Q. No.The number of turns in a coil of wire of fixed radius & length is 600 and its self-inductance is 108 mH. The self-inductance of a coil of 500 turns will be:
1. 74 mH
2. 75 mH
3. 76 mH
4. 77 mH
A magnetic rod is inside a coil of wire which is connected to an ammeter. If the rod is stationary, which of the following statements is true?
| 1. | The rod induces a small current. |
| 2. | The rod loses its magnetic field. |
| 3. | There is no induced current. |
| 4. | None of these. |
A coil of resistance 20 and inductance 5 H has been connected to a 200 V battery. The maximum energy stored in the coil is:
| 1. | 250 J | 2. | 125 J |
| 3. | 500 J | 4. | 100 J |
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. |
In the figure magnetic energy stored in the coil is:
| 1. | Zero | 2. | Infinite |
| 3. | 25 joules | 4. | None of the above |
Consider the situation shown in the figure. The wire AB is sliding on the fixed rails with a constant velocity. If the wire AB is replaced by semicircular wire, the magnitude of the induced current will:
| 1. | increase. |
| 2. | remain the same. |
| 3. | decrease. |
| 4. | increase or decrease depending on whether the semicircle bulges towards the resistance or away from it. |
A wire cd of length l and mass m is sliding without friction on conducting rails ax and by as shown. The vertical rails are connected to each other with a resistance R between a and b. A uniform magnetic field B is applied perpendicular to the plane abcd such that cd moves with a constant velocity of:
| 1. | \({mgR \over Bl}\) | 2. | \({mgR \over B^2l^2}\) |
| 3. | \({mgR \over B^3l^3}\) | 4. | \({mgR \over B^2l}\) |
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.
A long solenoid has 1000 turns. When a current of 4 A flows through it, the magnetic flux linked with each turn of the solenoid is 4 x 10-3 Wb. The self-inductance of the solenoid is:
1. 3 H
2. 2 H
3. 1 H
4. 4 H
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 |
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