Question

Two circular loops of equal radii are placed coaxially at some separation. The first is cut and a battery is inserted in between to drive a current in it. The current changes slightly because of the variation in resistance with temperature. During this period, the two loops-
(a) Attract each other
(b) Repel each other
(c) Do not exert any force on each other
(d) Attract or repel each other depending on the sense of the current.

Answer 1

If current is passing from one loop then there will be a magnetic field and due to which one induced current will be there and direction of induced current in the loop can be determined by lenz’s law.

Complete step by step answer:
Consider two loops A and B placed coaxially (as shown). Let the direction of current in Loop A is clockwise when a battery is connected to it.

Now, according to the right hand screw rule, we find the direction of the magnetic field due to this current. The direction of current will be towards the left. Now resistance is increasing with temperature then current through this loop will decrease. So, the magnetic field will also decrease with time. This changing current will induce some current in the loop B. Now, according to the lenz’s law the direction of the induced current in loop B will be in such a way that it will oppose the decrease in the magnetic field which is due to loop A. So, current will be induced in clockwise direction in loop B. Direction of the currents in the both loops is the same, they will attract each other.

So, the option$\left( A \right)$ is correct.

Note: Lenz’s law states that the direction of induced current in such a way that it will oppose the cause of its production.
Right hand screw rule- Consider one screw is held in the right hand in such a way that it will move in the direction of the current and direction of the magnetic field will be the same as of the rotation of the screw.