As shown in the figure,a C-shaped conductor is in a uniform magnetic field B out of the page,and the magnitude of B is increasing.What is the polarity of the induced emf in terminals X and Y?
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.

Question

As shown in the figure,a C-shaped conductor is in a uniform magnetic field B out of the page,and the magnitude of B is increasing.What is the polarity of the induced emf in terminals X and Y? 
A)X and Y are at the same potential. 
B)X is positive and Y is negative. 
C)Y is positive and X is negative.

Quizplus · Accepted Answer

According to Faraday's law of electromagnetic induction, an emf is induced in a conductor when there is a change in the magnetic flux linking the conductor. In this case, the magnetic field is increasing out of the page, which means the magnetic flux linking the conductor is also increasing. The induced current flows in such a direction as to oppose the change that caused it, which in this case is the increase in magnetic flux. By applying Lenz's law, we can determine the polarity of the induced emf. The induced current will flow clockwise in the C-shaped conductor, which generates a magnetic field that is directed into the page. This opposes the increase in the external magnetic field and produces a net magnetic field that is weaker than the external field. In order to have a weaker magnetic field, the induced magnetic field must be in the opposite direction (into the page) to the external field (out of the page). By the right-hand rule, the induced emf will be positive at Y and negative at X. Therefore, choice C is the correct answer.

As Shown in the Figure,a C-Shaped Conductor Is in a Uniform