The magnetic flux through a coil is 4 10⁻⁴ ~Wb at time t =0 . It reduces to 30 % of its original value in time t second. If e.m.f. induced in the coil is 0.56 mV then the value of t is

Step-by-step solution

The magnetic flux through the coil at t = 0 is ₁ = 4 10⁻⁴ Wb , which reduces to 30 % of its initial value, giving ₂ = 0.30 4 10⁻⁴ = 1.2 10⁻⁴ Wb . The change in flux is = ₂ - ₁ = -2.8 10⁻⁴ Wb . Using Faraday's law, = - t , and the given = 0.56 10⁻³ V , we substitute: 0.56 10⁻³ = 2.8 10⁻⁴ t Solving for t , t = 2.8 10⁻⁴ 0.56 10⁻³ = 5 10⁻¹ = 0.5 s . Final answer: A