Electrical Definitions


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Electrical Definitions

Letter - F


The unit of measure for capacitance. It is the capacitance of a capacitor in which an applied voltage of one volt will store a charge of one coulomb. The more practical units of capacitance are the microfarad and picofarad.



All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device.



Resonance resulting when the iron core of an inductive component of an LC circuit is saturated, increasing the inductive reactance with respect to the capacitance reactance.


Festoon Lighting

A string of outdoor lights that is suspended between two points.



A term commonly used to describe the stationary (Stator) member of a DC Motor. The field provides the magnetic field with which the mechanically rotating (Armature or Rotor) member interacts.



In a directly heated electron tube, a heating element which also serves as the emitter.



An accessory such as a locknut, bushing, or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function.



Flashing due to high current flowing between two points of different potential. Usually due to insulation breakdown resulting from arcing.



A surge or sag in voltage amplitude, often caused by load switching or fault clearing.



The magnetic field which is established around an energized conductor or permanent magnet. The field is represented by flux lines creating a flux pattern between opposite poles. The density of the flux lines is a measure of the strength of the magnetic field.


Form Factor

The ratio of the r.m.s. to the average value of a periodic wave.


Forward Transfer Impedance

The amount of impedance placed between the source and load with installation of a power conditioner. With no power conditioner, the full utility power is delivered to the load; even a transformer adds some opposition to the transfer of power. On transformer based power conditioners, a high forward transfer impedance limits the amount of inrush current available to the load.



The rate at which alternating current makes a complete cycle of reversals. It is expressed in cycles per second. In the U.S. 60 cycles (Hz) is the standard while in other countries 50 Hz (cycles) is more common. The frequency of the AC will affect the speed of a motor


Full Load Current

The current flowing through the line when the motor is operating at full-load torque and full-load speed with rated frequency and voltage applied to the motor terminals.


Full Load Torque

That torque of a motor necessary to produce its rated horsepower at full-load speed, sometimes referred to as running torque.



An overcurrent protective device with a circuit opening fusible part that is heated and severed by the passage of overcurrent
through it.