Q.

As shown in the figure, P and Q are two coaxial conducting loops separated by some distance. When the switch S is closed, a clockwise current IP flows in P (as seen by E) and an induced current IQ1 flows in Q. The switch remains closed for a long time. When S is opened, a current IQ2 flows in Q. Then the direction of IQ1 and IQ2 (as seen by E) are                     [2002]

1 respectively clockwise and anti-clockwise  
2 both clockwise  
3 both anti-clockwise  
4 respectively anti-clockwise and clockwise  

Ans.

(4)

When switch S is closed, a magnetic field is set up in the space around P. The field lines threading Q increase in the direction from right to left. According to Lenz's law, IQ1 will flow so as to oppose the cause or change and flow in the anticlockwise direction as seen by E. Opposite is the case when S is opened. IQ2 will be clockwise.