Two straight horizontal parallel wires carry the same current in the same direction, and d is the distance between them. You are given a small magnetic needle that is freely suspended. Which of the following positions will have the needle's orientation independent of the magnitude of the current in the wires?
1. | At a distance d/2 from any of the wires in any plane. |
2. | At a distance d/3 from any of the wires in the horizontal plane. |
3. | Anywhere on the circumference of a vertical circle of radius d and centre halfway between the wires. |
4. | At points halfway between the wires in the horizontal plane. |
In the figure shown below there are two semicircles of radius r1 and r2 in which a current i is flowing. The magnetic induction at the centre of O will be:
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2.
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In a current-carrying long solenoid, the field produced does not depend upon:
1. | Number of turns per unit length | 2. | Current flowing |
3. | Radius of the solenoid | 4. | All of the above |
Which one of the following gives the value of the magnetic field according to Biot-Savart’s law?
1. | \(\frac{{i} \Delta {l} \sin (\theta)}{{r}^2} \) | 2. | \(\frac{\mu_0}{4 \pi} \frac{i \Delta {l} \sin (\theta)}{r} \) |
3. | \(\frac{\mu_0}{4 \pi} \frac{{i} \Delta{l} \sin (\theta)}{{r}^2} \) | 4. | \(\frac{\mu_0}{4 \pi} {i} \Delta {l} \sin (\theta)\) |
What is the magnetic field at point O in the figure?
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2.
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4.
If the current is flowing in the south direction along a power line, then what will be the direction of the magnetic field above the power line (neglecting the earth's field)?
1. | South | 2. | East |
3. | North | 4. | West |
If a wire in the form of a square with a side ‘a’ carries a current i, then the magnetic induction at the centre of the square wire will be:
(Magnetic permeability of free space = )
1. | \(\frac{\mu _{0}i}{2\pi a}\) | 2. | \(\frac{\mu _{0}i\sqrt2}{\pi a}\) |
3. | \(\frac{2\sqrt2\mu _{0}i}{\pi a}\) | 4. | \(\frac{\mu _{0}i}{\sqrt2\pi a}\) |
A proton and an α- particle enter a uniform magnetic field perpendicularly at the same speed. If a proton takes 25 μs to make 5 revolutions, then the periodic time for the α-particle will be:
1. 50 s
2. 25 s
3. 10 s
4. 5 s
Which among the following options needs to be decreased to increase the sensitivity of a moving coil galvanometer?
1. | the number of turns in the coil. | 2. | the area of the coil. |
3. | the magnetic field. | 4. | the couple per unit twist of the suspension. |
In a hydrogen atom, the electron makes 6.6×1015 rev/sec around the nucleus in an orbit of radius 0.528 Å. What will (A-m2) its magnetic moment be?
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