Question

The emf induced across the ends of a conductor due to its motion in a magnetic field is called motional emf. It is produced due to magnetic Lorentz force acting on the free electrons of the conductor. For a circuit shown in the figure, if a conductor of length l moves with velocity v in a magnetic field B perpendicular to both its length and the direction of the magnetic field, then all the induced parameters are possible in the circuit.

A 0.1 m long conductor carrying a current of 50 A is held perpendicular to a magnetic field of 1.25 mT. The mechanical power required to move the conductor with a speed of 1 ms^-1 is ______.

Options

• 62.5 mW

• 625 mW

• 6.25 mW

• 12.5 mW

Answer 1

A 0.1 m long conductor carrying a current of 50 A is held perpendicular to a magnetic field of 1.25 mT. The mechanical power required to move the conductor with a speed of 1 ms^-1 is 6.25 mW.

Explanation:

Here, l = 0.1 m, v = 1 ms^-1

I = 50 A, B = 1.25 mT = 1.25 × 10^-3 T

The induced emf is, ε = Blv

The mechanical power is 

P = εI = BlvI = 1.25 × 10^-3 × 0.1 × 1 × 50

= 6.25 × 10^-3 W

= 6.25 mW