The two rails of a railway track, insulated from each other and from the ground, are connected to a millivoltmeter. What will be the reading of the millivoltmeter when a train travels on the track at a speed of 180 km h−1? The vertical component of earth's magnetic field is 0.2 × 10−4 T and the rails are separated by 1 m.
Velocity of the train, v = 180 km/h = 50 m/s
Earth's magnetic field, B = 0.2 × 10−4 T
Separation between the railings, l = 1 m
Induced emf, e = Bvl = 0.2 × 10−4 × 50 = 10−3 V
So, the voltmeter will record 1 mV as the reading.
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