Figure shows a metal rod \( \mathrm{PQ} \) resting on the smooth ra...

Figure shows a metal rod \( \mathrm{PQ} \) resting on the smooth rails \( \mathrm{AB} \)
and positioned between the poles of a permanent magnet. The rails.
the rod. and the magnetic fleld are in three mutual perpendicular
directions. A galvanometer \( \mathrm{G} \) connects the rails through a switch \( \mathrm{K} \).
Length of the rod \( =15 \mathrm{~cm}, B=0.50 \mathrm{~T} \), resistance of the closed loop
containing the rod \( =9.0 \mathrm{~m} \Omega \). Assume the field to be uniform.
(a) Suppose \( \mathrm{K} \) is open and the rod is moved with a speed of \( 12 \mathrm{~cm} \mathrm{~s}^{-1} \)
in the direction shown. Give the polarity and magnitude of the induced enf.
(b) Is there an excess charge built up at the ends of the rods when \( \mathrm{K} \) is open? What if \( \mathrm{K} \) is closed?
(c) With \( K \) open and the rod moving uniformly, there is no net force on the electrons in the rod \( P Q \) even though they do experience magnetic force due to the motion of the rod. Explain.
(d) What is the retarding force on the rod when \( K \) is closed?
(e) How much power is required (by an external agent) to keep
the rod moving at the same speed \( \left(=12 \mathrm{~cm}^{-1}\right) \) when \( \mathrm{K} \) is closed?
(f) How much power is dissipated as heat in the closed circuit?
What is the source of this power?
(g) What is the induced emf in the moving rod if the magnetic field