If a coil of $40$ turns and area $4 \, cm^2$ is suddenly removed from a magnetic field,it is observed that a charge of $2 \times 10^{-4} \, C$ flows through the coil. If the resistance of the coil is $80 \, \Omega$,the magnetic flux density in $Wb \, m^{-2}$ is:

In electromagnetic induction,the induced charge in a coil is independent of

$A$ long solenoid having $100$ turns per $cm$ carries a current of $\frac{4}{\pi} \,A$. At the centre of it is placed a coil of $200$ turns of cross-sectional area $25 \,cm^2$ having its axis parallel to the field produced by the solenoid. When the direction of the current in the solenoid is reversed within $0.04 \,s$, the induced emf in the coil is (in $\,V$)

$A$ square loop of side $10 \ cm$ and resistance $0.7 \ \Omega$ is placed vertically in the east-west plane. $A$ uniform magnetic field of $0.20 \ T$ is set up across the plane in the north-east direction. The magnetic field is decreased to zero in $1 \ s$ at a steady rate. Then,the magnitude of the induced emf is $\sqrt{x} \times 10^{-3} \ V$. The value of $x$ is . . . . . . .

Two identical coaxial circular loops carry current $i$ each circulating in the clockwise direction. If the loops are approaching each other,then

$A$ conducting coil having $500$ turns has a cross-sectional area of $0.15 \ m^2$. $A$ magnetic field of strength $0.2 \ T$ linked perpendicular to this area changes to $1.0 \ T$ in $0.4 \ s$. The induced emf produced in the coil will be . . . . . . $V$.