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Armature

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One of the two principal electrical components of an electromechanical machine, generally in a motor or generator. It may also mean the pole piece of a permanent magnet or electromagnet or the moving iron part of a solenoid or relay.

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Commutator

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A rotary electrical switch in certain types of electric motors or electrical generators that periodically reverses the current direction between the rotor and the external circuit. It applies power to the best location on the rotor in a motor and picks off power similarly in a generator.

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Current

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A flow of electric charge through a conductive medium. In electric circuits, this charge is often carried by moving electrons in a wire. The SI unit for measuring the rate of flow of electric charge is the ampere.

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Electromagnet

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A type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off.

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Electromotive Force (EMF)

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Refers to voltage generated by a battery or by the magnetic force according to Faraday’s Law, which states that a time varying magnetic field will induce an electric current. Measured in volts.

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Horsepower (hp)

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The name of several units of measurement of power, the rate at which work is done. The most common conversion factor is 1 hp = 746 watts. The term was adopted by James Watt to compare the output of steam engines with the power of draft horses.

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Ohm's Law

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States that the current through a conductor between two points is directly proportional to the potential difference across the two points.

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Resistance

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The opposition to the passage of an electric current through an element. The SI unit of electrical resistance is the ohm (Ω).

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Stator

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The stationary part of a rotor system or a siren, found in an electric generator, electric motor, siren, or biological rotors.

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Torque

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The tendency of a force to rotate an object about an axis, fulcrum, or pivot. Mathematically, torque is defined as the cross product of force and the lever-arm distance, which tends to produce rotation.