JEE Mains Model Paper 14

The two rails of a railway track , insulated from each other and the ground , are connected to millivoltmeter. What is the reading of the millivoltmeter when a train passes at a speed of 180 km/hr along the track, given that the horizontal component of earth's magnetic field is 0.2 × 10−4 wb/m2 and rails are separated by 1 metre