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# Figure shows a metal rod PQ resting on the smooth rail AB and positioned between the poles of a permanent magnet. The rail, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = $9.0 m \Omega$. Assume the field to be uniform. Is there an excess charge built up at the ends of rods, when k is open ? What if k is closed ?

(a) YES; when the key is open, excess charge builds at the ends.
(b) NO; when the key is open, no excess charge builds at the ends. When the key is closed, no current flows.
(c) YES; when the key is open, excess charge develops at the ends When the key is closed, induced current flows and maintains the excess charge.
(d) NO; no excess chrge is build up whne the key is open. when the key is closed, induced current flows and maintains the excess charge.