A long, straight wire is in the same plane as a rectangular, conducting loop. The wire carries a constant current I as shown in the figure. Which one of the following statements is true if the wire is suddenly moved toward the loop?
A)There will be no induced emf and no induced current.
B)There will be an induced emf, but no induced current.
C)There will be an induced current that is clockwise around the loop.
D)There will be an induced current that is counterclockwise around the loop.
E)There will be an induced electric field that is clockwise around the loop.

Question

A long, straight wire is in the same plane as a rectangular, conducting loop. The wire carries a constant current I as shown in the figure. Which one of the following statements is true if the wire is suddenly moved toward the loop? 
A)There will be no induced emf and no induced current. 
B)There will be an induced emf, but no induced current. 
C)There will be an induced current that is clockwise around the loop. 
D)There will be an induced current that is counterclockwise around the loop. 
E)There will be an induced electric field that is clockwise around the loop.

Quizplus · Accepted Answer

When the wire is moved towards the loop, the magnetic field associated with the wire will change. This changing magnetic field will induce an emf in the loop, which will cause a current to flow in the loop. According to Lenz's law, this induced current will create a magnetic field that opposes the change that produced it. In this case, the induced current will create a magnetic field that opposes the wire's magnetic field. This means that the induced current will create a magnetic field that points into the page, which is a counterclockwise direction around the loop. Therefore, the correct answer is choice D.

A Long, Straight Wire Is in the Same Plane as a Rectangular