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. \(4B\)

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 $\frac{3R}{2}$ from the axis of the cylindrical shell?

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:

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 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: