Circuits 1 – Module Circuits 1 – Module 2A2A

ELEL31EELEL31E

Prepared by:Prepared by:

Engr. Ronaldo AmosEngr. Ronaldo Amos

Circuits 1 – Module 2ACircuits 1 – Module 2A

►Definition of ElectricityDefinition of Electricity► SI System of MeasurementSI System of Measurement► Electric chargeElectric charge► Structure of matterStructure of matter► Electrical classification of materialsElectrical classification of materials► Electric field and electric forceElectric field and electric force► Electric potentialElectric potential► Electric current, direction of flowElectric current, direction of flow►Material resistance Material resistance

Fundamentals of ElectricityFundamentals of ElectricityElectricity Electricity ► Is an electric charge, or an electrical energy or Is an electric charge, or an electrical energy or

electromagnetic energyelectromagnetic energy Static electricityStatic electricity Moving electric currentMoving electric current

► Phenomenon associated with the presence and Phenomenon associated with the presence and motion of electrons and other charged particlesmotion of electrons and other charged particles

► The physical phenomena arising from the behavior The physical phenomena arising from the behavior of electrons and protons that is caused by the of electrons and protons that is caused by the attraction of particles with opposite charges and attraction of particles with opposite charges and the repulsion of particles with the same charge. the repulsion of particles with the same charge.

► The flow of electrons and protons in a closed circuit The flow of electrons and protons in a closed circuit due to electric charge. due to electric charge.

► When a potential difference between two charges When a potential difference between two charges forces a third charge to move, the charge in motion forces a third charge to move, the charge in motion is called and electric current.is called and electric current.

► The flow of electric current in a closed circuitThe flow of electric current in a closed circuit

► SI system of measurementSI system of measurement SI stands for International System of UnitsSI stands for International System of Units At present, two major systems—the English (US

Customary) and the metric—are in everyday use.►Examples of metric: meter, kg, ampere, joule, hertz, ohm►Examples of English: inch, pound, ft, horsepower, ft-lb

The SI system combines the MKS metric units and the electrical units into one unified system

Though the use of SI system is very wide, there are instances where expressing it in English system is more practical. For example, the HP as a unit of power is preferred over W when it comes to very large quantities. Thus, it is necessary to know the conversion of these units from SI to English and vise-versa.

►Unit Conversion Example: convert 12 cm to inches 12cm x 1in/2.54cm = 4.72 in

Unit PrefixesUnit Prefixes

► Kilo = K = 10Kilo = K = 1033

► Mega = M = 10Mega = M = 1066

► Giga = G = 10Giga = G = 1099

► Tera = T = 10Tera = T = 101212

► Milli = m = 10Milli = m = 10-3-3

► Micro = µ = 10Micro = µ = 10-6-6

► Nano = n = 10Nano = n = 10-9-9

► Pico = p = 10Pico = p = 10-12-12

Usually resistances are expressed in Usually resistances are expressed in , K , K , M , M , , and G and G ..

Amperes are usually expressed in A, mA, and µA. Amperes are usually expressed in A, mA, and µA. Voltages in electronics are usually expressed in V, Voltages in electronics are usually expressed in V,

mV, and mV, and µV. In electrical, voltages may go up to µV. In electrical, voltages may go up to several KV, several KV, and MV.and MV.

Conversion of UnitConversion of Unit

Sample Problem:Sample Problem:

► Electric charge (Q)Electric charge (Q) Is a fundamental property of matter and is Is a fundamental property of matter and is

influenced by elementary particles such as influenced by elementary particles such as electrons and protonselectrons and protons

A body is said to be charged, if it has an excess A body is said to be charged, if it has an excess or deficit of electrons from its normal values due or deficit of electrons from its normal values due to sharing.to sharing.

The quantity of electron flow or chargeThe quantity of electron flow or charge►2 kinds of charges according to Benjamin Franklin (US 2 kinds of charges according to Benjamin Franklin (US

scientist: 1706 – 1790)scientist: 1706 – 1790) Positive charge (carried by protons)Positive charge (carried by protons) Negative change (carried by electrons)Negative change (carried by electrons)

Unit: Coulomb Symbol: CUnit: Coulomb Symbol: C►Named after the French physicist, Charles Augustin de Named after the French physicist, Charles Augustin de

Coulomb (1736 – 1806)Coulomb (1736 – 1806)►1 coulomb = 6.242 x 101 coulomb = 6.242 x 1018 18 electronselectrons►Electron charge = 1/6.242 x 10Electron charge = 1/6.242 x 1018 18 = 1.602 x 10-= 1.602 x 10-19 19 CC

Like poles repel, unlike poles attract. Like Like poles repel, unlike poles attract. Like charges repel, unlike charges attract.charges repel, unlike charges attract.

► Structure of MatterStructure of Matter The elementary particles are basic form of matter, The elementary particles are basic form of matter, and as they combine they form another matter, and as they combine they form another matter, the atom; and as atoms combine forms yet another different matterthe atom; and as atoms combine forms yet another different matter MatterMatter – is anything in the universe that has mass, occupies space, – is anything in the universe that has mass, occupies space,

and is convertible to energy.and is convertible to energy. Compound Compound – a combination of two or more different atoms or – a combination of two or more different atoms or

elements.elements. Element Element – substance consisting of atoms of only one kind. This is – substance consisting of atoms of only one kind. This is

considered as the elementary (irreducible) chemical identity of considered as the elementary (irreducible) chemical identity of materials which means that it cannot be decomposed any further by materials which means that it cannot be decomposed any further by chemical action.chemical action.

Molecule Molecule – the smallest particle that a compound can be reduced – the smallest particle that a compound can be reduced before it breaks down into its elements. It’s the smallest part of a before it breaks down into its elements. It’s the smallest part of a compound or material that retains all the properties of the compound or material that retains all the properties of the compound.compound.

AtomAtom – smallest part of that an element can be reduced to and still – smallest part of that an element can be reduced to and still keeping the properties of the element.keeping the properties of the element.

Atomic numberAtomic number – represents the number of protons in the nucleus – represents the number of protons in the nucleus of an atom, which in a neutral atom equals the number of electrons of an atom, which in a neutral atom equals the number of electrons outside the nucleus.outside the nucleus.

Atomic massAtomic mass – mass of the atom, which represents the sum of – mass of the atom, which represents the sum of protons and neutrons. Electrons has a relatively very small mass protons and neutrons. Electrons has a relatively very small mass and therefore neglected.and therefore neglected.

Valence electronsValence electrons – electrons found in the outermost shell or orbit – electrons found in the outermost shell or orbit of an atomof an atom

Electron charge = -1.602 x 10-19 CProton charge = +1.602 x 10-19 CNeutron = 0 C

• Electric current – the directional motion of electrons• Electrostatics – deals with stationary charged particles• Magnetism – effects of moving electrons• Electromagnetism – magnetism due to electric current.

Joseph John Thomson (1856 – 1940)A British physicist who discovered the electron in 1897, which he initially called corpuscles, meaning a living cell.

Bohr Atomic Model

► Bohr Atomic ModelBohr Atomic Model Niels Henrik David Bohr (1885 – 1962)Niels Henrik David Bohr (1885 – 1962)

►Danish physicist who in 1913 developed a new model of Danish physicist who in 1913 developed a new model of atomic structure call the Bohr Atomic Model.atomic structure call the Bohr Atomic Model.

In this model, electrons travel in defined circular In this model, electrons travel in defined circular orbits around the nucleus. The orbits are labeled orbits around the nucleus. The orbits are labeled by an integer, the quantum number n.by an integer, the quantum number n.

Electrons can jump from one orbit to another by Electrons can jump from one orbit to another by emitting or absorbing energy.emitting or absorbing energy.

The maximum number of electrons (Ne) that can The maximum number of electrons (Ne) that can occupy a given shell or the noccupy a given shell or the nthth shell can be shell can be approximated by:approximated by:►Ne = 2nNe = 2n22 where n is the nwhere n is the nthth shell shell►Example: Cu 29 electronsExample: Cu 29 electrons

11stst shell, n=1; Ne = 2 electrons shell, n=1; Ne = 2 electrons 22ndnd shell, n=2 ; Ne = 8 electrons shell, n=2 ; Ne = 8 electrons 33rdrd shell, n= 3; Ne = 18 electrons shell, n= 3; Ne = 18 electrons 44thth shell, Ne = 1 valence electron = 29 – 28 shell, Ne = 1 valence electron = 29 – 28 Note: the farther the electron from the nucleus, the higher Note: the farther the electron from the nucleus, the higher

is its energy levelis its energy level

►Mass of Mass of Electron = 9.109 x 10Electron = 9.109 x 10-13 -13 kgkg Proton = 1.673 x 10Proton = 1.673 x 10-27 -27 kgkg Neutron = 1.673 x 10Neutron = 1.673 x 10-27-27 kg kg

► Charge to mass ratio (C/kg)Charge to mass ratio (C/kg) Electron = 1.76 x 10Electron = 1.76 x 101111

Proton = 3.58 x 10Proton = 3.58 x 1077

► Valence shell – is the outer most shell or the Valence shell – is the outer most shell or the last shell.last shell.

► Free electrons – are originally valence Free electrons – are originally valence electrons. As they gain enough energy they electrons. As they gain enough energy they escape from the valence shell and become escape from the valence shell and become freefree Free electrons do not remain permanently Free electrons do not remain permanently

associated with the atoms of a solid, they move associated with the atoms of a solid, they move from one atom to another and during conduction from one atom to another and during conduction of electricity, it is these free electrons that will be of electricity, it is these free electrons that will be in motion.in motion.

Coulomb’s LawCoulomb’s Law► The force between charges was studied by the French

scientist Charles Coulomb (1736–1806).► Coulomb determined experimentally that the force between

two charges Q1 and Q2 (Figure 2–5) is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

• where Q1 and Q2 are the charges in coulombs, • r is the center-to-center spacing between them in

meters, and • k = 9 x 109.

ElemenElementt

#of #of ee

#of #of pp

#of #of neuneu

#val #val ee

coppercopper 2929 2929 3434 11

aluminualuminumm

1313 1313 1414 33

germaniugermaniumm

3232 3232 4141 44

Electrical Classifications of Material:• the number of valence electrons is a common indication that tells us the electrical characteristics of a material.

•Conductor – material with less than four valence electrons. Conductors allow electrical current to flow easily because they have more free electrons.

•Insulator – material with more than four valence electrons. Insulators will not allow electrical current to flow easily because they have few or even no free electrons.

•Semiconductor – with exactly four valence electrons. Semiconductors have electrical characteristics in between conductors and insulators.

► Energy bandsEnergy bands Before a valence electron can escape from its Before a valence electron can escape from its

shell and becomes free, it must gain energy of at shell and becomes free, it must gain energy of at least equal to the energy gapleast equal to the energy gap►Energy gap – the energy difference between the Energy gap – the energy difference between the

valence band and conduction band. Its unit is the valence band and conduction band. Its unit is the electron volt (eV)electron volt (eV)

1eV = 1.6 x 101eV = 1.6 x 10-19 -19 JouleJoule► A unit of energy equal to the energy gained by an A unit of energy equal to the energy gained by an

electron in passing from a point of low potential to a electron in passing from a point of low potential to a point one volt higher in potential.point one volt higher in potential.

►Valence band – the region where the valence shell and Valence band – the region where the valence shell and valence electrons are occupying. It is the highest valence electrons are occupying. It is the highest energy level before conduction band.energy level before conduction band.

►Conduction band – the region where free electrons are Conduction band – the region where free electrons are said to be present . Electrons a this band have a higher said to be present . Electrons a this band have a higher energy level than those electrons at the valence band.energy level than those electrons at the valence band.

►Forbidden band – the region in an atom where no Forbidden band – the region in an atom where no electrons exist. It is in between two allowed bands, such electrons exist. It is in between two allowed bands, such as between valence and conduction bands.as between valence and conduction bands.

Nucleus Ground State

Forbidden Band

1st energy level

Valence band

Forbidden Band

Conduction band

Highest energy level

Energy gap (Eg)

Valence shell level

Levels bet.1st energy level & valence band

1st shell closest to the nucleus

electrons

Incr

easi

ng e

nerg

y level

Energy Band Diagram of an Atom

Energy gap (Eg) of :Conductors = 0 eVInsulators > 5 eVSemiconductors = 1eV

Eg = 0 means that the valence electrons can easily become free. This explains why conductors have the most number of free electrons and can easily support electric current flow.

► Law of Conservation of Charge:Law of Conservation of Charge: The net charge of an isolated system remains constant. The net charge of an isolated system remains constant.

The only way to change the net charge of a system is to The only way to change the net charge of a system is to bring in charge from elsewhere, or remove charge from the bring in charge from elsewhere, or remove charge from the system. system.

► Law of Conservation of Charge-Energy:Law of Conservation of Charge-Energy: Electric charge is neither created nor destroyed but is Electric charge is neither created nor destroyed but is

transferred from one body to another.transferred from one body to another.► Ion – a charged bodyIon – a charged body► Anion – negatively charged ionAnion – negatively charged ion► Cation – positively charged ionCation – positively charged ion► Electropositive elements are elements that give up Electropositive elements are elements that give up

electrons in chemical reactions to produce positive electrons in chemical reactions to produce positive ions. These elements are metallic in nature.ions. These elements are metallic in nature.

► Electronegative elements are elements that accept Electronegative elements are elements that accept electrons in chemical reactions to produce negative electrons in chemical reactions to produce negative ions. These elements are nonmetallic in nature.ions. These elements are nonmetallic in nature.

► Electric Field and Electric ForceElectric Field and Electric Force When the body is electrically charged, it is said to have When the body is electrically charged, it is said to have

electric field in its surroundings. This field interacts with electric field in its surroundings. This field interacts with other charged bodies and will produce an electric force that other charged bodies and will produce an electric force that may cause them to move. may cause them to move.

Electric fieldElectric field – – is the area or region surrounding an electrically is the area or region surrounding an electrically charged particle or bodycharged particle or body

Electric forceElectric force – – the force produced due to the electric field of a the force produced due to the electric field of a charged particle or body.charged particle or body.

► Electric potentialElectric potential the ability of a charged body to do work on charged particles such the ability of a charged body to do work on charged particles such

as electronsas electrons Electric potential differenceElectric potential difference – – the difference between the the difference between the

capacities (potentials) of two charges to do work.capacities (potentials) of two charges to do work. Volt (V)Volt (V) – – the unit of potential difference. the unit of potential difference. A potential of one volt A potential of one volt

(1V) has the capacity to do one joule (1J) of work in moving one (1V) has the capacity to do one joule (1J) of work in moving one coulomb (1C) of charge.coulomb (1C) of charge. Named after the Italian physicist, Named after the Italian physicist, Alessandro Volta (1745-1827) Alessandro Volta (1745-1827)

V = W/Q V = W/Q where: w = work or energy in joules where: w = work or energy in joules Q = charge in coulombsQ = charge in coulombs

VoltageVoltage – – another name for potential difference.another name for potential difference. Electromotive force (emf)Electromotive force (emf) – – the electrical force that moves the electrical force that moves

the charged p;articles such as electrons (electron moving force). the charged p;articles such as electrons (electron moving force). The term emf is used interchangeably with potential difference and The term emf is used interchangeably with potential difference and voltage.voltage.

► Electric currentElectric current Any directional movement of electric charges such as electrons.Any directional movement of electric charges such as electrons. Current in gases and liquids – generally consist of flow of positive Current in gases and liquids – generally consist of flow of positive

ions in one direction together with a flow o f negative ions in the ions in one direction together with a flow o f negative ions in the opposite direction.opposite direction.

Current in solids – such as wires, consist of the flow of electrons, and Current in solids – such as wires, consist of the flow of electrons, and is a measure of the quantity of charge passing any point of the wire is a measure of the quantity of charge passing any point of the wire per unit of time. per unit of time. ► I = dQ/ dt C/s or Ampere, the intensity of electron flowI = dQ/ dt C/s or Ampere, the intensity of electron flow

Ampere (A) – the unit of electric current. Named in honor to the Ampere (A) – the unit of electric current. Named in honor to the French physicist and mathematician, Andre M. Ampere (1775 – French physicist and mathematician, Andre M. Ampere (1775 – 1836)1836)

Current density (J) – the current per unit cross-sectional area Current density (J) – the current per unit cross-sectional area ► J = I/A = ampere/mJ = I/A = ampere/m22

Closed Circuit – a path for current flowClosed Circuit – a path for current flow Open circuit – a path for current flow is cut or opened.Open circuit – a path for current flow is cut or opened. Short circuit – a path for current flow that bypasses a component or Short circuit – a path for current flow that bypasses a component or

sub-circuit, which may create an overload.sub-circuit, which may create an overload. Schematic diagram – a diagram that uses symbols for components to Schematic diagram – a diagram that uses symbols for components to

draw the circuits draw the circuits Pictorial diagram – a diagram using pictures of component to show Pictorial diagram – a diagram using pictures of component to show

the circuits.the circuits. Direct current – charges flow in one direction onlyDirect current – charges flow in one direction only Alternating current – the motion of electric charges is periodically Alternating current – the motion of electric charges is periodically

reversed.reversed. Conventional current flow – the flow of charge from positive to Conventional current flow – the flow of charge from positive to

negative.negative. Electron flow – the flow of charge from negative to positive.Electron flow – the flow of charge from negative to positive.

► Determine what is given in the problem, that is, the given scenario or Determine what is given in the problem, that is, the given scenario or situation. The schematic diagram is usually given for you to draw and situation. The schematic diagram is usually given for you to draw and identify the known and the unknown in the diagram.identify the known and the unknown in the diagram.

► Determine what is being asked by the problem, that is, identify the Determine what is being asked by the problem, that is, identify the problemproblem

► Determine the theories, principles, formulas related to the problem Determine the theories, principles, formulas related to the problem and the given scenarios or situationand the given scenarios or situation

► From the formulas that relates the known and the unknown, From the formulas that relates the known and the unknown, substitute the given values.substitute the given values.

► Write your solutions at the point of view of the reader, which means Write your solutions at the point of view of the reader, which means that it must be on a step-by-step process avoiding short cuts that that it must be on a step-by-step process avoiding short cuts that may lead to misunderstanding by the reader. may lead to misunderstanding by the reader.

► Write legibly, logically, and highlight your final answer.Write legibly, logically, and highlight your final answer.► Example:Example:

Given: Given: Find ?Find ? FormulaFormula SolutionSolution Answer inside a boxAnswer inside a box

► In your computations, the resolution or number of decimal places of In your computations, the resolution or number of decimal places of your computed numbers should be at least 2 decimal places more your computed numbers should be at least 2 decimal places more than the highest resolution number in the given data when not exact.than the highest resolution number in the given data when not exact.

► The final answer should have 1 decimal place more than the highest The final answer should have 1 decimal place more than the highest resolution number in the given data when not exact.resolution number in the given data when not exact.

A guide to solving problemsA guide to solving problems

► Sample Problems:Sample Problems:1.1. A positively charged dielectric has a charge of 2 A positively charged dielectric has a charge of 2

coulombs. If 12.5 x 10coulombs. If 12.5 x 101818 free electrons are added to it, free electrons are added to it, what will be the net charge on the said dielectric? what will be the net charge on the said dielectric?

QQ11= +2C= +2CQQ22= -12.5 * 10= -12.5 * 101818e * (1C/6.25 * 10e * (1C/6.25 * 101818e) = -2Ce) = -2CQQnetnet= Q= Q11+Q+Q22 = 2 + (-2) = 2 + (-2)

QQnetnet= 0= 0 2.2. A battery can deliver 10 joules of energy to move 5 A battery can deliver 10 joules of energy to move 5

coulombs of charge. What is the potential difference coulombs of charge. What is the potential difference between the terminals of the battery?between the terminals of the battery?

Note: volt = joules per coulombNote: volt = joules per coulombE = W/Q = 10/5E = W/Q = 10/5E = 2 voltsE = 2 volts

3.3. A cloud of 2.5 x 10A cloud of 2.5 x 101919 electrons move past a given point electrons move past a given point every 2 seconds. How much is the intensity of the every 2 seconds. How much is the intensity of the electron flow?electron flow?

Note: ampere = coulombs per secondNote: ampere = coulombs per secondQ = (2.5 * 10Q = (2.5 * 101919) * 1C/(6.25 * 10) * 1C/(6.25 * 101818) = 4C) = 4CI = Q/t = 4/2I = Q/t = 4/2I = 2 amperesI = 2 amperes

Sample ProblemsSample Problems

4.4. The current in an electric lamp is 5 The current in an electric lamp is 5 amperes. What quantity of electricity flows amperes. What quantity of electricity flows towards the filament in 6 minutes?towards the filament in 6 minutes?

Q = It = 5(6min * (60sec/1min))Q = It = 5(6min * (60sec/1min))

Q = 1800 CQ = 1800 C

5.5. A consistent current of 4 A charges a A consistent current of 4 A charges a capacitor. How long will it take to capacitor. How long will it take to accumulate a total charge of 9 coulombs accumulate a total charge of 9 coulombs on the plates?on the plates?

t = Q/I = 8/4t = Q/I = 8/4

t = 2 sect = 2 sec

Exercises:Exercises:

1. Perform the following conversions:a. 27 minutes to seconds b. 0.8 hours to secondsc. 2 h 3 min 47 s to s d. 35 horsepower to wattse. 1827 W to hp f. 23 revolutions to degrees

2. Convert the following:a. 156 mV to volts b. 0.15 mV to microvoltsc. 47 kW to watts d. 0.057 MW to kilowattse. 3.5104 volts to kilovolts f. 0.0000357 amps to microamps

4. Positive charges Q1 2 mC and Q2 12 mC are separated center to center by 10

mm. Compute the force between them. Is it attractive or repulsive?5. Two equal charges are separated by 1 cm. If the force of repulsion between them is 9.7 102 N, what is their charge? What may the charges be, both positive, both negative, or one positive and one negative?6. After 10.61 1013 electrons are added to a metal plate, it has a negative charge of 3 mC. What was its initial charge in coulombs?

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Special AssignmentSpecial Assignment

► Research & Report Different Sources of Electricity Research & Report Different Sources of Electricity (deadline - next week)(deadline - next week) Report on AC sourcesReport on AC sources Report on DC sourcesReport on DC sources Content:Content:

► Source of Electricity – Description Source of Electricity – Description ► How it generates electricity?How it generates electricity?

Equipment/ parts/ composition involve, etc.Equipment/ parts/ composition involve, etc. Energy conversion to electrical energy – process Energy conversion to electrical energy – process

► Control of electricityControl of electricity Transmission and DistributionTransmission and Distribution Safety, Length of Life, etc.Safety, Length of Life, etc.

► Research & Report about Superconductors Research & Report about Superconductors (deadline – next week)(deadline – next week)