Q. No.A conducting square frame of side 'a' and a long straight wire carrying current i are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity v. The emf induced in the frame will be proportional to:
1. 1/x2
2. 1/(2x-a)2
3. 1/(2x+a)2
4. 1/(2x-a) x (2x+a)
1. 1/x2
2. 1/(2x-a)2
3. 1/(2x+a)2
4. 1/(2x-a) x (2x+a)
In the figure shown a square loop of side and resistance is placed near an infinitely long wire carrying a constant current . The sides and are parallel to the wire. The wire and the loop are in the same plane. The loop is rotated by about an axis parallel to the long wire and passing through the midpoints of the side and . The total amount of charge which passes through any point of the loop during rotation is:
| 1. | \(\frac{\mu _{0}Ia}{2\pi r}~ln(2)\) |
| 2. | \(\frac{\mu _{0}Ia}{\pi r}~ln(2) \) |
| 3. | \(\frac{\mu _{0}Ia^2}{2\pi r}\) |
| 4. | cannot be found because the time of rotation not given. |
The number of turns in a coil of wire of fixed radius & length is 600 and its self-inductance is 108 mH. The self-inductance of a coil of 500 turns will be:
1. 74 mH
2. 75 mH
3. 76 mH
4. 77 mH
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 |
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 |
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 conducting wire is moving towards the right in a magnetic field B. The direction of the induced current in the wire is shown in the figure. The direction of the magnetic field will be:
| 1. | In the plane of paper pointing towards the right. |
| 2. | In the plane of paper pointing towards the left. |
| 3. | Perpendicular to the plane of the paper and downwards. |
| 4. | Perpendicular to the plane of the paper and upwards. |
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