The sun delivers ${10}^3<mspace\; width="1em"></mspace>w/m^2$ of electromagnetic flux to the earth's surface.  The total power that is incident on a roof of dimensions 8 m$\times$20 m will be

(1) $2.56\times {10}^4<mspace\; width="1em"></mspace>W$             (2) $6.4\times {10}^5<mspace\; width="1em"></mspace>W$

(3) $4.0\times {10}^5<mspace\; width="1em"></mspace>W$                (4) $1.6\times {10}^5<mspace\; width="1em"></mspace>W$

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:

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:

In which of the following devices, the eddy current effect is not used?
1. Electric heater
2. Induction furnace
3. Magnetic braking in train
4. Electromagnet

Two coils of self-inductance \(2~\text{mH}\) and \(8~\text{mH}\) are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is:
1. \(10~\text{mH}\)
2. \(6~\text{mH}\)
3. \(4~\text{mH}\)
4. \(16~\text{mH}\)

The current \(i\) in a coil varies with time as shown in the figure. The variation of induced emf with time would be:
     

1.		2.
3.		4.

The current \((I)\) in the inductance is varying with time \((t)\) according to the plot shown in the figure. 

Which one of the following is the correct variation of voltage with time in the coil?

1.		2.
3.		4.

A conducting square frame of side \(a\) and a long straight wire carrying current \(I\) are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity \(v.\) The emf induced in the frame will be proportional to: