Electrical Theory

 

Electrical Theory

Every aspiring electrician needs to have a solid foundation in electrical theory from the beginning.

Understanding the power you're working with in principle can assist in keeping you, and others secure because electricity has no sound, no smell, and cannot be seen. To ensure appropriate installation and to carry out duties like repairing electrical systems and equipment, the electrical theory is crucial for understanding the function and functioning of electrical equipment.

 Atomic Structure and electrical circuit  

Arrangement of the Atom

The smallest component of matter is the atom. Three components make up an atom.

The nucleus, located in the atom's heart, is made up of positively charged protons.

The remainder of the nucleus comprises neutrons, which are uncharged particles. Negatively charged electrons also circle the nucleus.

 

 

 

 

 

Valence shell

The core of an atom is surrounded by a set number of shells, each of which has a specific number of electrons.

2 electrons in the first shell

8 electrons in the second shell

18 electrons in the third shell

32 electrons in the fourth Shell

Its maximum density is 8 valence electrons, known as the valence shell. This shell determines a substance's conductor, insulator, or semiconductor status.

 Electric Circuit

An electrical circuit, often called an electrical system, is created by connecting several active and passive elements in a specific order to create a closed channel. Electric current should be capable of going from the source to a conductive medium to finally return to the source's other terminal.

The essential components of a perfect electric circuit are:

• Electric storage is the main electrical source that supply electricity to the circuit.
• Switches, breakers, and additional devices resembling potentiometers are the major controlling devices used to regulate electricity.
• Electric fuses and switchgear systems are the most common protection devices that shield the circuit from unusual conditions.
• Conducting paths are used in circuits to move electric current from 1 junction to another.

 

 

                                         

 

Terms

1. An alternating current (AC) is an electric current in a circuit that periodically reverses direction and magnitude.

2. A closed circuit is a closed channel or circuit that an electric current can follow.

3.  A conductor is a substance or thing that permits the flow of current.

4. The quantity of electrons moving past a specific circuit point in a given amount of time is known as current and is measured in amperes or amps.

5. Electricity that only flows in one direction is known as direct current.

6. The insulator is a material or object that resists electricity's easy conduction.

7. A multi meter is a test device for electrical systems measuring various quantities, typically voltage, current, and resistance.

8. An open circuit is a path that blocks the movement of current.

9."Resistance" refers to a body's or substance's opposition to a current traveling through it. It causes electrical energy to transform into another type of energy.

10. Electromotive force, often known as potential difference, is measured in voltage or volts.

11. The watt is the SI unit for measuring power, it is equal to one joule per second and represents the power in an electric circuit with a voltage and current of one volt and one ampere, respectively

12. Series circuit: A grouping of electrical components or circuits that allow current to flow each after the other. The current flow has one route. A circuit is called a series circuit when all its components are linked, tail to head, creating only one path for electricity to flow.

13. A short circuit is called a channel with low resistance that allows an excessive current to pass through.

14. In a parallel circuit, each component has the same voltage drop, but the currents that pass through them may vary. The sum of the ‘I’ passing through each constituent is the total current. All elements in a circuit with parallel connections have the same voltage.

 Electrical Current Flow Theories         

This (incorrect) convention continues to exist now and is commonly called conventional current flow. However, before the real nature of electrical energy became known, scientists assumed the flow of current had been a consequence of the flow of positively charged particles and that, therefore, current flowed from the negatively charged end of the battery's charge to the positive terminal.

 What is an electric charge? A fundamental physical characteristic is a charge. We can only explain how charged particles act; we cannot describe what it is.

·         A charged particle possesses an electrical charge.

·         Protons and electrons both have charges.

·         Protons have a + charge 

·          Electrons have a - charge.

·         Like charges repel and opposing charges attract.      

 The amount of charge, the charge on a single electron is too little. To measure electrical charge, coulombs (C) are used. The entire charge delivered every 6.25 x 10¹⁸ electron is equivalent to one coulomb.    

 Ohm's law

Current (I)

An electrical current is a gauge for the speed at which charge moves through it. I.e. Current (I) is a unit of measurement for the amount of charge (Q) that travels through a location in a circuit in one second (t).

I = Q/t.

 The current, I, is expressed in amps (A).

The total charge, or Q, is expressed in Coulombs (C).

 The amount of time in seconds (s) it takes for a charge to move through a certain point in an electrical circuit is called t.

 

                               

Voltage & Resistance

An electrical power source, like a battery, creates a voltage. Current flows in a circuit of electricity as a result of voltage. The current is going to be greater, the higher the voltage. The term "resistance" is used more frequently in DC theory. The unit of resistance is the Ohm ().

According to Ohm's law, the voltage across a resistor determines how much current flows through it. Resistance is the proportion of the voltage across an object to the current passing through it.

R = V/I, which means

R stands for resistance in ohms.

V stands for voltage in volts.

I equal current in amps (A).

Resistance limits the current that can pass through a part and turns the electrical energy into heat. If at least two of the three parameters are known, the law of ohms can be used to calculate the circuit's current, voltage, or resistance.

Example.

If we know the voltage being applied and the overall resistance of the circuit, we can use Ohm's Law to determine the current that will travel within the circuit.

Solution

A cut is wired to a 12V power source. How much current will move using it if its resistance is 5 Ohms?

R = V/I, hence I = V/R, which equals 18/6 and 3A.

Energy

 The ability to perform tasks is called energy. Accordingly, anything capable of changing or moving in any form possesses energy.

Energy conservation.

 Energy cannot be generated and destroyed, according to this. Energy can, however, be changed from one kind to another.

The potential energy in electricity

Electrons are moved from the positively charged end of a battery to the negative terminal by an electromotive force, which raises their electrical potential (E), in an electrical power source like a battery. As the electrons are moved between the battery terminals, the increase in potential electricity is a gauge of the energy given per Coulomb.

As the charge is transported between the two ends of the power source, electrical potential serves as a gauge for the energy delivered per Coulomb.

 

Voltage

Voltage is a unit used to describe electrical potential.

When V = W/Q, where:   

The voltage or electrical potential is expressed in volts (V).

W represents the charge's electrical potential energy, expressed in Joules (J).

The amount of charge, or Q, is expressed in Coulombs (C).

An electrical potential difference between two places in a circuit is known as a potential difference. For instance, there is a potential difference between a battery's terminals. The negative terminal's electrons have greater potential than the one from the positive terminal's electrons.

The electrically charged potential of the charged particles is raised through an emf  e.g., the emf increases the possibility of the charged particles as it moves between the battery's terminals, which causes the voltage across the battery to rise. A larger potential exists in the electrons, leaving the opposite termination compared to those entering the positive terminal.

A component's resistance is determined by the electrical characteristic of the material it is built of. Resistivity is the name of this quality.

 

 Insulators, Semi-Conductors, and Conductors

Conductors are substances that allow current to circulate comparatively easily while possessing a high number of densely packed electrons that are free.

Insulators are substances with extremely low number density, high resistance, and low number density.

Semiconductor materials have resistance and number density values that fall between the values for conductor and insulator.

The free electrons move toward the positive potential when an electrical field is created within a conductive material. Due to thermal power, they continue to move randomly but are now moving away from the previously mentioned "fixed" position.  

Kirchhoff's Laws

Kirchhoff's 1st Law

According to Kirchhoff's Current Law, the total amount of current flow in and out of the junction in a circuit of electricity must be equal.

(In an electrical circuit, a junction connects multiple conductors.)

Kirchhoff's current Law illustrates the rule of conservation of charges used in an electrical circuit at a junction.

According to the conservation of charge, the charge cannot be produced or dissipated. If the current coming into a junction weren't equivalent to the flow of current out, this would suggest that charge was either transferred or lost at the connection, as current is exclusively the speed at which electrical charge flows! It would break the principle of charge conservation.

(A node is another name for a junction within an electrical circuit.)

 

                                                    

                                                            Kirchhoff's 1st Law

 

 

Kirchhoff's second law

According to Kirchhoff's Voltage Law, the e.m.f given to each loop in a circuit equals the total voltage drops across that loop. According to Kirchhoff's Voltage Law, all e.m.f.s applied to a circuit's loops equals all voltage drops across the loop's perimeter.

The current can only move around one loop at a time. Two voltage decreases (one across each resistor, V1 and V2)) happen in this loop.

E is equal to V1 plus V2.

 

                                                         

                                                Kirchhoff's second law