In the figure, a C-shaped conductor is in a uniform magnetic field B, which is increasing. The polarity of the induced emf in terminals X and Y is
A) X and Y are at the same potential.
B) X is positive and Y is negative.
C) X is negative and Y is positive.

Question

In the figure, a C-shaped conductor is in a uniform magnetic field B, which is increasing. The polarity of the induced emf in terminals X and Y is 
A) X and Y are at the same potential. 
B) X is positive and Y is negative. 
C) X is negative and Y is positive.

Quizplus · Accepted Answer

As the magnetic field is increasing, the induced emf opposes the change in flux. According to the Lenz's law, the direction of the induced current is such that it creates a magnetic field to oppose the change in the external magnetic field. Therefore, in this case, the induced current flows in a direction such that the magnetic field produced by it opposes the external magnetic field. By the right-hand rule, the direction of the induced current is clockwise when viewed from the left side of the conductor. This means that the potential at the X end of the conductor is negative (due to the current flowing from Y to X), and the potential at the Y end is positive (due to the current flowing from X to Y). Therefore, the correct choice is C, X is negative and Y is positive.

In the Figure, a C-Shaped Conductor Is in a Uniform