Electromagnetic...

In an AC generator, a coil with $$N$$ turns, all of the same area $$A$$ and total resistance $$R$$, rotates with frequency $$1 rad/s$$ in a magnetic field $$B$$. The maximum value of emf generated in the coil is:

Assertion : When two coils are wound on each other, the mutual induction between the coils is maximum.
Reason : Mutual induction does not depend on the orientation of the coils.

Two parallel rails of a railway track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is one metre. A train is traveling with a velocity of $$72 km/h$$ along the track. The reading of the millivoltmeter (in $$mV$$ ) is :

The area of a coil is $$500cm^{2}$$ and the number of turns in it is $$2000$$. It is kept perpendicular to a magnetic field of induction $$4 \times10^{-5}Wb /m^{2}$$. The coil is rotated through $$180$$ in $$0.1$$ second. If the resistance of the total circuit is $$20\Omega$$, then the value of the induced charge flowing in the circuit will be :

Assertion : When number of turns in a coil is doubled, coefficient of self inductance of the coil becomes 4 times.
Reason : This is because $$L\propto N^{2}$$ .

A current of $$2A$$ is passed through a coil of $$1000$$ turns to produce a flux of $$0.5\mu  Wb$$. Self inductance of the coil 

Two ends of a conducting rod of varying cross-section are maintained at $$200^\circ C$$ and $$0^\circ C$$ respectively, figure. In steady state

In the arrangement shown in given Figure, there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then,

For a coil having $$L = 2 mH$$, current flow through it is I = $$t^2 e^{-t}$$ then the time at which emf become zero : -

A solenoid (air core) ahs 400 turns, is 20 cm long and has a cross section of $$4 cm^2$$. Then the coefficient of self induction is approximately