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what is different between AC and DC?

Electricity flows in two ways; either in alternating current (AC) or in direct current (DC). Electricity or 'current' is nothing more than moving electrons along a conductor, like a wire, that have been harnessed for energy. Therefore, the difference between AC and DC has to do with 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 "forwards" and then going "backwards."

Comparison chart

Alternating Current

Direct Current

Frequency:

The frequency of alternating current in India is about 50Hz.

The frequency of direct current is zero.

Obtained from:

A.C Generator and mains

Cell or Battery

Amount of energy that can be carried:

Safer to transfer over longer city distances and can provide more power

Voltage of DC cannot travel very far until it begins to lose energy

Flow of Electrons:

Electrons keep switching directions - forward and backward

Electrons move steadily in one direction or 'forward'

Cause of the direction of flow of electrons:

Rotating magnet along the wire

Steady magnetism along the wire

Current:

It is the current of magnitude varying with time

It is the current of constant magnitude

Direction:

It reverses its direction while flowing in a circuit

It flows in one direction in the circuit

Types:

Sinusoidal, Trapezoidal, Triangular, Square

Pure and pulsating

Alternating and direct currents. The horizontal axis is time and the vertical axis represents voltage.


 

Origins of AC and DC current

A magnetic field near a 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 toward the positive side. This is how DC power from a battery was born, primarily attributed to Thomas Edison's work.

AC generators gradually replaced Edison's DC battery system because AC is safer to transfer over the longer city distances and can provide more power. Instead of applying the magnetism along the wire steadily, scientist Nikola Tesla used a magnet that was rotating. 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.

Use of transformers with Alternating Current (AC)

Another difference between AC and DC involves the amount of energy it can carry. Each battery is designed to produce only one voltage, and that voltage of DC cannot travel very far until it begins to lose energy. But AC's voltage from a generator, in a power plant, can be bumped up or down in strength by another mechanism called a transformer. Transformers are located on the electrical pole on the street, not at the power plant. They change very high voltage into a lower voltage appropriate for your home appliances, like lamps and refrigerators.

Storage and conversion from AC to DC and vice versa

AC can even be changed to DC by an adaptor that you might use to power the battery on your laptop. DC can be "bumped" up or down, it is just a little more difficult. Inverters change DC to AC. For example, for your car an inverter would change the 12 volt DC to 120 Volt AC to run a small device. While DC can be stored in batteries, you cannot store AC.

 


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