Question

The coil of area 0.1 m² has 500 turns. After placing the coil in a magnetic field of strength 4×10⁻⁴Wb / m², if rotated through 90° in 0.1 s, the average emf induced in the coil is(a) 0.012 V(b) 0.05 V(c) 0.1 V(d) 0.2 V

Answer 1

cross sectional area of coil, A = 0.1 m²

number of turns , N = 500

magnetic field strength, B = 4 × 10^-4 Wb/m²

a/c to question, magnetic flux changes by rotation of coil, it is rotated through 90° in 0.1 sec

so, induced emf = - NBA(cos$\theta_f$-cos$\theta_i$)/t

= - 500 × 4 × 10^-4 × 0.1 (cos90° - cos0°)/0.1

= -(500 × 4 × 10^-4 × 0.1 )(0 - 1)/0.1

= 500 × 4 × 10^-4

= 2000 × 10^-4 = 0.2 V

hence, option (d) 0.2V is correct