. The magnitude of change in flux through the coil in Wb is:
1. | 2 | 2. | 4 |
3. | 6 | 4. | None of these |