The figure shows certain wire segments joined together to form a coplanar loop. The loop is placed in a perpendicular magnetic field in the direction going into the plane of the figure. The magnitude of the field increases with time. I1 and I2 are the currents in the segments ab and cd. Then,
(A)I1>I2
(B)I1<I2
(C)I1 is in the direction ba and I2 is in the direction cd
(D)I1 is in the direction ab and I2 is in the direction dc✓ Correct
Answer: (D)
Solution
According to Lenz's law, when the magnetic field into the plane increases, an induced current will flow to oppose this change. The induced current will create a magnetic field out of the plane, which requires a counterclockwise current in the loop. Looking at the loop, the current flows counterclockwise, so in segment ab the current flows from a to b, and in segment cd the current flows from d to c. Therefore, I1 is in the direction ab and I2 is in the direction dc.
JEE Advanced · 2009 · 12 Apr 2009 · Paper 1 · Single correct option