The law of electromagnetic induction has been used in the construction of

The charge which will flow through a galvanometer of resistance $200 \Omega$ connected to a $400 \Omega$ circular coil of $1000$ turns wound on a wooden stick $20 \ mm$ in diameter,if a magnetic field $B=0.012 \ T$ parallel to the axis of the stick is decreased suddenly to zero,is nearly: (in $\mu C$)

$A$ rectangular coil of $20$ turns and area of cross section $25 \text{ cm}^2$ has a resistance of $100 \Omega$. If a magnetic field which is perpendicular to the plane of the coil changes at a rate of $100 \text{ T/s}$, the current in the coil is . . . . . . . (in $\text{ A}$)

The total charge induced in a conducting loop when it is moved in a uniform magnetic field depends on

$A$ current-carrying infinitely long wire is kept along the diameter of a circular wire loop,without touching it. The correct statement$(s)$ is (are):
$(A)$ The emf induced in the loop is zero if the current is constant.
$(B)$ The emf induced in the loop is finite if the current is constant.
$(C)$ The emf induced in the loop is zero if the current decreases at a steady rate.
$(D)$ The emf induced in the loop is finite if the current decreases at a steady rate.

$A$ magnetic field of $2 \times 10^{-2} \,T$ acts at right angles to a coil of area $100 \,cm^2$ with $50$ turns. The average e.m.f. induced in the coil is $0.1 \,V$, when it is removed from the field in time $t$. The value of $t$ is (in seconds): (in $s$)