Q. No.The current sensitivity of a moving coil galvanometer is \(5~\text{div/mA}\) and its voltage sensitivity (angular deflection per unit voltage applied) is \(20~\text{div/V}.\) The resistance of the galvanometer is:
1. \(40~\Omega\)
2. \(25~\Omega\)
3. \(250~\Omega\)
4. \(500~\Omega\)
1. \(40~\Omega\)
2. \(25~\Omega\)
3. \(250~\Omega\)
4. \(500~\Omega\)
If a square loop \({ABCD}\) carrying a current \(i\) is placed near and coplanar with a long straight conductor \({XY}\) carrying a current \(I,\) what will be the net force on the loop?
1. \(\dfrac{\mu_0Ii}{2\pi}\)
2. \(\dfrac{2\mu_0IiL}{3\pi}\)
3. \(\dfrac{\mu_0IiL}{2\pi}\)
4. \(\dfrac{2\mu_0Ii}{3\pi}\)
A rectangular coil of length \(0.12~\text{m}\) and width \(0.1~\text{m}\) having \(50\) turns of wire is suspended vertically in a uniform magnetic field of strength \(0.2~\text{Wb/m}^2\). The coil carries a current of \(2~\text{A}\). If the plane of the coil is inclined at an angle of \(30^{\circ}\) with the direction of the field, the torque required to keep the coil in stable equilibrium will be:
1. \(0.15~\text{N-m}\)
2. \(0.20~\text{N-m}\)
3. \(0.24~\text{N-m}\)
4. \(0.12~\text{N-m}\)
A wire carrying current \(I\) has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to \(X\)-axis while the semicircular portion of radius \(R\) is lying in the \(Y\text-Z\) plane. The magnetic field at point \(O\) is:
1. \(B=\frac{\mu i }{4\pi R}\left ( \pi \hat{i}+2\hat{k} \right )\)
2. \(B=-\frac{\mu i }{4\pi R}\left ( \pi \hat{i}-2\hat{k} \right )\)
3. \(B=-\frac{\mu i }{4\pi R}\left ( \pi \hat{i}+2\hat{k} \right )\)
4. \(B=\frac{\mu i }{4\pi R}\left ( \pi \hat{i}-2\hat{k} \right )\)
An electron moving in a circular orbit of radius \(r\) makes \(n\) rotations per second. The magnetic field produced at the centre has a magnitude:
| 1. | \(\dfrac{\mu_0ne}{2\pi r}\) | 2. | zero |
| 3. | \(\dfrac{n^2e}{r}\) | 4. | \(\dfrac{\mu_0ne}{2r}\) |
The resistance of an ammeter is 13 Ω and its scale is graduated for a current up to 100 A. After an additional shunt has been connected to this ammeter, it becomes possible to measure currents up to 750 A by this ammeter. The value of shunt resistance is:
1. 20
2. 2
3. 0.2
4. 2 k
1. \(\frac{qvR}{2}\)
2. \(qvR^{2}\)
3. \(\frac{qvR^{2}}{2}\)
4. \(qvR\)
In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential \(V\) and then made to describe semi-circular paths of radius \(R\) using a magnetic field \(B\). If \(V\) and \(B\) are kept constant, the ratio of \(\left(\frac{\text{Charge on the ion}}{\text{Mass of the ion}} \right)\) will be proportional to:
1. \(\frac{1}{R}\)
2. \(\frac{1}{R^2}\)
3. \(R^2\)
4. \(R\)
A beam of electrons passes un-deflected through mutually perpendicular electric and magnetic fields. Where do the electrons move if the electric field is switched off and the same magnetic field is maintained?
| 1. | in an elliptical orbit. |
| 2. | in a circular orbit. |
| 3. | along a parabolic path. |
| 4. | along a straight line. |
| 1. | Angle between \(\vec v\) and \(\vec {B}\) is necessarily \(90^{\circ}\). |
| 2. | Angle between \(\vec v\) and \(\vec {B}\) can have any value other than \(90^{\circ}\). |
| 3. | Angle between \(\vec v\) and \(\vec {B}\) can have any value other than zero and \(180^{\circ}\). |
| 4. | Angle between \(\vec v\) and \(\vec {B}\) is either zero or \(180^{\circ}\). |
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