Two parallel rails of a railway track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is 1 m. A train is travelling with a velocity of `72 kmh^(-1)` along the track. The reading of the millivoltmeter (in mV) is (Vertical component of the earth's magnetic induction is 2`xx10^(-5)T`

Options

A. 1.44
B. 0.72
C. 0.4
D. 0.2

Answer

C

Explanation

Induced emf, e=BVl
`V=72km/h=72xx5/18=20ms^(-1),l=1m`
`e=2xx10^(-5)xx20xx1`
`=40xx10^(-5)V`
`=0.4mV`