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Following figure shows a metal rod PQ resting on the smooth ralls AH 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 15 cm, B 0.50 T, resistance of the closed loop containing the rod `9.0 mOmega`. Assume the field to be uniform. With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain. |
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Answer» Given, length of the rod `l=15cm=15xx10^(-2)m` Magnetic field `B=0.50T` Resistance of the closed - loop containing the rod, `R=9mOmega=9xx10^(-3)Omega` Velocity of rod `V=12" cm/s "12 xx 106(-2) m//s.` When key is open, there is no net force on the electrons because the presence of excess charge at P and Q sets up an electric field and magnetic forcé on the electrons is balanced by force on them due to force by the electric field. So, there is no net force on the rod. |
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