A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ù. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s.

Question

A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ù. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s. 
(a)What is the magnitude of the induced emf in the wire?
(b)  What is the magnitude and direction of the induced current in the wire?

bobpursley · Answer

You have formulas for induced EMF, and you need to use those.

However, if one considers the resistance constant, even if the length of the wire is changing, here is an alternative approach.

power= EMF^2/R
force*velocity=EMF^2/R

EMF= sqrt (force*velcity*resistance)

and current= sqrt (force*velocty/R)