A coil of effective area 3 m ^2 is placed at right angles to a magnetic field of induction 0.05 Wb/m ^2 . If the field is decreased to 20 % of its original value in 10 second, the e.m.f. induced in the coil will be

Step-by-step solution

Initial magnetic flux, ₁ = B₁ A = 0.05 3 = 0.15 Wb Final magnetic field is 20 % of its original value, so B₂ = 0.20 0.05 = 0.01 Wb/m ^2 Final magnetic flux, ₂ = B₂ A = 0.01 3 = 0.03 Wb Magnitude of induced e.m.f. is given by Faraday's law of induction: e = | - t | = ₁ - ₂ t Substituting the values: e = 0.15 - 0.03 10 = 0.12 10 = 0.012 V e = 12 mV Answer: 12 mV