Magnetic flux (in weber) in a closed circuit of resistance 20 Ω varies with time t s as ϕ = 8 t 2 - 9 t + 5 . The magnitude of the induced current at t = 0 . 25 s will be _____ mA .

Step-by-step solution

Given that magnetic flux ϕ = 8 t 2 - 9 t + 5 According to Faraday's law of electromagnetic induction emf = - d ϕ d t = - 16 t - 9 At t = 0 . 25   s emf = - 16 × 0 . 25 - 9 = 5   V Current = emf     Resistance   = 5   V 20   Ω = 1 4   A = 1000 4   mA = 250   mA