$(a)$ Name the type of electric current generated by most of the power stations in our country.
$(b)$ Why is it preferred over the other type?
$(c)$ State the frequency of the power supply generated in India.

With the help of which law or rule can the direction of a magnetic field be known?

$A$ coil made of insulated copper wire is connected to a galvanometer. What will happen to the deflection of the galvanometer if this coil is moved towards a stationary bar magnet and then moved away from it? Give reason for your answer and name the phenomenon involved.

Give the factors on which the magnetic field produced by a current-carrying solenoid depends.

State the condition for electromagnetic induction to take place. $A$ cylindrical bar magnet is kept along the axis of a circular coil as shown in the figure. Will there be a current induced in the coil if the magnet is rotated about its axis? Discuss.

The diagram below shows a circuit containing a coil wound over a long and thin hollow cardboard tube. Copy the diagram and:
$(i)$ Show the polarity acquired by each face of the solenoid.
$(ii)$ Draw the magnetic field lines of force inside the coil and also show their direction.
$(iii)$ Mention two methods to increase the strength of the magnetic field inside the coil.