Question

Magnetic flux through a coil changes from \(8\ \mathrm{mWb}\) to \(2\ \mathrm{mWb}\) in \(0.2\ \mathrm{s}\). What is the induced emf?

• A. \(15\ \mathrm{mV}\)
• B. \(30\ \mathrm{mV}\)
• C. \(20\ \mathrm{mV}\)
• D. \(25\ \mathrm{mV}\)

Hint:

Faraday's law: \[ \boxed{ E=\left|\frac{\Delta\Phi}{\Delta t}\right| } \] where \(\Phi\) is the magnetic flux.

Answer 1

The Correct Option is B

Step 1: Apply Faraday's law of electromagnetic induction. The magnitude of induced emf is \[ E=\left|\frac{\Delta\Phi}{\Delta t}\right|. \] Here, \[ \Delta\Phi=(8-2)\ \mathrm{mWb}=6\times10^{-3}\ \mathrm{Wb}, \] and \[ \Delta t=0.2\ \mathrm{s}. \]

Step 2: Calculate the induced emf. \[ E=\frac{6\times10^{-3}}{0.2} =3\times10^{-2}\ \mathrm{V} =30\ \mathrm{mV}. \] Hence, \[ \boxed{30\ \mathrm{mV}} \] Therefore, \[ \boxed{(B)} \] is the correct answer.