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. \(0.13~\mathrm{V}\)
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
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. |
A conducting circular loop is placed in a uniform magnetic field of 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at a rate of 2 mm/s. The induced e.m.f. in the loop when the radius is 2 cm is:
1. \(3.2\pi ~\mu V\)
2. \(4.8\pi ~\mu V\)
3. \(0.8\pi ~\mu V\)
4. \(1.6\pi ~\mu V\)
A magnet is brought towards a coil first (i) speedily (ii) slowly. It can be concluded that the induced e.m.f. and the induced charge in the two cases, will be respectively:
1. | More in the first case, more in the first case. |
2. | More in the first case, equal in both cases. |
3. | Less in the first case, more in the second case. |
4. | Less in the first case, equal in both cases. |