A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 m s⁻¹ at right angles to the horizontal component of the earth’s magnetic field, 0.30 x 10⁻⁴ Wb m⁻². (a) What is the instantaneous value of the emf induced in the wire? (b) What is the direction of the emf? (c) Which end of the wire is at the higher electrical potential?

Length of the wire, 1 = 10 m

Falling speed of the wire, v = 5.0 m/s

Magnetic field strength, B = 0.3 x 10^-4 Wb m^–2

Ans (a).

Emf induced in the wire, e = Blv = 0.3 x 10^-4 x 5 x 10 = 1.5 x 10^-3 V

Ans (b).

Using Fleming’s right hand rule, it can be inferred that the direction of the induced emf is from West to East.

Ans (c).

The eastern end of the wire is at a higher potential.