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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 VI 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»

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



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