Basic Electrical Terms

Alternating Current (AC).     
- An electric current that reverses its direction many times a second at regular intervals.

Ambient Temperature
- It refers to the surrounding temperature to where an electrical installation is based.

Ammeter
- An instrument for measuring the flow of electrical current in amperes. Ammeters are always connected in series with the circuit to be tested.

Ampacity
- The maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration.

Ampere (A)
- A unit of measure for the intensity of an electric current flowing in a circuit. One ampere is equal to a current flow of one coulomb per second.

Ampere-Hour (Ah)
- A unit of measure for battery capacity. It is obtained by multiplying the current (in
amperes) by the time (in hours) during which current flows. For example, a battery which provides 5 amperes for 20 hours is said to deliver 100 ampere - hours.

Anchor
- Auxiliary fastener for securely holding a nail, screw or bolt.

Apparent Power
- Measured in volt-amperes (VA). Apparent power is the product of the rms voltage and the rms current.

Armature
- The movable part of a generator or motor. It is made up of conductors which rotate through a magnetic field to provide voltage or force by electromagnetic induction. The pivoted points in generator regulators are also called armatures.

Capacitance
- The ability of a body to store an electrical charge. Measured in farads as the ratio of the electric charge of the object (Q, measured in coulombs) to the voltage across the object (V, measured in volts).

Capacitor
- A device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator.(ie. a bucket of charge)
- Commonly used for filtering out voltage spikes.

Circuit
- A closed path in which electrons from a
voltage or current source flow. Circuits can be in series, parallel, or in any combination of the two.

Circuit Breaker
- An automatic device for stopping the flow of current in an electric circuit. To restore service, the circuit breaker must be reset (closed) after correcting the cause of the overload or failure. Circuit breakers are used in conjunction with protective relays to protect circuits from faults.

Conductor
- Any material through which electric current can flow freely. Conductive materials, such as metals, have a relatively low resistance. Copper and aluminum wire are the most common conductors.

Cord
- Especially flexible wire. Allows mobile devices to be connected to the network.

Corona
- A corona discharge is an electrical discharge brought on by the ionization of a fluid such as air surrounding a conductor that is electrically charged. Spontaneous corona discharges occur naturally in high-voltage systems unless care is taken to limit the electric field strength.

C.N.E
- The abbreviation stands for Combined Neutral & Earth.

C.P.C
- The abbreviation stands for Circuit Protective Conductor.

Current limitation.    
- It when a resistor is placed in series with an electronic component so that the current passing through the component is limited based on the value of the resistor connected.

Cycle
- The change in an alternating electrical sine wave from zero to a positive peak to zero to a negative peak and back to zero.

Demand
- The average value of power or related quantity over a specified period of time.

Dielectric constant
- A quantity measuring the ability of a substance to store electrical energy in an
electric field.

Dielectric strength
- The maximum electric field that a pure material can withstand under ideal conditions without breaking down.

Diode
- A semiconductor device with two terminals, typically allowing the flow of current in one direction only. Diodes allow current to flow when the anode is positive in relation to the cathode.

Direct Current (DC)
- Electric current that flows in only one direction.

Discrimination
- It is the ability of an over-current protective device to break the supply of the circuit in which a fault has developed without affecting other electrical circuits in the same system.

Dowel
- An accessory fastener into which a screw or nail is driven.

Electric current
- The flow of an electric charge through a conductor. An electric current can be
likened to the flow of water in a pipe.
- Measured in amperes.

Electrical substation
- A substation is a part of an electrical generation, transmission, and distribution
system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions.
- Between the generating station and consumer, electric power may flow through several substations at different voltage levels. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.

Electrolyte
- Any substance which, in solution, is dissociated into ions and is thus made
capable of conducting an electrical current.
- The sulfuric acid water solution in a storage battery is an electrolyte.

Electromotive Force
- A difference in potential that tends to give rise to an electric current. Measured in volts.

Electron
- A tiny particle which rotates around the nucleus of an atom.
- It has a negative charge of electricity.

Electron theory
- The theory which explains the nature of electricity and the exchange of "free"
electrons between atoms of a conductor.
- It is also used as one theory to explain direction of current flow in a circuit.

Extension
- A piece of flexible wire fitted with a plug and socket.

Farad
- A unit of measure for capacitance.
- One farad is equal to one coulomb per volt.

Ferro resonance
- A type of resonance in electric circuits
which occurs when a circuit containing a non-linear inductance is fed from a source that has series capacitance, and the circuit is subjected to a disturbance such as opening of a switch.
- It can cause over voltages and over currents in an electrical power system and can pose a risk to transmission and distribution equipment and to operational personnel.

Frequency
- The number of cycles per second, measured in Hertz.
- If a current completes one cycle per second, then the frequency is 1 Hz; 60 cycles per second equals 60 Hz.

Filtering application
- Capacitor can be used to smooth out pulsating DC from a rectifier, by bypassing AC components to ground.

Filter circuits
- A resistor could be used to attenuate a signal.

Fuse
- A circuit interrupting device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.
- To restore service, the fuse must be replaced using a similar fuse with the same size and rating after correcting the cause of failure.

Generator
- A device which converts mechanical energy into electrical energy.

Ground
- The reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.

Ground Fault Circuit Interrupters (GFCI)
- A device intended for the protection of
personnel that functions to de-energize
circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the over current protective device of the supply circuit.

Grouping Factor
- It is a factor which is applied to the number of cables to which the cable is to be installed with.

Henry
- A unit of measure for inductance. If the rate of change of current in a circuit is one ampere per second and the resulting electromotive.
- force is one volt, then the inductance of the circuit is one henry.

Hertz
- A unit of measure for frequency.

Replacing
- the earlier term of cycle per second (cps).

Impedance
- It's a measure of the opposition that a circuit presents to a current when a voltage is applied.
- Impedance extends the concept of resistance to AC circuits, and possesses
both magnitude and phase, unlike resistance, which has only magnitude.

Inductance
- The property of a conductor by which a change in current flowing through it induces (creates) a voltage (electromotive force) in both the conductor itself (self-inductance) and in any nearby conductors (mutual inductance). Measured in henry (H).

Inductor
- A coil of wire wrapped around an iron core.
- The inductance is directly proportional to the number of turns in the coil.
Insulator
- Any material where electric current does not flow freely. Insulative materials, such as glass, rubber, air, and many plastics have a relatively high resistance.
- Insulators protect equipment and life from electric shock.

Inverter
- An apparatus that converts direct current into alternating current.
- Kilowatt (kW) = 1000 watts.
- Kilowatt-hour (kWhh)
- The product of power in kW and time in hours. Equal to 1000 Watt-hours. For example, if a 100W light bulb is used for 4 hours 0.4kWhs of energy will be used (100W x 1kW/ 1000 Watts x 4 hours). Electrical energy is sold in units of kWh.

Kilowatt-hour Meter
- A device used to measure electrical energy use.

Linear attenuation.  
- A resistor could be used to attenuate a signal.

Load
- Anything which consumes electrical energy, such as lights, transformers, heaters and electric motors.

Load Rejection
- The condition in which there is a sudden
load loss in the system which causes the
generating equipment to be over-frequency.
- A load rejection test confirms that the system can withstand a sudden loss of load and return to normal operating conditions using its governor. Load banks are normally used for these tests as part of the commissioning process for electrical power systems.

Maximum Demand
- It is the amount of current which is drawn by the circuit after considering the amount of load. It is obtained after totalling the total power.

Mutual Induction
- Occurs when changing current in one coil induces voltage in a second coil.

Ohm
- A unit of measure of resistance. One ohm is equivalent to the resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt.

Ohms Law
- The mathematical equation that explains the relationship between current, voltage, and resistance (V=IR).

Ohmmeter
- An instrument for measuring the resistance in ohms of an electrical circuit.

Open Circuit
- It occurs when a circuit is broken, such as by a broken wire or open switch, interrupting the flow of current through the circuit. It is analogous to a closed valve in a water system.

Parallel Circuit
- A circuit in which there are multiple paths for electricity to flow. Each load connected in a separate path receives the full circuit voltage, and the total circuit current is equal to the sum of the individual branch currents.

P.E.N
- The abbreviation stands for Protective Earth & Neutral.

Piezoelectricity
- Electric polarization in a substance (especially certain crystals) resulting from the application of mechanical stress (pressure).

Plumb Line
- A tool used in electrical installations to tunnel routes for conduits in walls.

P.M.E
- The abbreviation stands for Protective Multiple Earthing.

Polarity
- A collective term applied to the positive
(+) and negative ( -) ends of a magnet or
electrical mechanism such as a coil or battery.

Power
- It is the rate at which electrical energy is
transferred by an electric circuit.
- Measured in Watts.

Power Factor
- It is the ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage.
- The difference between the two is caused by reactance in the circuit and represents power that does no useful work.

Protective Relay
- A relay device designed to trip a circuit
breaker when a fault is detected.

RC timing circuit.
- A resistor could be connected in series with a capacitor to create an RC circuit, which can be used as a timer, as would be seen later.

Reactive Power
- The portion of electricity that establishes and sustains the electric and magnetic fields of AC equipment. Exists in an AC circuit when the current and voltage are not in phase.
- Measured in VARS.

Rectifier
- It is an electrical device that converts an alternating current to a direct one by allowing a current to flow through it in one direction only.

Relay
- An electrical coil switch that uses a small current to control a much larger current.

Reluctance
- The resistance that a magnetic circuit offers to lines of force in a magnetic field.

Residual-current device (RCD)
- A protective device that compares the strength of the electric current in the phase and neutral wires of the circuit. In the event of a current leak the RCD very quickly opens the network.

Resistance
- The opposition to the passage of an electric current. Electrical resistance can be compared to the friction experienced by water when flowing through a pipe.
- Measured in ohms.

Resistor
- It is a device usually made of wire or carbon which presents a resistance to current flow.

Rotor
- It is the rotating part of an electrical machine such as a generator, motor, or alternator.

Self Induction
- It refers to voltage which occurs in a coil when there is a change of current.

Semiconductor
- A solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects.
- Devices made of semiconductors, notably silicon, are essential components of most electronic circuits.

Series Circuit
- It is a circuit in which there is only one path for electricity to flow.
- All of the current in the circuit must flow through all of the loads.

Series-Parallel Circuit
- It is a circuit in which some of the circuit components are connected in series and the others are connected in parallel.

Service
- It is the conductors and equipment used to deliver energy from the electrical supply
system to the system being served.

Short Circuit
- This when one part of an electric circuit comes in contact with another part of the same circuit, diverting the flow of current from its desired path.

Solid State Circuit
- This refers to Electronic (integrated) circuits which utilize diodes and silicon controlled rectifiers.

Strap
- It is a thin layer of mortar to smooth the concrete surface.

Thermal Insulation
- It is an electrical factor which is considered where a cable is semi or totally enclosed in insulating material.This factor is usually considered when the cable is installed.

Transformer
- It is an electrical apparatus designed to convert alternating current from one voltage to another. It can be designed specifically to step up or step down voltages. The transformer uses the magnetic induction principle. It has no moving parts and is therefore a completely stationary solid state device which promises a long trouble free life provided it operates under required conditions. A basic transformer has 2 or more cores of insulated wire.

Transistors
- It is a semiconductor device with three connections, capable of amplification in
addition to rectification.

True Power
- The power manifested in tangible form such as electromagnetic radiation, acoustic waves, or mechanical phenomena.
- In a direct current (DC) circuit, or in an alternating current (AC) circuit whose impedance is a pure resistance, the voltage and current are in phase.
- It is measured in watts.

Tuning
- Air capacitor is used in tuning circuits eg radio.

VARS
- This is a unit of measure of reactive power.
- Vars may be considered as either the imaginary part of apparent power, or the power flowing into a reactive load, where voltage and current are specified in volts and amperes.

Variable Resistor
- This is a resistor that can be adjusted to different ranges of value.

Volt (V)
- It is a unit measure of voltage. One volt is equal to the difference of potential that would drive one ampere of current against one ohm of resistance.

Volt-Ampere (VA)
- It is a unit of measure of apparent power. - It is the product of the rms voltage and the rms current.

Voltage
-It is an electromotive force or "pressure"
that causes electrons to flow and can be
compared to water pressure which causes water to flow in a pipe.
- It is measured in volts.

Voltage divider.           
- This is a combination of two or more resistors connected in series to ground a tap between any point between the resistors is taken as the output voltage, the output voltage is less than the voltage across the resistors, a voltage divider is commonly used to bias an amplifier as would be seen later.

Voltage Drop
- It refers to the amount of voltage which is dropped due to the resistance of a conductor. This usually depends on length and cable size.

Voltmeter
- This is an instrument for measuring the force in volts of an electrical current. This is the difference of potential (voltage) between different points in an electrical circuit.
- Voltmeters have a high internal resistance are connected across (parallel to) the points where voltage is to be measured.

Watt (W)
- It is a unit of electrical power. One watt
is equivalent to one joule per second, corresponding to the power in an electric
circuit in which the potential difference is one volt and the current one ampere.

Watt-hour (Wh)
- This is a unit of electrical energy equivalent to a power consumption of one watt for one hour.

Wattmeter
- The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit.

Waveform
- A graphical representation of electrical cycles which shows the amount of variation in amplitude over some period of time.

Wire or cable core
- It is an insulated conductor designed to carry electrical current. Consists of one or more wires.

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