Alternating Current

Alternating current (AC) is one of two forms of electrical current that flow in different directions depending on the charge of the circuit. Electrical current, the rate of electron flow between two points during a period of time, will flow toward the correspondingly charged point on the circuit. If one point of a circuit is positively charged (has more protons than electrons), the negatively charged atoms will constantly move toward that point of the circuit to balance the charge, causing a steady flow of electrons.

Alternating current’s direction of flow changes if the sides of the circuit are regularly flipped. Alternating current is steady; it’s typically pictured as a sinusoidal wave. In contrast, direct current never changes direction but always flows from one side of a circuit to another.

An alternator steadily rotates a magnetic field, and the positively and negatively charged sides are constantly changing location. Thus, the flow of current reverses regularly. Vehicles use alternators as a source of electrical power.

Benefits of alternating current

Alternating current is ideal for transmitting electricity across long distances. The high voltages, though changing direction regularly, propel current throughout the cables that run cross-country. Extremely high voltages also reduce energy loss; in electrical cables, very high voltages in the wire are designed to have low current. The lowered current makes it less likely that wires will overheat. Some electrical wires do use direct current as of recent years, but alternating current is more useful for quickly converting voltages so that optimal voltage is used for each wire and transmission.

Alternating current allows the use of transformers, which are systems that use electromagnetic techniques to transfer an alternating current between wires. Each circuit has a series of coils through which the alternating current passes. Based on the amount of coils in the second wire, the voltage increases or decreases. Extremely high voltages, the kinds that can transmit electrical current cross-country, aren’t safe for household use. Transformers lower voltage so that it is acceptable to enter a wall outlet, for instance. Then they increase the voltage for a transmission to leave the home and pass over long distances.

Electronics such as computers do require direct current to run, though, so they have methods of converting the incoming AC into DC. For instance, a power supply unit performs that job in a computer. An inconsistent current direction could damage electronic systems.



Jenna Phipps
Jenna Phipps is a contributor for websites such as and Enterprise Storage Forum. She writes about information technology security, networking, and data storage. Jenna lives in Nashville, TN.

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