$A$ conducting ring is placed around the core of an electromagnet as shown in the figure. When key $K$ is pressed,the ring

As shown in the figure,a magnet is moved with a fast speed towards a coil at rest. Due to this,the induced electromotive force,induced current,and induced charge in the coil are $E$,$I$,and $Q$ respectively. If the speed of the magnet is doubled,which of the following statements is incorrect?

It is desired to measure the magnitude of the magnetic field between the poles of a powerful loudspeaker magnet. $A$ small flat search coil of area $2 \; cm^{2}$ with $25$ closely wound turns is positioned normal to the field direction and then quickly snatched out of the field region. (Equivalently,one can give it a quick $90^{\circ}$ turn to bring its plane parallel to the field direction). The total charge flown in the coil (measured by a ballistic galvanometer connected to the coil) is $7.5 \; mC$. The combined resistance of the coil and the galvanometer is $0.50 \; \Omega$. Estimate the field strength of the magnet.

$A$ coil has an area of $0.05\,m^2$ and it has $800\,turns$. It is placed perpendicularly in a magnetic field of strength $4 \times 10^{-5}\,Wb/m^2$. It is rotated through $90^o$ in $0.1\,s$. The average emf induced in the coil is ........... $V.$

$A$ uniform magnetic field $B$ that is perpendicular to the plane of the page passes through the loops,as shown. The field is confined to a region of radius $a$,where $a < b$,and is changing at a constant rate. The induced $emf$ in the wire loop of radius $b$ is $\varepsilon$. What is the induced $emf$ in the wire loop of radius $2b$?

$A$ coil of $40 \ \Omega$ resistance has $100$ turns and a radius of $6 \ mm$. It is connected to an ammeter of resistance $160 \ \Omega$. The coil is placed perpendicular to a magnetic field. When the coil is taken out of the field,a charge of $32 \ \mu C$ flows through it. The intensity of the magnetic field is: (in $T$)