Question

Draw the magnetic field lines due to two straight, long, parallel conductors carrying currents I₁ and I₂ in the same direction. Write an expression for the force acting per unit length on one conductor due to other. Is this force attractive or repulsive?

(ii) Figure shows a rectangular current-carrying loop placed 2 cm away from a long, straight, current-carrying conductor. What is the direction and magnitude of the net force acting on the loop?

Answer 1

(i) The magnetic field lies due to two current carrying parallel wires are shown in figure. 

The force between parallel wires \(\frac{F}{l}=\frac{\mu_0I_1I_2}{2\pi r}N/m\)

(ii) We know that parallel currents attract and opposite currents repel and F∝1/r. As wire of loop carrying opposite current is nearer, so the net force acting on the loop is repulsive.