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.

(N/A) $(i)$ Based on the direction of current flow,end $A$ acts as the North pole and end $B$ acts as the South pole.
$(ii)$ The magnetic field lines inside the solenoid are parallel to the axis of the solenoid,indicating a uniform magnetic field. The direction of the field lines is from the South pole to the North pole inside the coil.
$(iii)$ Two methods to increase the strength of the magnetic field inside the coil are:
$1$. Increase the magnitude of the current flowing through the coil.
$2$. Increase the number of turns in the coil or insert a soft iron core inside the solenoid.