A rheostat is an electrical component that has an adjustable resistance. It is a type of potentiometer that has two terminals instead of three. The two main types of rheostat are the rotary and slider. The symbol for a rheostat is a resistor symbol with an arrow diagonally across it. They are used in many different applications, from light dimmers to the motor controllers in large industrial machines.
Rheostat Construction
Most rheostats are the wire-wound type that have a long length...
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A transformer transfers electrical energy between two circuits. It usually consists of two wire coils wrapped around a core. These coils are called primary and secondary windings. Energy is transferred by mutual induction caused by a changing electromagnetic field. If the coils have different number of turns around the core, the voltage induced in the secondary coil will be different to the first.
History of Transformers
Transformers are based on the theory of electromagnetic induction...
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A resistor restricts the flow of current. It is a basic component of all electrical devices, even the filament in a light globe is a resistor. Resistors are defined by their material type, resistance, power rating, and tolerance.
Resistor Types
There are four main types of resistor: carbon, film, wirewound, and semiconductor. Carbon resistors are tiny insulated cylinders of carbon and ceramic dust with a terminal at each end. They have colored bands to show their resistance and...
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Some materials have the ability to produce electricity when subjected to mechanical stress. This is called the piezoelectric effect. This stress can be caused by hitting or twisting the material just enough to deform its crystal lattice without fracturing it. The effect also works in the opposite way, with the material deforming slightly when a small electric current is applied. Piezoelectricity was discovered more than one hundred years ago and has many applications today. It is used in...
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The ampere, amp for short, is the standard unit of electrical current. It is defined as the current required to produce a certain force between two parallel and infinitely long wires separated by one meter.
According to Ohm's law, one ampere of current is produced when one volt of potential difference exists across a conductor with one ohm of resistance. One ampere is also equal to the flow of one coulomb of electric charge per second. History of the Amp
The ampere was defined at an...
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An oscillator is a circuit that creates a waveform output from a direct current input. The two main types of oscillator are harmonic and relaxation. The harmonic oscillators have smooth curved waveforms, while relaxation oscillators have waveforms with sharp changes.
How Oscillators Work
A basic oscillator is a capacitor and inductor connected together. As the capacitor discharges, the current creates a magnetic field in the inductor. When the capacitor is fully discharged, the field...
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A diode is a solid-state device that allows current to flow in only one direction, a process known as rectification. Diodes are a fundamental component of electrical circuits. They are also used to form other components, such as the bipolar transistor which uses two diodes in series.
History of the Diode
Thermionic rectifiers were discovered in 1873 by Frederick Guthrie, and later rediscovered by Thomas Edison in 1880, while crystal rectifiers were discovered in 1874 by Karl Braun. It...
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A laser diode is a small device that is similar in construction and appearance to a light emitting diode (LED). The main difference is that a laser diode produces coherent laser light while an LED produces incoherent light. Ever since they were first invented in 1962, millions of laser diodes have been used in a wide range of consumer and industrial products.
History
The first laser diode was invented by a team of researchers at General Electric in 1962 but many other research teams...
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A relay is a remote switch controlled by current, magnetism, or temperature. The relay was invented in 1835 by Joseph Henry (1979-1878), an American scientist. Relays are a common component in many devices, and there are many different types of relays.
Relay Types
The two main types of relay are electromechanical and solid-state. Electromechanical relays have a moving plate with contacts on it, while solid-state relays work similar to transistors and have no moving parts.
Power relays...
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An inductor is a conducting coil, wrapped around a core, that creates inductance when an alternating current flows through it. Inductors are used to impede the flow of current in a circuit. The conductor is usually thin magnet wire, and the core is usually air or steel.
Working of an Inductor
When the alternating current flows through an inductor, it creates an electromagnetic field. The strength of this field depends on number of coils, the coil diameter and the permeability of the...
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