Beatrice Lang
Alternating current (AC) is a type of electric current that periodically changes direction and voltage magnitude. It is the standard electricity that comes out of power outlets and is used to power most homes and offices. AC is generated by spinning a wire loop inside a magnetic field, which induces a current along the wire. This wire loop can be spun using various methods, such as wind, steam, or flowing water turbines. The direction of the current in AC constantly switches between positive and negative, causing electromagnetic waves and a phenomenon called skin effect. AC has the advantage of being able to transmit power over long distances efficiently due to its ability to easily convert voltage levels using transformers.
Characteristics and Values of Alternating Current (AC)
| Characteristics | Values |
|---|---|
| Type of Current | Electric current that periodically reverses direction |
| Flow of Electric Charge | Changes direction from positive to negative |
| Electric Conductors | Not conducive to electromagnetic waves |
| Direction of Current | Constantly changing |
| Power Transmission | Over long distances |
| Power Loss | Less energy loss during transmission |
| Voltage | Alternates |
| Current | Alternates |
| Power Sources | Power plants, generators, or outlets |
| Applications | Household appliances, electric motors, long-distance power transmission |
| Waveform | Sine wave |
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What You'll Learn
Alternating current (AC) vs. Direct Current (DC)
Electric current can flow in two ways: direct current (DC) and alternating current (AC). These terms describe the types of current flow in a circuit.
Direct current is a method in which electricity always flows in a certain direction, similar to the flow of a river. It refers to the flow of electricity obtained from batteries, solar cells, and fuel cells. The voltage is always constant, and the current flows in a single direction. DC is defined as the "unidirectional" flow of current. Voltage and current can vary over time, as long as the direction of the flow does not change. DC is used to supply power to electrical devices and charge batteries. For example, flashlights, mobile phone batteries, flat-screen TVs, and electric vehicles run on DC.
Alternating current, on the other hand, is a method in which the positive and negative sides are constantly switched, and the direction of the flow of electricity changes accordingly. This is the type of current obtained from a generator or outlet. The voltage periodically changes from positive to negative and vice versa, and the direction of the current also changes periodically. In AC, not all the electricity passes through the load, and some power is generated just by travelling back and forth between the load and the power source. This is called reactive power. AC is easier to transform between voltage levels, which makes high-voltage transmission more feasible. It is the standard electricity that comes out of power outlets and is used to power household appliances, offices, and buildings. AC can also power electric motors, which is useful for large appliances like dishwashers and refrigerators.
AC was first tested in 1832, based on the principles of Michael Faraday, through the use of a Dynamo Electric Generator. In the late 1880s, a battle between alternating and direct current distribution took place, with Thomas Edison constructing 121 DC power stations in the United States by 1887, and Ganz Works electrifying all of Rome with AC in 1886. AC was eventually chosen as the primary means to transmit electricity over long distances.
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How AC is produced using an alternator
Alternating Current (AC) is a type of electric current that periodically changes direction and continuously varies in magnitude over time. It is the standard electricity supplied to homes and businesses and is used to power household appliances like kitchen appliances, televisions, fans, and electric lamps. AC is advantageous for long-distance power transmission as it can be converted to and from high voltages easily using transformers, resulting in lower energy loss during transmission. Additionally, AC can travel farther than direct current (DC) and can convert voltage levels with a single component (a transformer).
AC can be produced using a device called an alternator, which is a type of electrical generator specifically designed to generate alternating current. The basic principle behind an alternator is spinning a wire loop, known as the rotor, inside a magnetic field. This rotating magnetic field induces an AC voltage in the wire coils surrounding a fixed iron core, known as the stator. The rotor's magnetic field can be produced by permanent magnets or by a field coil electromagnet.
There are different types of alternators, including linear alternators, rotating armatures with stationary magnetic fields, and wound field coils that form an electromagnet to produce the rotating magnetic field. The type of alternator used depends on the application and specific requirements. Large 50 or 60 Hz three-phase alternators in power plants generate most of the world's electric power.
Automotive alternators, commonly found in vehicles, use a rotor winding that allows control of the generated voltage by varying the current in the rotor field winding. The voltage and current in automotive alternators are regulated by an automatic voltage control device to maintain a constant output voltage. Additionally, automotive alternators use diodes to convert the generated AC power to DC power, as car batteries require DC power.
Alternators have been used since the late 1870s, with pioneers such as Michael Faraday, Hippolyte Pixii, Lord Kelvin, and Sebastian Ferranti developing early alternators. The introduction of large-scale electrical systems with central generation stations in the late 1870s marked the beginning of AC power generation for applications such as street lighting. The first hydroelectric alternating current power plant, the Ames Hydroelectric Generating Plant, was constructed in 1890, demonstrating the early adoption of AC power generation.
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How AC is transmitted over long distances
Alternating Current (AC) is a type of electric current that periodically changes direction and magnitude continuously with time. The electric charge in AC changes direction and the voltage reverses because of the changing direction of the current. This is in contrast to Direct Current (DC), which only flows in one direction and is produced by sources such as batteries, solar cells, and fuel cells.
AC is the standard form of electricity that is delivered to residences and businesses and is used by plugging appliances into wall sockets. It is also used to power electric motors. AC is generated by spinning a wire loop inside a magnetic field, which induces a current along the wire. This wire loop can be spun using various means, including wind, steam, or flowing water turbines.
AC can be transmitted over long distances relatively easily, especially at high voltages (over 110kV). Higher voltages result in lower currents, which generate less heat in the power lines due to resistance. This makes AC suitable for long-distance power transmission. Additionally, AC can be easily converted to and from high voltages using transformers, making it convenient for long-distance transmission.
The use of AC for long-distance power transmission has a long history, with early hydroelectric AC power plants constructed as early as 1890. These plants transmitted single-phase electricity over long distances for street lighting and other applications. The first three-phase system was established in Frankfurt, Germany, in 1891.
While AC is generally preferred for long-distance transmission, there are some cases where DC transmission may be more advantageous. For very long transmission lines, undersea cables, or transmissions between non-synchronised grids, the use of high-voltage DC may be more justified due to reduced losses and improved efficiency.
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The difference between AC and DC power
Alternating Current (AC) and Direct Current (DC) are two types of current flow in a circuit. AC is the standard electricity that comes out of power outlets and is delivered directly to businesses and residences. It is characterised by its periodically changing direction and strength of flow, typically following a sinusoidal waveform. The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with the positive direction of the current and vice versa. The current flow changes between positive and negative because of electrons, which can move in either a positive (upward) or negative (downward) direction. This is known as the sinusoidal AC wave.
AC is produced using a device called an alternator, which is a special type of electrical generator. A loop of wire is spun inside a magnetic field, which induces a current along the wire. The rotation of the wire can come from any number of means, such as a wind turbine, a steam turbine, or flowing water. Because the wire spins and enters a area of different magnetic polarity periodically, the voltage and current alternate on the wire. AC can be converted to and from high voltages easily using transformers.
Direct Current (DC), on the other hand, is a linear electrical current that moves in only one direction. It is commonly used in batteries, solar cells, and other electronic devices such as computers or mobile phones. DC power is far more consistent in terms of voltage delivery, meaning that most electronics that require a constant voltage, such as smartphones, computers, and automotive systems, rely on it and use DC power sources such as batteries. DC power can also be "made" from AC power by using a rectifier that converts AC to DC.
The main difference between AC and DC power is the direction in which the electrons flow. This distinction leads to all other differences between these types of electricity. AC power can travel farther than DC power, a huge advantage when it comes to delivering power to consumers via power outlets. However, DC power is more stable and consistent, making it suitable for devices that require a constant voltage.
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The advantages of AC over DC
Alternating Current (AC) is a type of current flow in a circuit where the electric charge changes direction periodically and reverses voltage. It is the standard electricity that comes out of power outlets. Direct Current (DC), on the other hand, is a linear electrical current that moves in only one direction and provides a constant voltage or current.
There are several advantages of AC over DC. Firstly, AC can be easily converted to and from high voltages using transformers, which results in lower resistance in the wires and more efficient long-distance power transmission. This makes AC the primary means to transmit electricity over long distances. In contrast, DC power is difficult and costly to convert to high voltages and requires complicated circuits.
Secondly, AC is simpler to operate through the usage of wires and transformers for voltage adjustments. It is also more suitable for powering electric motors, which are the same devices as generators, except that they convert electrical energy into mechanical energy.
Thirdly, AC is more suitable for certain applications such as powering large appliances like refrigerators, dishwashers, washing machines, and refrigerators, which run on AC.
Lastly, AC is more dominant in most power systems worldwide, which makes it more accessible and widely used.
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Frequently asked questions
Alternating current (AC) is a type of current flow in a circuit where the electric charge changes direction periodically.
In alternating current, the positive and negative sides are constantly switched, and the direction of the flow of electricity changes accordingly. The voltage also periodically changes from positive to negative and vice versa.
Alternating current is produced using a device called an alternator, which is a type of electrical generator. A loop of wire is spun inside a magnetic field, which induces a current along the wire. The wire moves into areas of different magnetic polarity, causing the voltage and current to alternate.
Direct current (DC) is a linear electrical current that moves in only one direction. In contrast, alternating current switches direction periodically.
Alternating current is the standard electricity that comes out of power outlets and is used to power most homes and offices. It is also used to power large appliances such as refrigerators and dishwashers.
