Q. No.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 \(\omega\). The maximum value of the emf induced in it is:
1. \(\frac{NBA}{\omega}\)
2. \(NBAω\)
3. \(\frac{NBA}{\omega^{2}}\)
4. \(NBAω^{2}\)
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 |
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. |  |
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