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

The Milli-voltmeter reads 1mV

Explanation:

Here,

Velocity of the train, v = $180 kmh^-^1 = 50 ms^-^1$

Earth's magnetic field, B = $0.2 \times 10^-^4\ T$

Separation between the railings, l = 1 m

Induced emf, e = Bvl = $0.2 \times 10^-^4 \times 50$

                        = 10 − 3 V

So, the voltmeter will record 1 mV as the reading.