$A$ thin strip $10\, cm$ long is on a $U$ shaped wire of negligible resistance and it is connected to a spring of spring constant $0.5\, N/m$ (see figure). The assembly is kept in a uniform magnetic field of $0.1\, T$. If the strip is pulled from its equilibrium position and released, the number of oscillations it performs before its amplitude decreases by a factor of $e$ is $N$. If the mass of the strip is $50\, g$, its resistance $10\, \Omega$ and air drag is negligible, $N$ will be close to:

$A$ rectangular conducting loop of sides $8\, cm$ and $2\, cm$ with a small cut is moving out of a region of uniform magnetic field of magnitude $0.3\, T$ directed normal to the loop as shown in figures $(i)$ and $(ii)$. If the velocity of the loop is $1\, cm\, s^{-1}$,then the ratio of the voltage developed across $ab$ in case $(i)$ to case $(ii)$ is:

The loops have lengths $L$ or $2L$. All loops enter a magnetic field $\vec{B}$ with the same velocity $v$. Which of the following is correct?

$A$ conducting rod of length $2l$ is rotating with constant angular speed $\omega$ about its perpendicular bisector. $A$ uniform magnetic field $\vec{B}$ exists parallel to the axis of rotation. The $e.m.f.$ induced between two ends of the rod is

$A$ metallic rod of length $20 \,cm$ is placed in the North-South direction and is moved at a constant speed of $20 \,m/s$ towards the East. The horizontal component of the Earth's magnetic field at that place is $4 \times 10^{-3} \,T$ and the angle of dip is $45^{\circ}$. The emf induced in the rod is ............. $mV$.

$A$ rectangular conducting loop of length $4 \ cm$ and width $2 \ cm$ is in the $xy$-plane,as shown in the figure. It is being moved away from a thin and long conducting wire along the direction $\frac{\sqrt{3}}{2} \hat{x} + \frac{1}{2} \hat{y}$ with a constant speed $v$. The wire is carrying a steady current $I = 10 \ A$ in the positive $x$-direction. $A$ current of $10 \ \mu A$ flows through the loop when it is at a distance $d = 4 \ cm$ from the wire. If the resistance of the loop is $0.1 \ \Omega$,then the value of $v$ is. . . . . . $ms^{-1}$.
[Given: The permeability of free space $\mu_0 = 4 \pi \times 10^{-7} \ NA^{-2}$]