What is the frequency of $220 \ V$ $DC$ voltage? (In $Hz$)

The diagram below shows a coil connected to a centre zero galvanometer $G$. The galvanometer shows a deflection to the right when the $N$ pole of a powerful magnet is moved to the right as shown.
$(i)$ Explain why the deflection occurs in the galvanometer.
$(ii)$ Does the direction of current in the coil appear clockwise or anticlockwise when viewed from end $A$?
$(iii)$ State the observation in $G$ when the coil is moved away from $N$.
$(iv)$ State the observation in $G$ when,both coil and the magnet,are moved to the right at the same speed.

For the circular coil carrying current shown alongside,draw magnetic field lines. Decide which of its face behaves as North Pole and which face as South Pole. Give reason to justify your answer.

An electric generator works on the principle of electromagnetic induction.

State one main difference between $AC$ and $DC$. Why is $AC$ preferred over $DC$ for long-range transmission of electric power? Name one source each of $DC$ and $AC$.

On which principle does an electric bell work?