Magnetic flux linked with the coil in weber is given by the equation $\phi = 5t^2 + 6t + 11$. The e.m.f. induced in the coil in the $5^{\text{th}}$ second will be (in $\text{ V}$)

$A$ metallic ring is placed in a room. When the north pole of a magnet is brought near to it,the induced current in the ring will be

$A$ rectangular loop of length $2.5 \ m$ and width $2 \ m$ is placed at $60^{\circ}$ to a magnetic field of $4 \ T$. The loop is removed from the field in $10 \ s$. The average emf induced in the loop during this time is

An electric generator is based on . . . . . .

The induced $emf$ can be produced in a coil by:
$A.$ Moving the coil with uniform speed inside a magnetic field.
$B.$ Moving the coil with non-uniform speed inside a uniform magnetic field.
$C.$ Rotating the coil inside a uniform magnetic field.
$D.$ Changing the area of the coil inside a uniform magnetic field.
Choose the correct answer from the options given below:

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.