A circular loop of radius 7 cm is placed in uniform magnetic field of 0.2 T directed perpendicular to plane of loop. The loop is converted into a square loop in 0.5 s . The EMF induced in the loop is ___________ mV.

induced EMF \(=\frac{ d \phi}{ dt }\)
circumference \(\simeq 14 \pi\)
side length of square loop \(=\frac{14 \pi}{4}=\frac{7 \pi}{2}\)
\(\Delta \phi= B \left( A _1- A _2\right)\)
\(=(.2)\left(\left(\frac{7 \pi}{2}\right) \times \frac{7 \pi}{2}-49 \pi\right) \times 10^{-4}\)
\(=.2\left(\frac{49 \pi^2}{4}-49 \pi\right) \times 10^{-4}\)
\(\Delta \phi=.2 \times 33.07 \times 10^{-4}\)
\(=.2\left(\frac{49 \pi^2}{4}-49 \pi\right) \times 10^{-4}\)
\(\Delta \phi=.2 \times 33.07 \times 10^{-4}\)
\(\Delta \phi=6.614 \times 10^{-4}\)
\(EMF =\frac{6.614 \times 10^{-4}}{\frac{1}{2}} V=13.23 \times 10^{-4} V\)
\(EMF =1.32 mV\)