The figure below shows two parallel conducting rails, oriented vertically, conne
ID: 1265160 • Letter: T
Question
The figure below shows two parallel conducting rails, oriented vertically, connected to each other at the top by a wire with a resistance R. A conducting metal rod is oriented horizontally and is in contact with the two vertical rails. The horizontal rod has a length
L = 50.0 cm
and mass 35.0 g. The rod is released from rest at location A and begins to fall through a region of uniform magnetic field indicated by the shaded area in the figure. When the rod reaches point B, there is an induced current of 1.85 A flowing to the right in the rod, and the rod is moving downward with an acceleration of magnitude 7.85 m/s2.
What are the direction and magnitude of the magnetic field in the shaded region?
Explanation / Answer
By Faraday's law. direction of field is into the page.
If, the magnitude is B,
Equating force on the rod using Newton's second law,
BIL = F=m(g-f)
B is the magnitude of the magnetic field, I is the current and L is the length of the rod, m is its mass, f is its acceleration, g= gravitational acceleration
or, B*1.85*0.5= 35/1000*(9.81 - 7.85)
or, B=0.074162 Tesla