A square loop, carrying a steady current $I$, is placed in a horizontal plane near a long straight conductor carrying a steady current $I_1$ at a distance $d$ from the conductor as shown in figure. The loop will experience

• A

  a net repulsive force away from the conductor
• B

  a net torque acting upward perpendicular to the horizontal plane
• C

  a net torque acting downward normal to the horizontal plane
• Correct answer
  D

  a net attractive force towards the conductor

Solution

$$ \begin{aligned} & \mathbf{F}_2=-\mathbf{F}_4 \\ & \mathbf{F}_1=\frac{\mu_0 I_1 I l}{2 \pi d} \\ & \mathbf{F}_2=\frac{\mu_0 I_1 I l}{2 \pi(d+l)} \\ & \mathbf{F}_1>\mathbf{F}_3 \\ & F_{\text {net }}=F_1-F_3 \end{aligned} $$ So, wire atrract loop.

Hence, the correct answer is option: 'D'.