Consider a solenoid coil with $N= 10$ turns with radius $12 \times 10^{−2}m$. The solenoid is subjected to a varying magnetic field that changes uniformly from $5 T \rightarrow 2 T$ in an interval of $12 s$. The axis of the solenoid makes an angle of $13 ^{\circ}$ to the magnetic field. If the angle is changed to $67 ^{\circ}$, what would the radius need to be for the emf to remain the same?

Question

$\begin{array}{1 1} 0.1994\;m \\ 0.1894\;m \\ 0.5994 \;m \\ 0.0359\;m\end{array}$