Faraday's law

Description

A loop of wire travels from the left to the right through an inhomogeneous magnetic field as shown in the animation. The green vertical line at x=0 is for your reference. The induced emf in the loop is shown in Volts as is the direction of the induced current.

Question

Describe the magnetic field perpendicular to the computer screen.  

Instructor Resources

Reference: See Giancoli-PA: 21-3, Giancoli-SE: 27-3.

Answer: B_z(x<0)=constant, B_z(x>0)=constant, and B_z(x<0)< B_z(x>0). From Lenz’s law, we know that the magnetic field must be increasing out of the page across the green line. Note that some students will assume that the magnetic field on the left of the green line is zero (because the voltage shown is zero) and the magnetic field on the right is positive (out of the page).  However, this is not necessarily the case. The only thing we do know is that the magnetic field to the right of the line must be constant and greater than the constant magnetic field to the left of the line.

Script Author: Mario Belloni