Basic Electrical Terms and Definitions

The Basic Concept of Electricity

Electricity is the flow of electrical current on the conductor. This electric current takes the shape of free electrons that transfer from one atom to subsequent. Thus, the additional free electrons a fabric has, the higher it conducts. Here is the basic electrical terms and definitions.


Types of Electricity

▪ Electricity is mainly in two types:

  1. Static Electricity
  2. Current Electricity

▪ The Current (Locomotive) electricity is two types:

  1. Direct Current (DC)
  2. Alternative Current (AC)


Static Electricity: The electricity which produces in a body by friction is called static electricity. The static electricity remains static in the body. It can’t be preserved.


Current Electricity: The electricity which can flow from one body to another body is called the Current (Locomotive) electricity.


Direct Current (DC): When the flow of electrons does not change the direction or path, the current is called the direct current.


Alternative Current (AC): When the flow of electrons changes the direction or path the current is called the direct current.


Primary Electrical Parameters

† There are three primary electrical parameters


  1. The Voltage

  • It is the amount of electromotive force required to push a current of one ampere through a conductor with a resistance of one ohm.
  • It is denoted as ‘V’. Its unit is Volt or ‘V’.


  1. The Ampere

  • The flow rate of electric current.
  • For instance, once one coulomb (or 6.24 x 1018 electrons) flows past a given purpose on a conductor in one second, it’s outlined as a current of one Ampere or one
  • It is denoted as ‘I’


  1. The Ohm

  • The ohm or ‘Ω’ is a unit of resistance in a conductor.
  • It is denoted as ‘R’


Ohm’s Law Formula

The electric potential across a perfect conductor is proportional to the current through it.

                                    V ∝ I

The constant of proportion,  is called the “resistance”, R.

Ohm’s Law can be expressed as: V = I x R

Where: V = Volts, I = Amps, R = Ohms


Other Important Electrical Terms and Definitions


▪ Frequency

– It defines as the rate of change of direction of current flow in a circuit. It denoted as ‘f’ and its unit is Hertz or Hz


▪ Electric Power

– Electric power is that the rate, per unit time, at that power is transferred by an electrical circuit.

                       P = VI = I2R = V2/R

(Note: For 3  AC, P = VICosθ, Here Cosθ is “Power Factor”)

It is expressed in watt or W.

1 HP = 746 W


▪ Energy

– It defines the electric power consumed for a certain time. It is denoted as E and unit is Watt – Hour or ‘kh’.

1000 watt hour = 1 kwh = 1 unit


▪ Ampacity

– Ampacity is the amount of current conduction can handle before its temperature exceeds accepted limits.


 ▪ Load

– Example – Light, Fan, Motor etc. It mainly rated as watt but also have a rating of V, I, f etc.


▪ Circuit

– An assembly of electrical instrumentation equipped from an equivalent origin and guarded against overcurrent by an equivalent protecting device.


▪ Earth

– The conductive mass of earth, whose electrical potential at any point is conventionally taken as zero.


▪ Cable

– A length of single insulated conductor or 2 or a lot of such conductors every supplied with its insulation which is laid up together.


▪ Switchgear

– Main switches, cutout or fuses etc. Used for controlling or protecting electrical circuits or machines or other current using appliances.


▪ Circuit Breaker

A device designed to open and close a circuit on a predetermined over current. Different type of Circuit Breaker:

  1. MCB (Miniature Circuit Breaker)
  2. MCCB (Molded Case Circuit Breaker)
  3. RCCB (Residual Current Circuit Breaker): used against electric shock.
  4. ELCB (Earth Leakage Circuit Breaker): operates on voltage.
  5. RCBO – Residual Current Breaker with Overload Protection.


Electrical Safety Policy

  • Safety is of paramount importance to the workplace and our home.
  • The building or workplace authorities shall be committed to providing an environment for the safe of electricity and safe work practices.
  • To achieve this, we have a responsibility to eliminate hazards and safely perform all electrical work.


Electrical Safety Goals

  • No persons are killed or injured by electricity; and
  • No property is destroyed or damaged by electricity through firing.


How Person Affected By Electricity?

To flow electricity should have a whole path. Three factors determine the resistance of the path to the flow of electricity. These are:

  1. What it is made of
  2. Its size
  3. Its temperature


Electricity flows through conductors such as-water, metal, and also the body. Insulators are non-conductors such as-rubber. In case of the human body when the skin is dry, it is a poor conductor of electrical current than moist condition. The equipment body is earthed with earthling cable.


The Human body is safe. The equipment body is not earthed. Typically, shock occurs when a person contacts to metallic parts of electric tools and machines when there is a break in the insulation of the wiring.


Electrical safety hazards such as exposure to electric shock and Arc-Flash can be caused by many factors. 10 dangers of electricity,

  1. Carelessness
  2. Broken or worn conductor insulation
  3. Exposed live parts
  4. Loose wire connections
  5. Improperly maintained switches and circuit breakers
  6. Obstructed disconnect panels
  7. Water or liquid near electrical equipment
  8. High voltage cables
  9. Static electricity
  10. Damaged tools and equipment


Power Factor

In an AC circuit, a power factor is defined as the phase difference or phase angle between current and voltage. The low power factor always affects the whole power system in different ways. Such as;

  • Large KVA rating of the equipment.
  • Greater conductor size.
  • Large copper losses
  • Poor voltage regulation

▫ The Reduced handling capacity of the system.

  • It is noted as Cosθ. Or ‘pf’
  • It is value always unity or less than unity.


Some Important Electrical Equipment



A system of electrical conductors during a generating or receiving station on that power is focused for distribution.


Earth Electrode

A typical earthing electrode consisting of a conductive rod driven into the ground, It is used to protect a person from an electric shock, by providing a path for a fault current to flow to earth.


ECC (Earth Continuity Conductor)

It’s a stranded cable or the other conductor that is connected along with all metal components of associate electrical installation. E.g. switch fuses, fuse distribution board, steel passage, a metal framework on that electrical equipment is mounted.


Abbreviated Terms and Important Definition

SB: Switch Board

AC: Alternating Current

DB: Distribution Board

GI: Galvanized Iron

HT: High Tension (High Voltage)

LT: Low Tension (Low Voltage)

IR: Insulation Resistance

PPE: Personal Protective Equipment

PFI: Power Factor Improvement

PVC: Polyvinyl Chloride

PIB: Phase Isolated Bus

REB: Rural Electrification Board

SDB: Sub Distribution Board

SLD: Single Line Diagram

SWG: Standard Wire Gauge

UPS: Uninterruptible Power Supply

ECC: Earth Continuity Conductor

MDB: Main Distribution Board

MCB: Miniature Circuit Breaker

NFPA: National Fire Protection Association

BNBC: Bangladesh National Building Code

LOTO: Lockout/Tag-out

MCCB: Moulded Case Circuit Breaker


Leave a Comment