Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction. The force per unit length in N/m of one wire on the other is: A) 1 * 10^-³, repulsive B) 1 *10^-³, attractive C) 4 * 10^-⁵, repulsive D) 4 *10^-⁵, attractive E) none of these

Question

Quizplus · Accepted Answer

The force per unit length between two parallel wires carrying currents in the same direction is given by:
$$F = \frac{\mu_0 I_1 I_2}{2\pi d}$$
where $\mu_0$ is the permeability of free space, $I_1$ and $I_2$ are the currents in the wires, and $d$ is the distance between them.

Substituting the values, we get:
$$F = \frac{(4\pi 	imes 10^{-7}\mathrm{\ N/A^2})(2\mathrm{\ A})(4\mathrm{\ A})}{2\pi (0.04\mathrm{\ m})}$$
$$F = 4\mathrm{\ N/m}$$

Since the currents are flowing in the same direction, the force is attractive. Therefore, the correct answer is D) 4 N/m, attractive.

Two Parallel Wires, 4 Cm Apart, Carry Currents of 2