Alternating Current (AC) vs. Direct Current (DC)

An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). The common symbol for current is the uppercase letter I . The standard unit is the ampere, symbolized by A . One ampere of current represents one coulomb of electrical charge (6.24 X 10 ^∧ 18 charge carriers) moving past a specific point in one second.

Electricity flows in two ways: either in an alternating current (AC) or in a direct current (DC). The difference between AC and DC lies in the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction , or "forward". In AC, electrons keep switching directions , sometimes going "forward" and then going "backward". Although a DC current can increase or decrease, it can never reverse direction. Once a current reverses direction, it has become an AC current.

Alternating Current (AC)

Alternating current describes the flow of charge that changes direction periodically . As a result, the voltage level also reverses along with the current. AC can be identified in wave form called as sine wave , in other words it can be said as the curved line. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. These types of alternating current carry information encoded (or modulated) onto the AC signal , such as sound (audio) or images (video). These currents typically alternate at higher frequencies than those used in power transmission.

AC is the most commonly used and most preferred electric power for household equipment office and buildings, etc. In North America, AC is 120 volts and 60 hertz or cycles per second. This means it changes direction 60 times per second. In Europe, it is generally 50 hertz with 220 to 240 volts.

Direct Current (DC)

When the electric charge inside the conductor flows in one direction, then such type of current is called direct current (DC). It is produced from sources such as batteries , power supplies, solar cells, thermocouples or dynamos. Direct current may flow in a conductor such as a wire, but can also flow through insulators, semiconductors, or vacuum as in electron or ion beams . Direct current may be obtained from an alternating current supply by use of a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction.

Direct current may be converted into alternating current with an inverter or a motor-generator set. DC is used to power digital electronics , which includes cell phones and computers. Even desktop computer uses a power supply to convert the AC household current into DC to power the electronics. DC can be stored for later use in batteries and power cells.

1. DC exhibits straight line waveform whereas AC exhibits sine waveform
   
   
2. DC is unidirectional but AC reverses its direction
   
   
3. Power Factor of DC is always 1 while AC lies between 0 & 1.
   
   
4. DC is pulsating whereas AC could be Trapezoidal
   
   
5. The frequency of DC will be zero while AC will be either 50Hz or 60Hz depending upon the country.
   
   

However if you ever see a device stating "AC/DC" on the side, this means it can run on either type of current.