A rectangular coil of $N$ turns, area $A$, rotates at angular velocity $\omega$ in uniform field $B$. Flux: $\Phi = NBA\cos(\omega t)$ (taking $\theta = 0$ at $t = 0$ when coil plane is perpendicular to $B$). Induced EMF: $\varepsilon = NBA\omega\sin(\omega t) = \varepsilon_0\sin(\omega t)$ where $\varepsilon_0 = NBA\omega$ is the peak EMF. The EMF is maximum when the coil plane is parallel to $B$ ($\omega t = \pi/2$) and zero when perpendicular to $B$ ($\omega t = 0$). Frequency $f = \omega/(2\pi)$, period $T = 2\pi/\omega$.