A thorough understanding of basic electrical terms and definitions is required for a better understanding of electricity. In this post, we will cover some of the most commonly used basic electrical terms and definitions.

An electric current that changes direction at regular intervals many times per second. Alternating current, abbreviated AC, is the periodic reversal of electric charges. It begins at zero, grows to a maximum, decreases to zero, reverses, reaches a maximum in the opposite direction, returns to zero, and continues indefinitely.

An ammeter is a device that measures the flow of electrical current in amperes. It is always wired in series with the circuit. The magnitude of the current is measured using an ammeter. The ammeter has very low resistance, and the voltage drop across the ammeter is very low, so the measurement accuracy is unaffected.

The maximum amount of electric current that a conductor or device can carry before deterioration, either immediate or progressive.

A conductor’s ampacity is its ability to dissipate heat without causing damage to the conductor or its insulation. When the current flowing in the conductor exceeds its ampacity, the conductor and its insulation heat up. The conductor’s ampacity is determined by:

1. The temperature rating of the insulation,
2. The conductor material’s electrical resistance
3. The temperature outdoor,
4. The insulated conductor’s ability to dissipate heat to the surroundings.

The larger the diameter of the conductor, the greater the ampacity.

The unit of measurement for battery capacity is Ah. It is nothing more than multiplying the current (in amperes) by the time (in hours) that current flows. For example, consider a battery that can deliver 20 amps for 10 hours. The battery capacity is then 20 X 10 = 200 Ah.

The intensity of an electric current flowing in a circuit is measured in amperes (A). One ampere equals one coulomb per second of current flow. (I =Q/t) As a result, 1A = 1C/Sec.

The unit of measurement for electric current in a circuit is the ampere. The number of electrons passing through a circuit determines the ampere. The greater the number of electrons passing through an electric circuit, the greater the electric current flowing through the circuit. The flow of an electric current in a circuit equals the rate of electron flow (I=Q/t). To put it another way, 1A = 1C/Sec.

It is the flow of electrons through time, specifically 6.24 x 1018 electrons per second. Perhaps more importantly, one amp flows when a voltage of one volt is applied to a resistance of one ohm. That is the foundation of Ohm’s law. It is known as the electrical current measurement unit.

The product of a circuit’s voltage and current without regard for the phase angle is known as apparent power, and it is the product of reactive power and true power. The capital letter S represents apparent power, which is measured in Volt-Amps (VA).

A generator or motor’s movable component. It consists of conductors that rotate through a magnetic field to provide voltage or force through electromagnetic induction. Armatures are the pivoting points in generator regulators.

A rotor is the rotating component of a motor. It can have current-conducting bars, be wound, or simply be a rotor.

An armature is made up of current-conducting bars and brushes that provide an electrical path for the current. Slip rings provide an electrical path for the current in a wound rotor. A rotor may also contain permanent magnets or simply laminated bars that interact with the stator electromagnetically. When discussing DC motors, the armature is commonly used.

Capacitance is the ability of two metal plates that are close but not touching to hold an electrical charge given to them by being connected to an external EMF. This charge will be held by them until it is released into a load connected between them. The capacitance is measured in Farads and is proportional to the area shared by the plates and inversely proportional to their distance apart. It can be increased by sandwiching various insulators between them.

A capacitor is a two-terminal passive electrical component used to temporarily store electrical energy in an electric field. Practical capacitors come in a variety of shapes and sizes, but they all have at least two electrical conductors (plates) separated by a dielectric (i.e. an insulator that can store energy by becoming polarized).

A dielectric can be made of glass, ceramic, plastic film, air, vacuum, paper, mica, oxide layer, and other materials. Capacitors are widely used in many common electrical devices as components of electrical circuits. An ideal capacitor, unlike a resistor, does not dissipate energy. A capacitor, on the other hand, stores energy in the form of an electrostatic field between its plates.

In a nutshell, a device that consists of one or more pairs of conductors separated by an insulator is used to store an electric charge. It is commonly used to filter out voltage spikes.

A path through which electric current flows. Circuits can be connected in series, parallel, or any combination of the two.

A circuit breaker is a switching (ON/OFF/TRIP) device that is used:

1. To turn on and off the load
2. Under the fault condition, for interrupting the circuit

When the load is turned on or off, an arc is formed between the breaker’s contacts. The circuit breaker has a medium in which the contacts are made/broken to quench the arc. The circuit breaker can be of the minimum oil circuit breaker, air circuit breaker, SF6, or vacuum type.

Conductors are capable of carrying an electric charge known as current. The movement of charge in a material is referred to as current. A good conductor has a low resistance to current flow. If the resistance to current flow is very high, we have an insulator. Metal is a good conductor of current; however, some metals conduct current better than others. The most common conductors are copper and aluminium wire.

Air is not a perfect insulator, and it contains many free electrons and ions even under normal conditions. When an electric field intensity is established between the conductors, these ions and free electrons are subjected to a force. Ions and free electrons are accelerated and moved in the opposite direction as a result of this effect.

During their motion, the charged particles collide with one another as well as with the very slow-moving uncharged molecules. As a result, the number of charged particles continues to rise rapidly. This increases the conduction of air between the conductors, resulting in a breakdown. As a result, the arc forms between the conductors. This is referred to as the corona.

The rate at which electrons flow past a point in a complete electrical circuit is defined as current. At its most fundamental, current = flow. The international unit for measuring current is the ampere (or amp). It denotes the number of electrons (also known as “electrical charge”) that flow past a point in a circuit over a given time period.

The transition of an alternating electrical sine wave from zero to a positive peak, then back to zero.

The average value of energy over a specified period of time.

A measure of a substance’s ability to store electrical energy in an electric field.

The highest electric field that a pure material can withstand under ideal conditions without degrading (i.e., without experiencing failure of its insulating properties).

A semiconductor device with two terminals that typically allows current to flow in only one direction. When the anode is positive in relation to the cathode, current can flow.

 An electric current that flows in only one direction.

Any substance that, when dissociated into ions in solution, becomes capable of conducting an electrical current. The electrolyte in a storage battery is a sulfuric acid-water solution.

A potential difference that causes an electric current to flow. Voltage is measured in volts.

A tiny particle that revolves around an atom’s nucleus. It has a negative electrical charge.

The theory that describes the nature of electricity and the exchange of “free” electrons between conductor atoms. It is also one theory used to explain the direction of current flow in a circuit.

A capacitance unit of measurement. A farad equals one coulomb per volt.

A type of electric circuit resonance (nonlinear resonance) that occurs when a circuit with a nonlinear inductance is fed from a source with series capacitance and the circuit is subjected to a disturbance such as the opening of a switch. It can cause overvoltages and overcurrents in an electrical power system, putting transmission and distribution equipment as well as operational personnel at risk.

The frequency of cycles per second. Hertz is the measurement unit. The frequency of a current is 1 Hz if it completes one cycle per second; 60 cycles per second equals 60 Hz.

A circuit interrupter is a piece of wire that melts and breaks an electric circuit when the current exceeds a safe level. After repairing the cause of the failure, the fuse must be replaced with a similar fuse of the same size and rating to restore service.

 A device that converts mechanical energy into electrical energy.

 A voltage reference point in an electrical circuit, a common return path for electric current, or a direct physical connection to the Earth.

A device intended for personnel protection that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value less than that required to operate the supply circuit’s overcurrent protective device.

A unit of inductance measurement. If the current change rate in a circuit is one ampere per second and the resulting electromotive force is one volt, the circuit’s inductance is one henry.

A frequency unit of measurement. Taking the place of the earlier term cycle per second (cps).

The amount of resistance a circuit presents to a current when a voltage is applied. In contrast to resistance, which has only magnitude, impedance extends the concept of resistance to AC circuits and has both magnitude and phase.

A conductor property in which a change in current flowing through it induces (creates) a voltage (electromotive force) in both the conductor and any nearby conductors (mutual inductance). Henry (H) is the measurement unit.

A wire coil wrapped around an iron core. The inductance of a coil is proportional to the number of turns.

Any material in which an electric current cannot freely flow. Insulating materials with relatively high resistance include glass, rubber, air, and many plastics. Insulators protect people from electric shock.

An apparatus that converts direct current into alternating current.

Power in kW multiplied by time in hours. The same as 1000 Watt-hours. For example, if a 100W light bulb is used for 4 hours, it will consume 0.4kWh of energy (100W x 1kW / 1000 Watts x 4 hours). Electrical energy is sold in kWh units.

A device used to measure the usage of electrical energy on premises.

Equal to 1000 watts.

Anything which consumes electrical energy, such as lights, transformers, electronic devices, and electric motors.

The condition in which there is a sudden loss of load in the system, causing the generating equipment to run at an excessive frequency. A load rejection test verifies that the system can withstand a sudden loss of load and resume normal operation using its governor. Load banks are typically used for these tests as part of the electrical power system commissioning process.

A flash of light caused by an electrical discharge in the atmosphere between two clouds or between a cloud and the earth.

A device that safeguards an electrical component against overvoltage.

Occurs when changing the current in one coil causes a voltage to be generated in a second coil.

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

The equation that explains the relationship between current, voltage, and resistance where it is represented as V=IR.

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

When a circuit is broken, such as by a broken wire or an open switch, the flow of current through the circuit is interrupted. It’s similar to a closed valve in a water system.

A circuit in which electricity can flow through multiple paths. The full circuit voltage is applied to each load connected in a separate path, and the total circuit current is equal to the sum of the individual branch currents.

Electric polarisation in a substance (particularly certain crystals) caused by mechanical stress or pressure.

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

The rate at which an electric circuit transfers electrical energy. Watts are units of measurement.

The ratio of the actual electrical power dissipated by an AC circuit to the product of current and voltage r.m.s. values. The difference between the two is caused by reactance in the circuit and represents power that is wasted.

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

The portion of electricity that creates and maintains the electric and magnetic fields of alternating current equipment. When the current and voltage in an alternating current circuit are not in phase. VARS are units of measurement.

 An electrical device that converts alternating current to direct current by allowing current to flow in only one direction.

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

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

The act of opposing the passage of an electric current. Electrical resistance is analogous to the friction that water experiences when flowing through a pipe. Ohms are units of measurement.

A device usually made of wire or carbon. The resistor opposes the flow of electric current.

 The rotating part of an electrical machine such as a generator, motor, or alternator.

The change in electric current cause induced voltage in an inductor.

Because of the addition of an impurity or temperature effects, a solid substance with conductivity between that of an insulator and that of most metals. Semiconductors, particularly silicon, are essential components of most electronic circuits.

 A circuit in which some circuit components are linked in series while others are linked in parallel.

A circuit with only one path for electricity to flow through. The circuit’s current must flow through all of the loads.

The conductors and equipment used to transport energy from the power supply system to the system being served.

When one part of an electric circuit makes contact with another part of the same circuit, the flow of current is diverted from its intended path.

Electronic (integrated) circuits that use semiconductor devices such as transistors, diodes, and silicon-controlled rectifiers are referred to as circuits.

A semiconductor device with three connections that can amplify as well as rectify.

Watts are units of measurement. The manifestation of power in physical forms such as electromagnetic radiation, acoustic waves, or mechanical phenomena. Voltage and current are in phase in a Direct Current (DC) circuit or an Alternating Current (AC) circuit with pure resistance impedance.

A unit of reactive power measurement. VARS can be thought of as the imaginary part of apparent power or the power flowing into a reactive load, where voltage and current are measured in volts and amperes, respectively.

A variable resistor can be set to a wide range of values.

A unit of apparent power measurement. It is calculated by multiplying the rms voltage by the rms current.

A voltage measurement unit. One volt is equal to the potential difference required to drive one amp of current against one ohm of resistance.

An electromotive force or “pressure” that causes electrons to flow, similar to how water pressure causes water to flow through a pipe. Voltage is measured in volts.

An instrument for measuring the force of an electrical current in volts. This is the potential (voltage) difference between two points in an electrical circuit. Voltmeters with a high internal resistance are connected across (parallel to) the voltage measurement points.

A unit of electrical energy equal to one watt of power consumed for one hour.

A measure of electrical power. One watt is equal to one joule per second, which is the power in an electric circuit with a potential difference of one volt and a current of one ampere.

The wattmeter is a device that measures the electric power or supply rate of electrical energy of any given circuit in watts.

A graphical representation of electrical cycles that shows the amount of amplitude variation over time.