What is rectifier? What are the types of it?

The diagram below shows a dual control switch circuit connected to a bulb. Out of A & B which one is the live wire and which one is the neutral wire? 

In our daily life we use two types of electric current whose current-time graphs are given below :

(i) Name the type of current in two cases.

(ii) Identify any one source for each type of current.

(iii) What is the frequency of current in case (b) in our country?

(iv) On the basis of these graphs, list two differences between the two currents.

(v) Out of the two which one is used in transmitting electric power over long distances and why?

You are given following current $\left(I\right)$ - time $\left(t\right)$graphs.

(a) Name the type of current in each case.

(b) Identify one source for each of the currents.