Electro magnetic induction practice · Medium

Two different coils have self inductance $\mathrm{L}_1=9 \mathrm{~mH}$ and $\mathrm{L}_2=3 \mathrm{~mH}$. At a certain instant, the current in the two coils in increasing at the same rate and the power supplied to the coils in also the same. The ratio of the energy stored in the two coils $\left(\mathrm{U}_1 / \mathrm{U}_2\right)$ at that instant is

Use of eddy currents is favoured in the following except

A $\mathrm{50}$ turns circular coil has a radius of $\mathrm{3}\,\mathrm{ cm}$, it is kept in a magnetic field acting normal to the area of the coil. The magnetic field $B$ increased from $\mathrm{0}\mathrm{.10}$ to $\mathrm{0}\mathrm{.35 T}$ in $\mathrm{2}\,\,\mathrm{millisecond}$. The average induced emf in the coil is

The inductance in a coil plays the same role as

A ring of radius a rotates with a constant angular velocity $\omega$ about its axis (passing through its centre and perpendicular to its plane). The ring is in $x-y$ plane. The potential difference induced in the ring would be zero, if uniform magnetic field is along

Consider the situation shown in figure. If the switch is closed and after some time it is opened again, the closed loop will show