Question

A metal rod of length 2 m rotates vertically about one of its end with frequency 2 Hz. The horizontal component of earth's magnetic field is 3.14 × 10^–5T then emf developed between two ends of road is........... 

(a) 78.87 × 10^–4V 

(b) 7.887 × 10^–4V 

(c) 78.87 × 10^–6V 

(d) 0V

Answer 1

The correct option (b) 7.887 × 10^–4V 

Explanation:

ℓ = 2m

f = 2 Hz

B_H = 3.14 × 10^–5T

ω = 2πf = 2π × 2 = 12.56 rad/sec

For a rotating rod. emf induced = [{Bωℓ²}/2]

∴ e = [{3.14 × 10^–5 ×12.56 × (2)²}/2]

= 78.9 × 10^–5V

e = 7.89 × 10^–4V