# Q6.14 (a) Figure shows a metal rod $PQ$  resting on the smooth rails $AB$ and positioned between the poles of a permanent magnet. The rails, 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 $rod=15cm$ ,  $B=0.50T$, resistance of the closed loop containing the $rod=9.0m\Omega$ . Assume the field to be uniform. Suppose K is open and the rod is moved with a speed of $12cm\: s^{-1}$ in the direction shown. Give the polarity and magnitude of the induced emf.

P Pankaj Sanodiya

Given

Length of the rod

$l=15cm=0.15m$

Speed of the rod

$v=12cm/s=0.12m/s$

Strength of the magnetic field

$B=0.5T$

induced emf in the rod

$e=Bvl=0.5*0.12*0.15=9*10^{-3}V$

Hence 9mV emf is induced and it is induced in a way such that P is positive and Q is negative.

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