In a magnetic field of 0.05T, area of a coil changes from 101 cm² to 100 cm² without changing the resistance which is 2$\mathrm{\Omega }$ . The amount of charge that flow during this period is 
 

Given data: magnetic field- 0.05T, changing coil from $101 {\text{cm}}^2\text{ to }100 {\text{cm}}^2$, constant resistance $2\Omega$

Concept used: Electromagnetic induction.

Detailed solution:

Faradays law considers how varying magnetic fields could cause electricity to flow via wires. The induced current will be positioned in accordance with lenz’s law of electromagnetic induction such that the magnetic field it produces will be in opposition to the changing magnetic field that first caused it.

Changing coil’s area $\Delta \text{A}=101-1001 {\text{cm}}^2={10}^{-4} {\text{m}}^2$

Flux change $\Delta \varphi =\text{B}\Delta \text{A}=0.05\times {10}^{-4}=5\times {10}^{-6} \text{Wb}$

$$\begin{gathered} \text{q}=\frac{\Delta \varphi }{\text{R}} \\ \therefore \text{q}=\frac{5\times {10}^{-6}}{2}=2.5\times {10}^{-6}\text{C} \end{gathered}$$