100!!! ELECTRICAL QUESTION & ANSWERS!!!

Electric Current

Electric Current, symbolized by I, is the quantitative measure of the flow rate of electric charge carriers. It is measured by determining the number of coulombs of charge that pass a specific point in the period of time. The unit of electric current is the Ampere.

The rate at which electrons flow through a circuit is defined as the current. If an electric circuit is likened to water flowing through a system of pipes, the current is analogous to the rate at which the water is flowing. Electric current is measured in amps.

Formal Definition of Electric Charge

The fundamental unit of charge is denoted: ±q 

It is the charge associated with a single electron or proton and is equal in magnitude to 1.60 x 10^-19 Coulombs. 

The Coulomb, denoted by C, is the basic unit of electrical charge. 

Charge can be either positive or negative 

One Coulomb = approximately 6.24 x 10^18unpaired electrons or unpaired protons. 

 To characterize electrical charge behavior we must start at the atom which consist of
1.Proton(s):positive charges
2.Neutron(s):neutral charges
3.Electron(s):negative charges 

Charge properties
1.Like charges repel one another
2.Unlike charges attract one another
3.The force of repulsion or attraction obeys the inverse square law  

Energy (J )

Energy in a system is measured by the amount of work which a system is capable of doing. The joule is the work done when the point of application of a force of one newton is displaced a distance of one meter in the direction of the force.

Power (W) 

It is the time rate of transferring or transforming energy. The watt is the power which gives rise to the production of energy at the rate of one joule per second.

Conductor

A material that allows for the easy establishment of a current with a minimal applied voltage

Examples: Silver, Copper, Aluminum, and most other metals

Insulator

A material that restricts the flow of current. Large potential differences are required to push electrical current through these materials.

Examples: Wood, Rubber, Plastic, and Glass.

Semiconductor 

A material that is usually viewed as a poor conductor, but under special circumstances it can be a useful conductor. 

Examples: Silicon and Germanium

Superconductor

A material that is capable of conducting electrical current with no resistance when placed below a certain temperature. This means that electrical currents can exist without the presence of an electric field.

Examples: Mercury below 4.15K and barium-yttrium copper-oxide below 92K K = Kelvin

Voltage, Volts

The measure of electrical pressure in a circuit. One volt of pressure is required to push one amp of current through a conductor with one ohm of resistance.

Voltage Spike

A sudden, extreme surge in voltage. A voltage spike can be caused by lightning striking near a power line, or the activation and deactivation of large equipment loads, such as air conditioners and elevators, in an office setting. Surge protectors are specified to control voltage spikes and protect equipment from damage.

 

Potential Difference or Electromotive Force (V, E, emf) 

The volt is the difference of electric potential between two points of a conductor carrying a constant current of one ampere, when the power dissipated between these points is equal to one watt.

Resistance (R, r) 

The ohm is the electrical resistance between two points of a conductor when a constant difference of potential of one volt, applied between these two points, produces in this conductor a current of one ampere, this conductor not being the source of any electromotive force.

Resistivity (r) 

The resistivity of a material is the dc resistance between the opposite parallel faces of a portion of the material having unit length and unit cross section.

Conductance (G, g) 

It is the electrical conductance of a conductor in which a current of one ampere is produced by an electric potential difference of one volt. One is the reciprocal of one ohm.

Conductivity (g) 

The conductivity of a material is the dc conductance between the opposite parallel faces of a portion of the material having unit length and unit cross section.

Capacitance (C) 

It is that property of a system of conductors and dielectrics which permits the storage of electricity when potential difference exists between the conductors. Its value is expressed as a ratio of a quantity of electricity to a potential difference. A capacitance value is always positive. The farad is the capacitance of a capacitor between the plates of which there appears a difference of potential of one volt when it is charged by a quantity of electricity equal to one coulomb.

Capacitor 

A multipurpose device that can store electrical charge in the form of an electric field. It is used, for example, for power factor correction in (inductive) AC circuits. Capacitors are used to buffer electricity (smooth out peaks) and to guard against momentary voltage losses in circuits (when changing batteries, for example).

Capacitor bank

A number of capacitors connected in parallel.

Circuit

A complete path for electrical current flowing from the building power source to the equipment being powered and back to the power source. 

Circuits are rated according to the number of amps they can accommodate. The total number of amps required by all of the equipment in a furniture installation will dictate the number of circuits required.
 

Circuit breaker

Devices that interrupt high currents to protect electrical equipment from damage caused by current surges, eg, from a short circuit or a lightning strike. (On a much smaller scale, they are used as an alternative to fuses in the home.) Circuit breakers are typically classified according to the medium they use to inhibit arc formation between the open contacts of the breaker. Media used include air, sulfur hexafluoride gas, oil and a vacuum.

Co-generation

A particularly efficient method of electricity generation that diverts heat, produced as a byproduct of the power generation process, to domestic and industrial heating systems. The heat is produced by combustion of fuel in the power station to create the steam that drives the generating turbines. It would otherwise be released to the atmosphere.

Converter

An electrical device, comprising a rectifier and inverter, used to alter the voltage and frequency of incoming alternating current in an electrical system. The term may also refer to inverters, rectifiers or frequency converters.

Distributed generation: 

This term refers to electricity generating installations that are scattered across the grid rather than placed at a central location. They tend to be small-scale generating plants – often operating using renewable fuels. They also include domestic power generators such as roof-top wind turbines and solar.

Ballast

A device in fluorescent lamps that regulates the level (amps) of electrical current and voltage flowing through the fluorescent lamp tube. Ballasts may be magnetic or electronic, with electronic being slightly more energy efficient.

Ground Conductor

The conductor of a circuit that provides safety from fire and electrical shock in cases of short circuits and other electrical problems. The conductor is physically attached to the earth and represents a zero volt potential, thus reducing the shock hazard to persons if an electrical device ever fails or short-circuits.

Hot Conductor

The conductor that carries current from the power source to the equipment. For a complete circuit, the hot conductor requires a neutral conductor to carry the current back to the power source.

Harmonic Currents, Harmonics

A distortion in electrical current caused by equipment that uses power in sharp pulses instead of in a smooth pattern. When electrical circuits share a common neutral conductor, harmonic currents can lead to an electrical overload, causing the neutral conductor to overheat.

Isolated Ground

Serves the same safety and protection function as a common ground conductor, but it is run in a separate “isolated” conductor. This separation usually — but not always — enables the isolated ground to reduce the amount of electrical noise that’s introduced into an electrical circuit. Therefore, computers, Uninterruptible Power Supplies, and other electronic equipment are often connected to an isolated ground. More than one hot/neutral conductor combination may share an isolated ground and still maintain a lower level of electrical noise versus common ground usage.

Junction Box

  

An electrical construction box that provides a space for the connection or “splicing” of the electrical conductors. Connections inside the junction box are usually accomplished with twist-on electrical conductors, called wire nuts.

Load

Describes the amount of power (amps) consumed by an electrical circuit or device. Loads are usually expressed in amps, but sometimes in watts.

Maximum Continuous Load

The maximum electrical current in a circuit expected to be in constant use for three hours or more. For safety considerations, a continuous load must not exceed 80% of the maximum electrical rating

Neutral Conductor

The conductor that carries current back to the power source. It is always used with a hot conductor to complete a circuit. (See Separate Neutral, Shared Neutral.)

Ohm

  

Ohm is the measure of electrical resistance, or impedance, in a circuit. One volt will cause one amp to flow through one ohm of resistance.

Open Circuit

  

A condition where the current flow through a conductor is interrupted by a missing or damaged component.

Short Circuit

  

A condition in which the hot conductor comes in contact with the ground or neutral conductor. A short circuit creates a spark or arc that often damages one or both of the circuit components and causes the circuit breaker to trip.

Surge Protector, Spike Protector

An electrical device that protects equipment from a sudden, high fluctuation in the level of voltage normally flowing during a period of time.

Three-Phase Power

  

A type of electrical system or circuit that utilizes three separate sources of alternating current. The three sources are electrically related to each other by a 120° phase separation. 

Relative Permittivity or Dielectric Constant

It is the ratio of electrostatic energy stored per unit volume of a dielectric for a unit potential gradient to the permittivity of a vacuum. The relative permittivity is a number.