The AC (Alternate Current) and the DC(Direct Current) are not only the subject matters of physics but also the part of the daily jargon of the common people. So what are AC and DC?
Let us see the DC first. The DC is the flow of the current in one direction. Here the voltage has a constant polarity. It means there are definite negative and positive poles. So the flow is unidirectional and hence the name: Direct Current. For example, the batteries supply the DC. Other examples are dynamos, solar cells, thermocouples.
In the AC, the direction of the flow of the current keeps alternating. The polarity of the terminals also keeps alternating.From positive to negative and vice versa. That is why it is called the Alternating Current. Our domestic electric supply is a good example of AC. All our offices and the industries are running over the AC.
The constant and the alternating polarity or the direction of the current is shown below. It clearly depicts the basic difference between these two types of currents.
The conversion of the DC into the AC and vice versa is possible. To convert an AC into a DC we need a rectifier that restricts the current to flow in two directions and for converting a DC into an AC we need an inverter or a motor generator set.
Developing power distribution systems in the AC is easier. To develop generators and motors in the AC is also more convenient.That is why the AC dominates all over the world.
The DC is chiefly used in electronic pieces of equipment like cell phones, laptops, flat screen TV’s (An AC enters and is converted into a DC).
The AC could show several waveforms. If we plot the voltage of an AC over time, it could be a sine wave, square wave or triangle wave. The AC in most of the homes and offices is the sine wave AC. Square waves are used in digital and switching electronics systems.Triangle waves are used in the acoustics. But the plot of the DC voltage is a straight line. Simple.