Two long parallel wires are at a distance of \(1\) m. If both of them carry one ampere of current in the same direction, then the force of attraction on the unit length of the wires will be:
1. \(2\times10^{-7}\) N/m
2. \(4\times10^{-7}\) N/m
3. \(8\times10^{-7}\) N/m
4. \(10^{-7}\) N/m
| 1. | \(4\) times | 2. | \(\dfrac{1}{4}\) times |
| 3. | \(8\) times | 4. | \(\dfrac{1}{8}\) times |
| 1. | \(\dfrac{\mu_{0} i^{2} L}{2 \pi r}\) | 2. | \(\dfrac{\mu_{0} i^{2} L}{4 \pi r}\) |
| 3. | \(\dfrac{\mu_{0} i^{2} L}{2 r}\) | 4. | \(\dfrac{\mu_{0} i^{2} L}{4 r}\) |
Consider the situation shown in the figure. The straight wire is fixed but the loop can move under magnetic force. The loop will:

| 1. | remain stationary |
| 2. | move towards the wire |
| 3. | move away from the wire |
| 4. | rotate about the wire |
Two long, thin, parallel conductors are separated by a distance \(d\) and carry currents \(i_1\) and \(i_2,\) respectively. The force per unit length \(F\) acting on one conductor is analysed under the following conditions:
| (A) | The force \(F\) is attractive, if \(i_1\) and \(i_2\) flow in the same direction. |
| (B) | The force \(F\) is attractive, if \(i_1\) and \(i_2\) flow in opposite directions. |
| (C) | The magnitude of the force \(F\) is the same for both conductors. |
| (D) | The magnitude of the force \(F\) is different for the two conductors. |
| 1. | (A) and (C) only |
| 2. | (A) and (B) only |
| 3. | (B) and (D) only |
| 4. | (B), (C) and (D) only |
| 1. | \(4\times 10^{-5}~\text{N/m}\) | 2. | \(6\times 10^{-5}~\text{N/m}\) |
| 3. | \(6\times 10^{-6}~\text{N/m}\) | 4. | \(6\times 10^{-4}~\text{N/m}\) |