In: Physics
A perfectly conducting U-shaped rail is spanned by a rod which
is able to slide without friction. The rod has a mass m =1 .2 kg
and a resistanceR =2 .0?. The rod and rail sit in a uniform
magnetic ?eld of magnitude B =0 .4 T, which is out of the page as
shown in the ?gure below. The long sections of the rail are
separated by a distance W =0 .25 m. Rod
W F
Part A
(a) With reference to Faraday’s law, explain two fundamentally
di?erent ways in which an emf can be generated around the circuit
created by the rod and the rail. (b) A constant force~ F is applied
to the rod to move it to the right at a speed of v =2 .2ms 1. What
is the magnitude of the induced emf, and the direction of the
induced current in the circuit?
(c) At a later time, the force is suddenly removed. Give a
qualitative description of the subsequent motion of the rod, and
explain your reasoning.
Part B (Advanced)
Suppose the magnetic ?eld was replaced by a uniform electric ?eld,
also pointing out of the page. A force is applied to the rod to
move it along the rails. Would there be a magnetic ?eld generated?
Explain why, or why not.