Two co-axial solenoids shown in figure. If key of primary suddenly opened then direction of instantaneous induced current in resistance ' $R$ ' which connected in secondary :-

 

As a result of change in the magnetic flux linked to the closed loop shown in the figure, an e.m.f. . $\mathrm{V}$volt is induced in the loop. The work done (joules) in taking a charge $Q$ coulomb once along the loop is :-

Figure shows three regions of magnetic field each of area $A$ and in each region magnitude of magnetic field decreases at a constant rate $\alpha$. If $\overrightarrow{E}$ is induced electric field, then value of line integral $\oint \overrightarrow{E}·\mathrm{d}\overrightarrow{r}$ along the given loop is equal to,

The drawing shows a copper wire (of negligible resistance) bent into a circular shape with a radius of $r$. The radial section $BC$ is fixed in plane, while the copper bar $AC$ sweeps around at an angular speed of $\omega$. The bar makes electrical contact with the wire at all times. The wire and the bar have negligible resistance. $A$uniform magnetic field exists everywhere, is perpendicular to the plane of the circle, and has a magnitude of $B$. Which of the following shows the magnitude of the current as a function of $\theta$ ?

As shown, a uniform magnetic field $B$ pointing out of the paper plane is confined in the shaded area of radius $r$. At a distance$R$ from the centre of the shaded area there is a point particle of mass $m$ and carrying charge $q$. The magnetic field is then quickly changed to zero. Find the speed of the particle.