What is the nature of the magnetic field lines inside a current-carrying solenoid?

What is the difference between a direct current and an alternating current? How many times does $AC$ used in India change direction in one second?

The diagram below shows two ways of connecting three bulbs $A, B$ and $C$ to a $220 \,V$ main in a room. Name the two arrangements. Which of them would you prefer for household electricity? Give two reasons.

The figure below shows a current-carrying loop passing through a sheet of cardboard. Draw three magnetic field lines on the cardboard.
Give two factors on which the magnitude of the magnetic field at the centre of the loop depends.

$(a)$ Name two electrical appliances of daily use in which an electric motor is used.
$(b)$ Name and state the principle on which an electric motor works.

$(a)$ Define electromagnetic induction.
$(b)$ Two coils $P$ and $S$ are wound over the same iron core. Coil $P$ is connected to a battery and a key,and coil $S$ is connected to a galvanometer. Draw a suitable diagram of this arrangement and write your observations when:
$(i)$ current in the coil $P$ is started by closing the key.
$(ii)$ current continues to flow in coil $P$.
$(iii)$ current in coil $P$ is stopped by removing the key.
Explain the reason for such observations.