The two rails of a railway track, insulated from each other and the ground, are connected to a milli voltmeter. What is the reading of the milli voltmeter when a train travels at a speed of `180 km//hours` along the track, given that the vertical components of earth's magnitic field is `0.2xx10^(_4) weber//m^(2)` & the rails are separated by 1 meter?

Options

A. 0.5 V
B. 5 mV
C. 3 mV
D. 1 mV

Answer

D

Explanation

`v = 180 kmh = (180 xx 1000)/(60 xx 60) = 50 m//s`
The voltmeter reads the induced voltage between the rails.
`e = B_(v)lv=0.2 xx 10^(-4) xx 1 xx 50 = 10^(-3) V = 1mV`.