Q. No.A magnetic needle suspended parallel to a magnetic field requires \(\sqrt{3}~\text{J}\) of work to turn it through \(60^\circ\)
1. \(3\) N-m
2. \(\sqrt{3} \) N-m
3. \(\frac32\) N-m
4. \(2\sqrt{3}\) N-m
1. \(3\) N-m
2. \(\sqrt{3} \) N-m
3. \(\frac32\) N-m
4. \(2\sqrt{3}\) N-m
If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by \(\mu_d,~\mu_p,~\text{and}~\mu_f\) respectively, then:
1. \(\mu_p= 0 ~\text{and}~\mu_f \ne0\)
2. \(\mu_d\neq 0 ~\text{and}~\mu_p=0\)
3. \(\mu_d\ne 0 ~\text{and}~\mu_f \ne0\)
4. \(\mu_d= 0 ~\text{and}~\mu_p \ne0\)
Which of the following is the correct representation of magnetic field lines?
| 1. | (g), (c) | 2. | (d), (f) |
| 3. | (a), (b) | 4. | (c), (e) |
A solenoid has a core of material with relative permeability \(400.\) The windings of the solenoid are insulated from the core and carry a current of \(2~\text A.\) If the number of turns is \(1000\) per metre, the magnetic field intensity \(H\) is:
1. \(2\times10^2~\text{A/m}\)
2. \(2\times10^3~\text{A/m}\)
3. \(2~\text{A/m}\)
4. \(20~\text{A/m}\)
Figure shows two small identical magnetic dipoles \(a\) and \(b\) of magnetic moments \(M\) each, placed at a separation \(2d\), with their axes perpendicular to each other. The magnetic field at the point \(P\) midway between the dipoles is:
| 1. | \(\dfrac{2 \mu_{0} M}{4 \pi d^{3}}\) | 2. | \(\dfrac{\mu_{0} M}{4 \pi d^{3}}\) |
| 3. | zero | 4. | \(\dfrac{\sqrt{5}\mu_{0} M}{4\pi d^{3}}\) |
| 1. | increase many times | 2. | decrease many times |
| 3. | remain almost constant | 4. | become zero |
The magnetic field at the centre of a circular loop of area \(A\) is \(B.\) The magnetic moment of the loop is:
| 1. | \(\dfrac{BA^2}{\mu_0\pi}\) | 2. | \(\dfrac{BA\sqrt A}{\mu_0}\) |
| 3. | \(\dfrac{BA\sqrt A}{\mu_0\pi}\) | 4. | \(\dfrac{2BA\sqrt A}{\mu_0\sqrt\pi}\) |
A current-carrying loop placed in a magnetic field behaves like a:
1. magnetic dipole
2. magnetic substance
3. magnetic pole
4. all are true
A Rowland ring of mean radius \(15\) cm has \(3500\) turns of wire wound on a ferromagnetic core of relative permeability \(800.\) What is the magnetic field \(B\) in the core for a magnetizing current of \(1.2\) A?
1. \(3.27\) T
2. \(2.56\) T
3. \(1.05\) T
4. \(4.48\) T
A closely wound solenoid of \(800\) turns and area of cross-section \(2.5 \times10^{-4}~\text{m}^2\) carries a current of \(3.0~\text{A}\). If the solenoid acts like a bar magnet, then what is its associated magnetic moment?
1. \(0.6~\text{J/T}\)
2. \(0.07~\text{J/T}\)
3. \(0.3~\text{J/T}\)
4. \(0.8~\text{J/T}\)
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