The magnetic flux of 500 $\mathrm{\mu }$Wb per turn passing through a 200 turn coil is reversed in 20 × 10^{– 3} seconds. The average e.m.f. induced in the coil in volt is 
 

Given data: A 200 turn coil experiences a $500\mu \text{Wb}$ per turn magnetic flux that reverses in $20\times {10}^{-3}$seconds.

Concept used: Electromagnetic induction.

Detailed solution:

Faraday’s law takes into account how shifting magnetic fields might result in current flowing through wires. According  to Lenz’s law of electromagnetic induction, the induced current will be directed in a way that the magnetic field it generates will oppose the initial changing magnetic field that gave rise to it.

$$\begin{gathered} \mathrm{EMF}=\text{N}\frac{\mathrm{\Delta \varphi }}{\mathrm{\Delta t}} \\ =\frac{2\times 500\times {10}^{-6}\times 200}{20\times {10}^{-3}} \\ =10 \text{V} \end{gathered}$$