Q. No.A long solenoid carrying a current produces a magnetic field \(B\) along its axis.
If the current is doubled and the number of turns per cm is halved, what will be the new value of the magnetic field?
1. \(B/2\)
2. \(B\)
3. \(2B\)
4. \(4B\)
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 |
Magnetic field at the outer surface of long hollow cylindrical shells of radius R and carrying current I is B. What is the magnetic field at a distance of from the axis of the cylindrical shell?
| 1. | \(B \over 2\) | 2. | \(2B\) |
| 3. | \(B \over 4\) | 4. | \(2B \over 3\) |
If an i-ampere current flows through an infinitely long, straight, thin-walled tube, what will be the magnetic induction at any point within the tube?
| 1. | infinite | 2. | zero |
| 3. | \( \frac{\mu_0 2 i}{4 \pi} ~\text{T } \) | 4. | \( \frac{\mu_0 i}{2 r} ~\text{T} \) |
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. \(1:2\)
If a long hollow copper pipe carries a direct current along its length, then the magnetic field associated with the current will be:
| 1. | Only inside the pipe | 2. | Only outside the pipe |
| 3. | Both inside and outside the pipe | 4. | Zero everywhere |
What is a representation of the magnetic field caused by a straight conductor with a uniform cross-section and a steady current of radius 'a'?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
A long solenoid has 800 turns per metre of the length of the solenoid. A current of 1.6 A flows through it. What is the magnetic induction at the end of the solenoid on its axis?
| 1. | \(16 \times 10^{-4}~\mathrm T\) | 2. | \(8 \times 10^{-4}~\mathrm T\) |
| 3. | \(32 \times 10^{-4}~\mathrm T\) | 4. | \(4 \times 10^{-4}~\mathrm T\) |
A long straight wire of radius 'a' carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B' at radial distances a/2 and 2a respectively, from the axis of the wire, is:
| 1. | 1/2 | 2. | 1 |
| 3. | 4 | 4. | 1/4 |
Consider six wires with the same current flowing through them as they enter or exit the page. Rank the magnetic field's line integral counterclockwise around each loop, going from most positive to most negative.
1. B > C > D > A
2. B > C = D > A
3. B > A > C = D
4. C > B = D > A
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