Question

A bar of length 2m is said to fall freely in a magnetic field of magnitude 50 T. What is the motional emf in the bar when it has fallen 40 meters?

(a) 700 V

(b) 2100 V

(c) 2800 V

(d) 1400 V

I got this question during a job interview.

The above asked question is from Electromagnetic Induction topic in portion Electromagnetic Induction of Physics – Class 12

Answer 1

Right answer is (c) 2800 V

Explanation: Given: L = 2 m; B = 50 T;

The bar is said to be falling freely, so ➔ u = 0

According to Newton’s third equation ➔ v^2 – u^2 = 2gh

v^2 = 2gh; h = 40 m

v = \(\sqrt{(2 × 9.8 × 40)}\)

v = 28 m/s

Motional emf (E) = vLB

E = 28 × 2 × 50

E = 2800 V