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.
In a circuit with a coil of resistance 2 ohms, the magnetic flux changes from 2.0 Wb to 10.0 Wb in 0.2 second. The charge that flows in the coil during this time is:
1. 5.0 coulomb
2. 4.0 coulomb
3. 1.0 coulomb
4. 0.8 coulomb
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 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 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 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 |
| Assertion (A): | The bar magnet falling vertically along the axis of the horizontal coil will be having acceleration less than \(g.\) |
| Reason (R): | Clockwise current induced in the coil. |
In the light of the above statements choose the correct answer from the options given below:
| 1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 3. | (A) is true but (R) is false. |
| 4. | Both (A) and (R) are false. |
1. \(5\) V
2. \(4\) V
3. \(3\) V
4. zero
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. |
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