A square of side L meters lies in the XY-plane in a region where the magnetic field is given by \(\vec{B}=B_{0}\left ( 2\hat{i} +3\hat{j}+4\hat{k}\right )~T\) where \(B_{0}\) is constant. The magnitude of flux passing through the square will be:
1.
2.
3.
4.
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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 |
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Two identical conductors P and Q are placed on two frictionless (conducting) rails R and S in a uniform magnetic field directed into the plane. If P is moved in the direction as shown in the figure with a constant speed, then rod Q:
1. | will be attracted toward P |
2. | will be repelled away from P |
3. | will remain stationary |
4. | maybe repelled or attracted towards P |
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Two coaxial coils are very close to each other and their mutual inductance is 5 mH. If a current 50 sin 500t is passed in one of the coils, then the peak value of induced e.m.f. in the secondary coil will be:
1. | 5000 V | 2. | 500 V |
3. | 150 V | 4. | 125 V |
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With the decrease of current in the primary coil from 2 A to zero in 0.01 s, the e.m.f. generated in the secondary coil is \(1000~\mathrm{V}\). The mutual inductance of the two coils is:
1. 1.25 H
2. 2.50 H
3. 5.00 H
4. 10.00 H
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A long solenoid has self-inductance L. If its length is doubled keeping total number of turns constant, then its new self-inductance will be:
1.
2. 2L
3. L
4.
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An inductor is connected to a direct voltage source through a switch. Then:
1. | a very large emf is induced in inductor when the switch is closed. |
2. | a large emf is induced when the switch is opened. |
3. | a large emf is induced whether the switch is closed or opened. |
4. | no emf is induced whether the switch is closed or opened. |
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The magnetic energy stored in a long solenoid of an area of cross-section A in a small region of length L is:
1.
2.
3.
4.
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Eddy currents are induced when:
1. A metal block is kept in a changing magnetic field.
2. A metal block is kept in a uniform magnetic field.
3. A coil is kept in a uniform magnetic field.
4. Current is passed in a coil.
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When a conducting wire XY is moved towards the right, a current flows in the anti-clockwise direction. Direction of magnetic field at point O is:
1. | parallel to the motion of wire. |
2. | along with XY. |
3. | perpendicular outside the paper. |
4. | perpendicular inside the paper. |
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