Question

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.

Answer 1

Here,
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.