JEE Main · 2025 · 29 Jan 2025 · Shift 1 · Electromagnetic Induction

For a coil of area $A$ and $N$ turns rotating with angular velocity $\omega$ about an axis perpendicular to a uniform field $\vec{B}$, the angle between the normal to the coil and $\vec{B}$ at time $t$ is $\omega t$ (taking $t=0$ when the normal is along $B$). The flux through the coil is


and the induced emf is


When $\vec{B}$ is parallel to the plane of the coil, the normal to the coil is perpendicular to $\vec{B}$, so $\omega t=\pi /2$. At this instant