- 1(current)
Q. No.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. \(t=5~\text{s}\)
A coil having number of turns N and cross-sectional area A is rotated in a uniform magnetic field B with an angular velocity . The maximum value of the emf induced in it is:
1.
2.
3.
4.
The current in a coil varies with time t as . If the inductance of coil be 10 mH, the value of induced e.m.f. at \(t=2~\mathrm{s}\) will be:
1. \(0.14~\mathrm{V}\)
2. \(0.12~\mathrm{V}\)
3. \(0.11~\mathrm{V}\)
4. \(0.13~\mathrm{V}\)
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 coil having an area is placed in a magnetic field which changes from in time interval t. The average EMF induced in the coil will be:
1.
2.
3.
4.
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 |
An aluminium ring B faces an electromagnet A. If the current I through A can be altered, then:
| 1. | whether I increases or decreases, B will not experience any force. |
| 2. | if I decreases, A will repel B. |
| 3. | if I increases, A will attract B. |
| 4. | if I increases, A will repel B. |
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 |
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 |
A metallic ring is attached to the wall of a room. When the north pole of a magnet is brought near to it, the induced current in the ring will be:
| 1. | first clockwise and then anticlockwise. |
| 2. | in the clockwise direction. |
| 3. | in the anticlockwise direction. |
| 4. | first anticlockwise and then clockwise. |
- 1(current)
Q. No.
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