Q. No.A circular coil of \(30\) turns and a radius of \(8.0 ~\text{cm}\) carrying a current of \(6.0 ~\text{A}\) is suspended vertically in a uniform horizontal magnetic field of magnitude \(1.0 ~\text{T}.\) The field lines make an angle of \(60^\circ\) with the normal of the coil. What will be the magnitude of the counter-torque that must be applied to prevent the coil from turning?
1. \(7.12 ~\text{N-m}\)
2. \(3.13~\text{N-m}\)
3. \(6.50~\text{N-m}\)
4. \(4.44~\text{N-m}\)
1. \(7.12 ~\text{N-m}\)
2. \(3.13~\text{N-m}\)
3. \(6.50~\text{N-m}\)
4. \(4.44~\text{N-m}\)
Two long and parallel straight wires \(A\) and \(B\) carrying currents of \(8.0~\text{A}\) and \(5.0~\text{A}\) in the same direction are separated by a distance of \(4.0~\text{cm}.\) The force on a \(10\) cm section of wire A is:
| 1. | \(3\times10^{-5}~\text{N}\) | 2. | \(2\times10^{-5}~\text{N}\) |
| 3. | \(3\times10^{-4}~\text{N}\) | 4. | \(2\times10^{-4}~\text{N}\) |
An ammeter reads up to \(1\) A. Its internal resistance is \(0.81\) \(\Omega\). To increase the range to \(10\) A, the value of the required shunt is:
1. \(0.09~\Omega\)
2. \(0.03~\Omega\)
3. \(0.3~\Omega\)
4. \(0.9~\Omega\)
1. \( \dfrac{{IL}^2}{4} ~\text{A}\text-\text{m}^2 \)
2. \( \dfrac{{I} \times \pi {L}^2}{4} ~\text{A}\text-\text{m}^2 \)
3. \( \dfrac{2 {IL}^2}{\pi}~\text{A}\text-\text{m}^2 \)
4. \( \dfrac{{IL}^2}{4 \pi}~\text{A}\text-\text{m}^2 \)
A long straight wire of radius \(R\) carries a uniformly distributed current \(i.\) The variation of magnetic field \(B\) from the axis of the wire is correctly presented by the graph?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
An electron enters a chamber in which a uniform magnetic field is present as shown.
An electric field of appropriate magnitude is also applied so that the electron travels undeviated without any change in its speed through the chamber. We are ignoring gravity. Then, the direction of the electric field is:
| 1. | opposite to the direction of the magnetic field. |
| 2. | opposite to the direction of the electron's motion. |
| 3. | normal to the plane of the paper and coming out of the plane of the paper. |
| 4. | normal to the plane of the paper and into the plane of the paper. |
Two toroids \(1\) and \(2\) have total no. of turns \(200\) and \(100\) respectively with average radii \(40~\text{cm}\) and \(20~\text{cm}\) respectively. If they carry the same current \(i,\) what will be the ratio of the magnetic fields along the two loops?
1. \(1:1\)
2. \(4:1\)
3. \(2:1\)
4. \(1:2\)
A thick current-carrying cable of radius '\(R\)' carries current \('I'\) uniformly distributed across its cross-section. The variation of magnetic field \(B(r)\) due to the cable with the distance '\(r\)' from the axis of the cable is represented by:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
An infinitely long straight conductor carries a current of \(5~\text{A}\) as shown. An electron is moving with a speed of \(10^5~\text{m/s}\) parallel to the conductor. The perpendicular distance between the electron and the conductor is \(20~\text{cm}\) at an instant. Calculate the magnitude of the force experienced by the electron at that instant.
1. \(4\pi\times 10^{-20}~\text{N}\)
2. \(8\times 10^{-20}~\text{N}\)
3. \(4\times 10^{-20}~\text{N}\)
4. \(8\pi\times 10^{-20}~\text{N}\)
A uniform conducting wire of length \(12a\) and resistance '\(R\)' is wound up as a current-carrying coil in the shape of;
| (i) | an equilateral triangle of side '\(a\)' |
| (ii) | a square of side '\(a\)' |
The magnetic dipole moments of the coil in each case respectively are:
1. \(3Ia^2~\text{and}~4Ia^2\)
2. \(4Ia^2~\text{and}~3Ia^2\)
3. \(\sqrt{3}Ia^2~\text{and}~3Ia^2\)
4. \(3Ia^2~\text{and}~Ia^2\)
© 2025 GoodEd Technologies Pvt. Ltd.