Two conducting circular loops of radii R₁ and R₂ are placed in the same plane with their centres coinciding. If R₁ >> R₂, the mutual inductance M between them will be directly proportional to 

(1) R₁/R₂

(2) R₂/R₁

(3) $R_1^2/R_2$

(4) $R_2^2/R_1$

In which of the following devices, the eddy current effect is not used?

A \(800\) turn coil of effective area \(0.05~\text{m}^2\) is kept perpendicular to a magnetic field \(5\times 10^{-5}~\text{T}\). When the plane of the coil is rotated by \(90^{\circ}\)$$around any of its coplanar axis in \(0.1~\text{s}\), the emf induced in the coil will be:
1. \(0.02~\text{V}\)
2. \(2~\text{V}\)
3. \(0.2~\text{V}\)
4. \(2\times 10^{-3}~\text{V}\)

A cycle wheel of radius \(0.5\) m is rotated with a constant angular velocity of \(10\) rad/s in a region of a magnetic field of \(0.1\) T which is perpendicular to the plane of the wheel. The EMF generated between its centre and the rim is:
1. \(0.25\) V
2. \(0.125\) V
3. \(0.5\) V
4. zero

The magnetic flux linked with a coil (in Wb) is given by the equation \(\phi=5 t^2+3 t+60\). The magnitude of induced emf in the coil at \(t=4\) s  will be:
1. \(33\) V
2. \(43\) V
3. \(108\) V
4. \(10\) V

A wheel with \(20\) metallic spokes, each \(1\) m long, is rotated with a speed of \(120\) rpm in a plane perpendicular to a magnetic field of \(0.4\) G. The induced emf between the axle and rim of the wheel will be:
\((1~\mathrm{G}=10^{-4}~\mathrm{T})\)
1. \(2.51 \times10^{-4}\) V
2. \(2.51 \times10^{-5}\) V
3. \(4.0 \times10^{-5}\) V
4. \(2.51\) V

The current in an inductor of self-inductance \(4~\text{H}\) changes from \(4~ \text{A}\) to \(2~\text{A}\) in \(1~ \text s\). The emf induced in the coil is:
1. \(-2~\text{V}\)
2. \(2~\text{V}\)
3. \(-4~\text{V}\)
4. \(8~\text{V}\)

The dimensions of mutual inductance \((M)\) are:
1. \(\left[M^2LT^{-2}A^{-2}\right]\)
2. \(\left[MLT^{-2}A^{2}\right]\)
3. \(\left[M^{2}L^{2}T^{-2}A^{2}\right]\)
4. \(\left[ML^{2}T^{-2}A^{-2}\right]\)