- 1(current)
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, then the new value of the magnetic field will be equal to:
1. \(B\)
2. \(2B\)
3. \(4B\)
4. \(\dfrac B 2\)
1. \(B\)
2. \(2B\)
3. \(4B\)
4. \(\dfrac B 2\)
Subtopic: Â Ampere Circuital Law |
 90%
Level 1: 80%+
JEE
Please attempt this question first.
Hints
Please attempt this question first.
A long, straight wire of radius \(R\) carries a current distributed uniformly over its cross-section. The magnitude of the magnetic field is:
| (a) | maximum at the axis of the wire |
| (b) | minimum at the axis of the wire |
| (c) | maximum at the surface of the wire |
| (d) | minimum at the surface of the wire. |
Choose the correct option from the given ones:
| 1. | (a) and (b) only |
| 2. | (b) and (c) only |
| 3. | (c) and (d) only |
| 4. | (a) and (d) only |
Subtopic: Â Ampere Circuital Law |
 80%
Level 1: 80%+
Hints
A long cylindrical wire carries a current \(I\) flowing uniformly along its axis, on its outer surface.
The current per unit circumference of the wire is: (refer to diagram)
The current per unit circumference of the wire is: (refer to diagram)
| 1. | \(\Large\frac{I}{\pi R^2}\) | 2. | \(\Large\frac{I}{2\pi R}\) |
| 3. | \(\Large\frac{2I}{\pi R}\) | 4. | \(\Large\frac{I}{2 R}\) |
Subtopic: Â Ampere Circuital Law |
 79%
Level 2: 60%+
Hints
- 1(current)
Q. No.
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