Q. No.Lenz's law is a consequence of the law of conservation of
(1) Charge
(2) Momentum
(3) Mass
(4) Energy
A copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet while it is passing through the ring is
(1) Equal to that due to gravity
(2) Less than that due to gravity
(3) More than that due to gravity
(4) Depends on the diameter of the ring and the length of the magnet
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. |
As shown in the figure, a magnet is moved at a fast speed towards a coil at rest. Due to this induced electromotive force, induced current and induced charge in the coil is \(E\), \(I\), and \(Q\) respectively. If the speed of the magnet is doubled, the incorrect statement is:
| 1. | \(E\) increases |
| 2. | \(I\) increases |
| 3. | \(Q\) remains the same |
| 4. | \(Q\) increases |
The magnetic field in a coil of 100 turns and 40 square cm area is increased from 1 Tesla to 6 Tesla in 2 second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it is
(1) 104 V
(2) 1.2 V
(3) 1.0 V
(4) 10–2 V
A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in the horizontal direction so that the pendulum now swings through the field, the pendulum will:
| 1. | Keep oscillating with the old-time period. |
| 2. | Keep oscillating with a smaller time period. |
| 3. | Keep oscillating with a larger time period. |
| 4. | Come to rest very soon. |
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 coil having n turns and resistance R Ω is connected with a galvanometer of resistance 4R Ω. This combination is moved in time t seconds from a magnetic field W1 to W2 . If area of each turn is 1 m2 , the induced current in the circuit is-
(1)
(2)
(3)
(4)
A rectangular coil ABCD is rotated anticlockwise with a uniform angular velocity about the axis shown in the diagram below. The axis of rotation of the coil as well as the magnetic field B are horizontal. The induced e.m.f. in the coil would be maximum when
(1) The plane of the coil is horizontal
(2) The plane of the coil makes an angle of 45° with the magnetic field
(3) The plane of the coil is at right angles to the magnetic field
(4) The plane of the coil makes an angle of 30° with the magnetic field
Two rails of a railway track insulated from each other and the ground are connected to a milli voltmeter. What is the reading of voltmeter, when a train travels with a speed of 180 km/hr along the track. Given that the vertical component of earth's magnetic field is 0.2 × 10–4 weber/m2 and the rails are separated by 1 metre
(1) 10–2 volt
(2) 10–4 volt
(3) 10–3 volt
(4) 1 volt
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