If the current flows always in the same direction, it is called 'direct current'. Direction current is represented as DC or dc. The current derived from a cell or a battery is direct current - since it is unidirectional. The positive and negative terminals are fixed. If the current changes direction after equal intervals of time, it is called alternating current. Alternating current can be written as AC or ac. Most of the power stations generate alternating current. The following are the circuit elements representing dc and ac.
The difference can be learnt by drawing voltage-time graph.
The DC sources are described only in turns of the steady voltage and AC sources are described with maximum voltage and the frequency with which the voltage varies.
