Target Exam

CUET

Subject

Physics

Chapter

Alternating Current

Question:

Equal currents are flowing in four infinitely long wires. The distance between each other is the same and directions of currents are as shown in the figure. The net force on wire 2 is

Choose the correct answer from the options given below:

Options:

directed towards left

equal to that on wire 1 towards right

directed towards right

zero

Correct Answer:

directed towards right

Explanation:

The correct answer is Option (3) → directed towards right

For two parallel current-carrying wires:

$F = \frac{\mu_0 I^2}{2 \pi r}$

Wire 1 : upward, Wire 2 : downward, Wire 3 : upward, Wire 4 : downward

Forces on Wire 2:

$F_{21} = \frac{\mu_0 I^2}{2 \pi d}$ (repulsion from Wire 1 → right)

$F_{23} = \frac{\mu_0 I^2}{2 \pi d}$ (repulsion from Wire 3 → right)

$F_{24} = \frac{\mu_0 I^2}{2 \pi (2d)} = \frac{\mu_0 I^2}{4 \pi d}$ (attraction from Wire 4 → right)

Net force:

$F_{net} = \frac{\mu_0 I^2}{2 \pi d} + \frac{\mu_0 I^2}{2 \pi d} + \frac{\mu_0 I^2}{4 \pi d}$

$F_{net} = \frac{5 \mu_0 I^2}{4 \pi d}$ (towards right)

Final Answer: Net force on wire 2 is directed towards right.