Electrical Electrical wiring wiring

Let there be Let there be light….light….

ElectricityElectricity• Electricity is a form of energy that can produce light, heat, Electricity is a form of energy that can produce light, heat,

magnetism, chemical changes. It is the second energy source, magnetism, chemical changes. It is the second energy source, which means that we get it from the conversion of other energy which means that we get it from the conversion of other energy source. source.

• One might define electricity as the separation of positive and One might define electricity as the separation of positive and negative electric charge.negative electric charge.

• In a simple way electricity is movemet of electrons of a In a simple way electricity is movemet of electrons of a conductor. conductor.

• When the charges are separated and stationary we call this When the charges are separated and stationary we call this static electricity. The charging of a capacitor is an example. static electricity. The charging of a capacitor is an example.

• The separation of charge between clouds and the earth before a The separation of charge between clouds and the earth before a lightening discharge is a static electricity.lightening discharge is a static electricity.

• When the charges are in motion we have variable electricity.When the charges are in motion we have variable electricity. • Electronics refers to the flow of charge (moving electrons) Electronics refers to the flow of charge (moving electrons)

through nonmetal conductors (mainly semiconductors), whereas through nonmetal conductors (mainly semiconductors), whereas electrical refers to the flow of charge through metal conductors. electrical refers to the flow of charge through metal conductors. For example, flow of charge through silicon, which is not a metal, For example, flow of charge through silicon, which is not a metal, would come under electronics; whereas flow of charge through would come under electronics; whereas flow of charge through copper, which is a metal, would come under electrical.copper, which is a metal, would come under electrical.

How is Electricity How is Electricity Produced?Produced?

• Friction:Friction: “static electricity” from rubbing or “static electricity” from rubbing or walking across a carpet.walking across a carpet.

• Pressure:Pressure: piezo electricity from squeezing piezo electricity from squeezing crystals together (quartz watch)crystals together (quartz watch)

• Heat:Heat: voltage produced at junction of voltage produced at junction of dissimilar metals (thermocouple)dissimilar metals (thermocouple)

• Light:Light: voltage produced from light striking voltage produced from light striking photocell (solar power)photocell (solar power)

• Chemical:Chemical: voltage produced from chemical voltage produced from chemical reaction (wet or dry cell battery)reaction (wet or dry cell battery)

• Magnetism:Magnetism: voltage produced using voltage produced using electromotive inductionelectromotive induction (AC or DC (AC or DC generator). generator).

Electricity BasicsElectricity starts with electrons. Every atom contains one or more electrons.

Electrons have a negative charge.

The atomThe atom

Nucleus : Protons (+) and neutrons

Electrons (-) rotating on orbits or energy bands which

are called shells

Valence electrons: Electrons that are in

the orbits farther from the nucleus

Basic ElectricityBasic Electricity• ProtonsProtons

• Positively charged particles located at the Positively charged particles located at the center, or nucleus, of each atomcenter, or nucleus, of each atom

• ElectronsElectrons• Small very light particles with a negative Small very light particles with a negative

electrical chargeelectrical charge• These electrons move in orbit around the These electrons move in orbit around the

nucleus of an atom.nucleus of an atom.• NeutronsNeutrons

• Do not have an electrical chargeDo not have an electrical charge• These particles add weight to the atomThese particles add weight to the atom• Located at the nucleus of an atomLocated at the nucleus of an atom

BasicBasic ElectricityElectricity

• Electron MovementElectron Movement• The outer ring of an atom is called the The outer ring of an atom is called the

valance ringvalance ring• The number of electrons on the valance The number of electrons on the valance

ring determine the electrical characteristics ring determine the electrical characteristics • Current flow may be defined as the mass Current flow may be defined as the mass

movement of valence electrons from atom movement of valence electrons from atom to atom through a conductorto atom through a conductor

Terms used in Terms used in ElectricityElectricity

• Electricity is a form of energy that can produce Electricity is a form of energy that can produce light, heat, magnetism, chemical changeslight, heat, magnetism, chemical changes

• Resistance: tendency of a material to prevent Resistance: tendency of a material to prevent electrical flowelectrical flow

• Conductor: if electricity flows easilyConductor: if electricity flows easily• Insulator: material that provides great resistanceInsulator: material that provides great resistance• Amperes: measure of the rate of flow of Amperes: measure of the rate of flow of

electricity in a conductorelectricity in a conductor• Volts: measure of electrical pressureVolts: measure of electrical pressure• Watts: measure of the amount of energy or work Watts: measure of the amount of energy or work

that can be donethat can be done• Ohms: measure of electrical resistance to flowOhms: measure of electrical resistance to flow

Most metals have electrons that can detach from their atoms and move around. These are called free electrons. Gold, silver, copper, aluminum, iron, etc., all have free electrons. An element with 1, 2, or 3 valance electrons is a good conductor of electricity

Conductors

Elements with less than 4 Electrons in their

outer rings make good conductors1 32

Because the Electrons are easily dislodged from their orbit and pushed to the atom

next to them. (Electron flow)

Basic Electricity Cont.Basic Electricity Cont.• SemiconductorsSemiconductors

• An element with 4 valance electronsAn element with 4 valance electrons• Used to manufacture diodes and transistorsUsed to manufacture diodes and transistors• Silicone is one of the most common Silicone is one of the most common semiconductorssemiconductors

In many materials, the electrons are tightly bound to the atoms. Wood, glass, plastic, ceramic, air, cotton ... These are all examples of materials in which electrons stick with their atoms. Due to the electrical attraction of the electrons and protons it is very difficult to get the electrons to move. Since the electrons don't move, these materials cannot conduct electricity. These materials are electrical insulators. These material have 5 or more electrons on the valance ring .

Insulators

Elements with More than 4 Electrons in their outer rings make good insulators

5 7

Because the Electrons remain in the outer rings when electromotive force

( Voltage) is present.

Electric chargeElectric charge• The proton and the electron exhibit a force of The proton and the electron exhibit a force of

attraction due to their electrical charge. The attraction due to their electrical charge. The proton is said to be charged positive(+) and proton is said to be charged positive(+) and the electron negative(-). They have the same the electron negative(-). They have the same magnitude but opposite charge. magnitude but opposite charge.

• The electron electric charge is 1.6 x 10The electron electric charge is 1.6 x 10-19-19 Coulombs.Coulombs. Current always flow from :Current always flow from :

• Positive terminal to the negative terminal Positive terminal to the negative terminal as per the conventional theoryas per the conventional theory

• Negative terminal to the positive terminal Negative terminal to the positive terminal as per electronic theory.as per electronic theory.

CoulombCoulomb

•A coulomb is a count of the number of electrons passing a given point on a conductor in one second.

•The number of electrons in a coulomb is 6.24 x 1018 or 6,240,000,000,000,000,000

•One coulomb per second equals one amp.

•The charge is expressed as Q or q. If the charge is constant we use Q. If the charge is in motion we use q(t) or q.

•According to fundamental laws, charge cannot be either created or destroyed, only transferred from one point to another.

Ampare1 amp physically means that 6.24x10 electrons move through a wire every second. 1 ampere = 1coulomb/second

18

t

Qi

We normally refer to current as being either direct (dc) or alternating (ac).

i(t) i(t)

t t

d c cu rren ta c c urre nt

0 0.5 1 1.5 2 2.5 3 3.5-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

a c c u rre n t

18

AmmeterAmmeter

• Instrument that measures the rate of current flow in ampares.

•There are two types of ammeter:

• the DC ammeter

• the AC ammeter.

• Caution: An in-line ammeter should Caution: An in-line ammeter should always be connected in series always be connected in series with the the circuit. If accidentally connected in circuit. If accidentally connected in parallel, it will burn up.parallel, it will burn up.

VoltVolt• Volt is theVolt is the pressure used to force pressure used to force the electrons from one atom to the electrons from one atom to another.another.

• One volt is the force required to push One volt is the force required to push one amp through one ohm of one amp through one ohm of resistance.resistance.

• The volt is unit of electrical pressure, The volt is unit of electrical pressure, similar to pressure used to make gases similar to pressure used to make gases and liquids flow through pipes.and liquids flow through pipes.

•

Voltage sourcesVoltage sources

Battery Solar cell

Generator

Power supply

• A solar cell is a device that converts the A solar cell is a device that converts the energy of sunlight directly into electricity by energy of sunlight directly into electricity by the photovoltaic effect. the photovoltaic effect.

Simple explanation of Simple explanation of solar cell.solar cell.

• Photons in sunlight hit the solar panel and are Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as absorbed by semiconducting materials, such as silicon.silicon.

• Electrons (negatively charged) are knocked loose Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through from their atoms, allowing them to flow through the material to produce electricity. Due to the the material to produce electricity. Due to the special composition of solar cells, the electrons special composition of solar cells, the electrons are only allowed to move in a single direction. are only allowed to move in a single direction. Complementary positive charges, called holes, Complementary positive charges, called holes, are also created and flow in the opposite are also created and flow in the opposite direction to the electrons.direction to the electrons.

• An array of solar cells converts solar energy into An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.a usable amount of direct current (DC) electricity.