Practical Electronics/Basic Theory

Electrostatic ChargeEdit

Electrostatic referring to the stationary electric charge that are built up on an insulating material.

Electric ChargeEdit

Normally all matter are neutral or have net Charge equal to zero . When an object loses or gains an electron , that object will either becomes positively charged or negatively charged .


All Charges possess a quantity of Electric Charge called Electric Charge denoted as Q measured in Coulomb (C). An Electric Field made of Electric Field Lines radiate outward or inward . For Negatively Charge, the Electric Field Lines radiates inward ,otherwise for Positively Charge, the Electric Field Lines radiates outward. Electric Field is denoted as E measured in N/C .

Negative Charge , 
Positive Charge , 

Charges interact with each other according to Coulomb's Law.

Same Charges repulse . Different Charges attract ,i.e Negative Charge attract Positive Charge


The interaction of charges cause a force of repulsion or attraction between charges. this force of repulsion or attraction cause electricity

ElectroStatic ForceEdit

ElectroStatic Force or Coulomb Force is the force of attraction between two unlike Charges . For 2 static point charges of different polarities lying in a straight line on a plane . The force of attraction of the two point charge can be calculated by Coulomb's Law

F , Electric Force of Attraction
k , Constant of Attraction
r , Distance of separation

ElectroDynamic ForceEdit

electroDynamic force produced by potential

Charge & Electric ForceEdit

If there is a Electric Force that sets stationary charge in straight motion to cause a flow of charge called Current then the Electric Field can be calculated by Ampere's Law

F = E Q

Charge & Magnetic ForceEdit

If there is a Magnetic Force that can change the direction of the moving charge perpendicular to the initial direction of moving charge, such that Positive charge will moved up perpendicular to the initial direction and Negative Charge will move down perpendicular to the initial direction, then Magnetic Field can be calculated by Lorentz's Law

F = B v Q

ElectroMagnetic ForceEdit

The total force acting on the moving charge is the sum of the Electric Force calculated by Ampere's Law plus the Magnetic Force calculated by Lorentz's Law. The sum of Ampere's Force and Lorentz's force is called ElectroMagnetic Force

F = E Q + B v Q = Q ( E + v B )

Matter and ElectricityEdit

Matter that interact with Electricity is divided into three groups Conductor,Non Conductor,Semi Conductor depends on the ease of how current flow in the matter

All matter that allows current to flow with ease are called Conductor. For example all Metals like Zinc (Zn), Copper (Cu) are used to make Conductor
All matter that does not allow current to flow in it are called Non Conductor . For example Rubber
All matter that allows current to flow somewhere between conductor and non conductor are called Semi Conductor . For example Silicon (Si), Gemanium (Ge)

Conductor and ElectricityEdit

When connect conductor with source of Electricity in a closed loop circuit . The Force of Electricity will exert a pressure to make conductor's charges to move in a straight line . The pressure of the Electricity Force is called Voltage denoted as V measured in Volt (v) . The straight line movemoment of charges in the conductor is called Current denoted as I measured in Amp (A)


Voltage is defined as the potential differences of the electricity force to make charges in the conductor to move in straight line and calculated by the ratio of work done on an electric charge .The larger the potential difference, the larger the flow of charge. It appears across a pair of points in a circuit, such as the terminals of a battery.

Voltage is denoted as V measured in Volt (V) and the formula is shown below:

  , where  


Current is defined as flow rate of electric charges flow through an area of conductor in a period of time and is calculated by the ratios of electric charges flow rate over time . Current is denoted as I measured in Ampere (A) and the formula is shown below:

  , where as  


Power is defined as work done over time and is calculated by the product of voltage and current . Power is denoted as P measured in Watt or Volt Amp (VA) and the formula is shown below:



Resistance is defined as voltage across the conductor divided by the current flowing and is calculated as voltage over current. It is also one of properties of a conductor by virtue of when the passage of current is opposed, it will cause electric energy to be transformed into heat
Resistance is denoted as Ω measured in Ohm Ω with formula shown below:

Resistance & TemperatureEdit

It's been observed that Resistance of a conductor changes with change in temperature
  where :
R1 = Conductors resistance at temperature T1
R2 = Conductors resistance at temperature T2
α1 = Temperature coefficient of the material
T1 = Reference temperature at which α1 is specified
T2 = Conductor present temperature

Resistance & Electric Power LossEdit

Also, When conductor of resistance R conducts current . Conductor releases Heat Energy into the surrounding result in loss of Electric Power Energy directly proportional to the resistance of the conductor


Without Energy loss the Power supplied is Pi


With energy loss PR known as Power Loss or Dissipated Power


The real Power supplied would be


The efficiecy of Power transmission can be calculated as the percentage of Real Power over the Supplied Power



Conductance is defined as the ratio of Current over Voltage . Conductance is denoted as Y measured in Siemen 1 / Ω

1S = 1A / 1V