Differentiate between $AC$ and $DC$ along with the graph.

(N/A) The electric current which changes its direction (or polarity) after a certain fixed interval of time is called $AC$ or alternating current. In $AC$,the polarity ($+$ or $-$) is not fixed. The current $v/s$ time graph for $AC$ is shown in figure $(a)$.
The electric current which always flows in the same direction is called direct current or $DC$. In $DC$,the polarity ($+$ or $-$) is fixed. The current obtained from a battery or a cell is $DC$. The current $v/s$ time graph for $DC$ is shown in figure $(b)$.