Alternate Current and Direct Current

Electricity flows in two ways viz., alternating current (AC) or in a direct current (DC). Electricity or “current” is nothing but the movement of electrons through a conductor such as wire. The difference lies in the direction of the flow of electrons. In DC, while the electrons flow in a single direction, the electrons keep switching their direction (forward and backward) in case of AC.

Note. Alternating current is the best way to transmit electricity over large distances.

 

Source: www.diffen.com

 

Alternating Current	Direct Current
Safe to transfer over longer distances and provide more power	DC voltage cannot travel very far as it begins to lose energy
AC cannot be stored	Can be stored in batteries
Rotating magnet along the wire	Steady magnetism during the wire
The frequency of AC is 50Hz or 60Hz depending upon the country	The frequency is 0
It reverses its direction while flowing in a circuit	It flows in one direction in the circuit
It is the current of magnitude varying with time	It is the current of constant magnitude
Electrons keep switching the directions i.e., forward and backward	Electrons move steadily in one director or ‘forward’
AC is obtained from AC generator and mains	Cell or Battery
Impedance	Resistance only
Lies between 0 & 1	It is always 1
Sinosoidal, trapezoidal, triangulare, square	Pure and pulsating

 

A magnetic field near the wire causes electrons to flow in a single direction along the wire, because they are repelled by the negative side of a magnet and attracted towards the positive side. This is how DC power from a battery was born (attributed to Thomas Edison’s work).

AC generators gradually replaced Edison’s DC battery system because AC is safer to transfer over the longer distances and provide more power. Instead of applying the magnetism along the wire steadily, scientist Nikola Tesla used a rotating magnet. When the magnet was oriented in one direction, the electrons flowed towards the positive, but when the magnet’s orientation was flipped, the electrons turned as well.

Another difference between AC and DC involves the amount of energy it can carry. For DC, each battery is designed to produce only one voltage level, and voltage of DC cannot travel very far until it beings to lose energy. But AC on the other hand, can be bumped up or down in strength by another mechanism called a ‘transformer’. For example, AC current leaves the power plant and is transmitted at very high voltage across power lines; however, transformers located on electrical poles on the street change it into a lower voltage appropriate for home appliances like lamps and refrigerators.

AC can be changed to DC by an adaptor that you use to power the battery in your laptop. DC can be ‘bumped’ up or down. Invertors change DC to AC. For instance, for your car an inverter would change the 12 volt AC to 120 volt AC to run a small device.