When a wire loop is rotated in a magnetic field,the direction of induced $emf$ changes in every

$A$ circular coil of mean radius $7 \, cm$ and having $4000$ turns is rotated at the rate of $1800$ revolutions per minute in the earth's magnetic field $(B = 0.5 \, \text{gauss})$. The maximum $e.m.f.$ induced in the coil will be .... $V$.

What is the phase difference between the flux linked with a coil rotating in a magnetic field and the induced emf produced in it?

At the centre of a fixed large circular coil of radius $R$,a much smaller circular coil of radius $r$ is placed. The two coils are concentric and are in the same plane. The larger coil carries a current $I$. The smaller coil is set to rotate with a constant angular velocity $\omega$ about an axis along their common diameter. Calculate the $emf$ induced in the smaller coil after a time $t$ of its start of rotation.

$A$ ring of resistance $10 \ \Omega$,radius $10 \ cm$ and $100$ turns is rotated at a rate of $100$ revolutions per second about its diameter perpendicular to a uniform magnetic field of induction $10 \ mT$. The amplitude of the current in the loop will be nearly $....... \ A$. (Take: $\pi^2 = 10$)

$A$ student pedals a stationary bicycle. The pedals of the bicycle are attached to a $100$ turn coil of area $0.10$ $m^2$. The coil rotates at half a revolution per second and it is placed in a uniform magnetic field of $0.01$ $T$ perpendicular to the axis of rotation of the coil. What is the maximum voltage generated in the coil (in $V$)?