The radius of a circular loop placed in a perpendicular uniform magnetic field is increasing at a constant rate of $r_0 \ m s^{-1}$. If at any instant the radius of the loop is $r$,then the emf induced in the loop at that instant will be:

$A$ conducting rod $AC$ of length $4l$ is rotated about a point $O$ in a uniform magnetic field $\vec B$ directed into the paper. $AO = l$ and $OC = 3l$. Then:

$A$ fighter plane of length $20\, m$, wing span (distance from tip of one wing to the tip of the other wing) of $15\,m$ and height $5\,m$ is flying towards east over Delhi. Its speed is $240\, ms^{-1}$. The earth's magnetic field over Delhi is $5 \times 10^{-5}\,T$ with the declination angle $\, 0^\circ$ and dip of $\theta$ such that $\sin \theta = 2/3$. If the voltage developed is $V_B$ between the lower and upper side of the plane and $V_W$ between the tips of the wings, then $V_B$ and $V_W$ are close to:

$A$ conducting rod,with a resistor of resistance $R$,is pulled with constant speed $v$ on a smooth conducting rail as shown in the figure. $A$ constant magnetic field $B$ is directed into the page. If the speed of the bar is doubled,by what factor does the rate of heat dissipation across the resistance $R$ change?

$A$ big circular coil of $1000$ turns and average radius $10 \, m$ is rotating about its horizontal diameter at $2 \, rad \cdot s^{-1}$. If the vertical component of Earth's magnetic field at that place is $2 \times 10^{-5} \, T$ and the electrical resistance of the coil is $12.56 \, \Omega$,then the maximum induced current (in $A$) in the coil will be:

$A$ thin wire of length $2 \ m$ is perpendicular to the $xy$-plane. It moves with a velocity $v = (2\hat{i} + 3\hat{j} + \hat{k}) \ m/s$ in a magnetic field $B = (\hat{i} + 2\hat{j}) \ Wb/m^2$. What is the induced potential difference (emf) across the ends of the wire?