question_answer

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 the 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

Correct Answer: A

Solution :

As temperature increases, resistance of loop increases. As a result J decreases and hence, the flux crossing the 2nd ring will decrease. As per Lenz's law this change has been opposed and as a result both the loops attract each other.