Practical Electronics/Basic Theory

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Electrostatic Charge[edit]

Electrostatic refers to the process of matter becomes Electric Charge

Electric Charge[edit]

Normally all matter are neutral or have net Charge equal to zero . When an object lose or gain electron . Object becomes Positive Charge or Negative Charge .

Matter + e --> -
Matter - e --> +

All Charges pocess a Quantity of Electric Charge called Electric Charge denoted as Q measured in Couloum (C) an Electric Field made of Electric Field Lines radiate outward or inward . For Negatively Charge, the Electric Field Lines radiates inward . For Positively Charge, the Electric Field Lines radiates outward. Electric Field is denoted as E measured in N/C .

Negative Charge , -Q . ---> Negative Charge <--- .
Positive Charge , +Q . <--- Positive Charge --->

Charges interact with each other according to Coulomb's Law

Like Charges repulse . Unlike Charges attract , 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 Force[edit]

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 Force[edit]

electroDynamic force produced by potential

Charge & Electric Force[edit]

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 Force[edit]

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 Force[edit]

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 Electricity[edit]

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 Electricity[edit]

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 pressure 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 . Voltage is denoted as V measured in Volt v .

1v = 1J / 1C


Current is defined as number of electric charges flow through an area of conductor in a period of Time . Current is calculated by the ratio of Electric Charge on Time . Current is denoted as I measured in Ampere A

1A = 1C / 1s


Power is defined as Energy of a Work over Time. Power is calculated by the product of Voltage and Current . Power is denoted as P measured in watt or Volt Amp VA

, vA or J/sec or watt
1 watt = 1v x 1A


Resistance is defined as the ratio of Voltage over Current . Resistance is denoted as R measured in Ohm

1 = 1V / 1A

Resistance & Temperature[edit]

It's been observed that Resistance of a conductor changes with change in Temperature

R = Ro + nT For Conductor
R = Ro enT For Semi Conductor

Resistance & Electric Power Loss[edit]

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