Question

Explain with reason, in which direction does the current loop KLMN move when kept near an infinitely long straight wire carrying current as shown in figure.

Answer 1

Due to interaction of current in ab and KN there will be a force of repulsion (current in opposite directions) given by

F₁ = \(\frac{\mu_0}{4\pi} \times \frac{2I_1l_2}{r_1}\)

and due to interaction between ab and LM there will be a force of attraction (currents in same direction) and given by

Clearly force of attraction F₂ is lesser than force of repulsion F₂ . Hence the coil will be repelled away from ab.

Forces on NM and KL will be equal and opposite and acting in the same plane therefore they will cancel each other.

Net repulsive force is

F₁ - F₂ = \(\frac{\mu_0I_2I_2}{4\pi} [\frac{1}{r_1 }-\frac{1}{r_2}]\)