Industrial Electricity: Basic Electrical Circuits [1]

A. Electric Charge, Current, voltage and Power

Before we study about Electrically deep inside just take a look the philosophy about it here:

A.1 Electric Charge (q)

                 Atom theory that said by Mr.Dalton describe if Atom is a smallest thing that can not be divided anymore. In fact, atom consist of ion that have their own charges. Charges that atoms have are:

– Positive charge called Proton

– Neutral charge called Neutron

– Negative Charge called Electron

Picture 1. Atom that configure by three of charges

 picture 1 showed that proton and neutron will form a nucleus or the central of atom. Electron will move around the central like earth surround of sun. Electric charge have a unit that called as “coulomb” (maybe like the name of the finder). Electron who have moved surround the central of atom represents this atom value.

So, we can take a conclusion here if electric charge that can make any free movement is Electron.

A.2 Electric Current (I)

          We will try to understand the relation about electric charge and current itself. Before we talked more deeply, first time we can imagine electric current like river flow. River flow is formed by water that move in the river on a time, actually electric current also represents a movement of electron in a wire on a second.


               Pic 2. River Flow                                                                                                     Picture 3. electric current

             Because of electric current is the movement of electron so we can measure the value of current itself. Electric current have unit called “Ampere”. 1 ampere can be defined as movement of an electron that have value e(-) = -1.602 x 10^(-19) coulomb in a second. So we can make an equation for electric current with:

I = q / t


I = current in Ampere

q = value of charge in coulomb

t = time in second

                     When we see about river flow beside have a value they also have a direction. Electric current not only have  a scalar value but also a vector value. Take a look in a picture 3. There are a direction for electron movement (from – to +) that called by electron flow, but electric current moved otherwise (from + to -). So we can make a difference between electron flow and electric current.

The direction that electric current have is not called as west, north, east,etc. The direction show as a positive and negative direction. In an electrical there are two kinds of current they are:

Picture 5 symbols of AC and DC

*Alternating current (AC)

–> mean an electric current that have a changeable direction depend on the changing of time.

*Direct current (DC)

 –> mean an electric current that have a no changeable direction on the changing of time.


 A.3 Electric Voltage or Differential of potential (V)

 Before we talk about Voltage we must understand about it:

 Picture6. Flow philosophy

We can take any conclusion from picture6 that water can be flow of water when they placed on differential higher place. As water do, electrical charge also move when there are two or more poles have difference potential.

We can define about voltage if they are an energy that needed to make 1C electric charge. Here the equation:

V = J/C


V = mean voltage, with the volt unit

J = energy, with Joule unit

C = electric charge, with Coulomb unit


  A.4 Electric Power (P)

 Electric power is defined by an effort that needed to make 1 Joule of energy flow to send 1 Coulomb of electric charge in  a device on a second. Electric power have unit Watt, a can be equated by:

P = V.I


P = mean electric power, unit is watt

V = voltage, unit is volt

I = electric current, unit ampere


   A.5 Source of Voltage

Source of power is a device that made to transfer a power. Because there are two kinds of current so we also can divided a source of voltage into two, they are:

>> AC source of voltage : generator, PLN, etc

>> DC source of voltage : accumulator and battery

 This is the end of part one in a basic of Electrical industrial theory ….^_^. Keep on studying and keep on moving forward.

Record on: Jakarta 19th September of 2011

Source : Rangkaian Listrik, Jilid 1, Edisi Keenam, Hayt Kemmerly Durbin

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