A coil is placed perpendicular to a magnetic field of 5000 T . When the field is changed to 3000 T in 2 s ,…

Average induced EMF is given by, $\epsilon =N\left(\frac{∆\varphi }{t}\right)$

Also, change in flux $∆\varphi =(∆B)A$

Given: $B_i=5000 \mathrm{T}$,

$B_f=3000 \mathrm{T}$

$d=0.02 \mathrm{m} \Rightarrow r=\frac{d}{2}=0.01 \mathrm{m}$

Hence, $$

$∆\varphi =(∆B)A$

$=\left(2000\right)\pi {\left(0.01\right)}^2=0.2\pi$

EMF, $\epsilon =N\left(\frac{∆\varphi }{t}\right)\Rightarrow 22=N\left(\frac{0.2\pi }{2}\right)$

$\Rightarrow N=70$