The magnetic flux linked with a stationary closed coil of resistance 5 Ω varies with time t according to the equation Φ = 6t² + 7t + 1 (where Φ is in Weber and t is in seconds). What is the magnitude of the induced current in the coil at t = 2 s?

Answer and explanation

Correct answer: B. 6.2 A

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  1. Step 1: According to Faraday's law of electromagnetic induction, the magnitude of induced electromotive force (EMF) is given by: .
  2. Step 2: Differentiate the flux equation with respect to time :
  3. Step 3: At time :
  4. Step 4: Using Ohm's law, the magnitude of induced current in the coil of resistance is:
Answer
6.2 A
Why not the others: '31 A' is the induced EMF in volts rather than current (forgets to divide by resistance ); '15.5 A' divides by 2 instead of 5; '3.1 A' incorrectly evaluates as before dividing by 5.

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