Complete Gibilisco

8/10/2019 Complete Gibilisco

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CHAPTER 1: BASIC PHYSICAL CONCEPTS

ATOMS

All matter is made up of countless tiny particles whizzingaround.

Each element has its own unique type of particle,known as its atom .

Atoms of different elements are always different. The slightest change in an atom can make a

tremendous difference in its behavior.

NUCLEUS

The part of an atom that gives an element its identity Made up of two kinds of particles, the proton and the

neutron.

PROTONS AND NEUTRONS

About the same mass , but the proton has an electriccharge while the neutron does not.

The negative charges therefore exactly cancel out thepositive ones, and the atom is electrically neutral .

ATOMIC NUMBER

Gives the element its identity. As the number of protons increases , the number ofneutrons also increases .

Elements with high atomic numbers are much denserthan elements with low atomic numbers.

ISOTOPES

The number of neutrons can vary but the elementkeeps its identity, based on the atomic number.

Differing numbers of neutrons result in various isotopesfor a given element.

ATOMIC WEIGHT

Approximately equal to the sum of the number ofprotons and the number of neutrons in the nucleus.

ELECTRONS

An electron has exactly the same charge quantity as aproton, but with opposite polarity .

One of the earliest ideas about the atom is like raisins in a cake .Later, the electrons were seen as orbiting the nucleus, makingthe atom like a miniature solar system with the electrons as theplanets.

SHELLS

Spheres where the electron are orbiting.

The farther away from the nucleus the shell, the moreenergy the electron has.

In any case, it is far easier to move electrons than it is to moveprotons. Electrons are much lighter than protons or neutrons.

IONS

If an atom has more or less electrons than neutrons,that atom acquires an electrical charge.

A shortage of electrons results in positive charge An excess of electrons gives a negative charge. The elements identity remains the same, no matter

how great the excess or shortage of electrons.

COMPOUNDS

Different elements join together to share electrons Compounds often, but not always, appear greatly

different from any of the elements that make them up.

MOLECULES

The resulting particles when atoms of elements join

together to form a compound. The natural form of an element is also known as itsmolecule.

CONDUCTORS

A substance in which the electrons are mobile.

Pure Elemental Silver is the best conductor at room temperature

Copper and aluminum are also excellent electrical conductors.

Iron, steel, and various other metals are fair to good conductorsof electricity.

In most electrical circuits and systems, copper or aluminum wire

is used. Silver is impractical because of its high cost.

Liquid:Mercury is a good electrical conductor.Salt water is a fair conductor.

Gases are poor conductors of electricity because the atoms ormolecules are usually too far apart to allow a free exchange ofelectrons.

INSULATORS

An insulator prevents electrical currents from flowing.Most gases are good electrical insulators.

Pure water is a good electrical insulator, although it conductssome current with even the slightest impurity.

IONIZATION

Ionization takes place when electrical insulators areforced to carry current.

DIELECTRIC

An insulating material is sometimes called a dielectric. It keeps electrical charges apart, preventing the flow of

electrons that would equalize a charge differencebetween two places.

Porcelain or glass can be used in electrical systems to keep short

circuits from occurring.

RESISTORS

Allow for the control of current flow. Electrical resistance is measured in units called ohms. The greater the resistance, the more difficult it

becomes for current to flow.

In an electrical system, it is usually desirable to have as low aresistance, or ohmic value, as possible. This is because resistanceconverts electrical energy into heat.

SEMICONDUCTORS


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In a semiconductor, electrons flow, but not as well as

they do in a conductor. Semiconductors are not exactly the same as resistors,

the material is treated so that i t has very specialproperties.

HOLE

A shortage of an electron. Holes move in the opposite direction from electrons in a

semiconducting material. When most of the charge carriers are electrons, thesemiconductor is called N-type, because electrons arenegatively charged.

When most of the charge carriers are holes, thesemiconducting material is known as P-type becauseholes have a positive electric charge.

The more abundant type of charge carrier is called themajority carrier.

The less abundant kind is known as the minority carrier .

CURRENT

Whenever there is movement of charge carriers in asubstance, there is an electric current.

Current is measured in terms of the number of electronsor holes passing a single point in one second.

A coulomb is equal to approximately6,240,000,000,000,000,000 electrons or holes.

*six quintillion ( 6 followed by 18 zeroes* quadrillions (numbers followed by 15 zeroes)

AMPERE

The standard unit of electric current. Current of one coulomb per second is called an

ampere.

STATIC ELECTRICITY

An excess or shortage of electrons is created on and inyour body. You acquire a charge of static electricity.

Its called static because it doesnt go anywhere.You dont feel this until you touch some metallic objectthat is connected to earth ground or to some largefixture; but then there is a discharge, accompanied bya spark.

Van de Graaff generator is a machine that an create a chargebuildup large enough to produce a spark several centimeterslong.

ELECTROMOTIVE FORCE

When the charge builds up, with positive polarity (shortage ofelectrons) in one place and negative polarity (excess ofelectrons) in another place, a powerful electromotive forceexists.

It is often abbreviated EMF. This force is measured in units calledvolts .

Ordinary household electricity has an effective voltage ofbetween 110 and 130; usually it is about 117. A car battery hasan EMF of 12 volts (six volts in some older systems).

An EMF of 1 volt, across a resistance of 1 ohm, will cause acurrent of 1 ampere to flow. This is a classic relationship inelectricity, and is stated generally as Ohms Law.

Voltage, or EMF, is sometimes called potential or potentialdifference.

VISIBLE LIGHT

Converts electricity into radiant energy that you can

see.

PHOTOVOLTAIC CELL

Visible light is converted into electric current orvoltage.

HEAT

A form of radiant energy called infrared. It is similar tovisible light, except that the waves are longer and youcant see them.

Electricity can also be converted into other radiant-energyforms, such as radio waves, ul traviolet, and X rays.

Generator

When a conductor moves in a magnetic field, electriccurrent flows in the conductor.

Converts mechanical energy into electricity.

Motor

Changes electricity into useful mechanical energy.

MAGNETISM

The science of magnetism is closely related toelectricity.

Magnetic phenomena are of great significance inelectronics.

The oldest and most universal source of magnetism isthe flux field surrounding the earth, caused byalignment of iron atoms in the core of the planet.

ELECTROMAGNETISM

A changing magnetic field creates a fluctuatingelectric field, and a fluctuating electric field producesa changing magnetic field.

CHEMICAL ENERGY

Converted into electricity in all dry cells, wet cells, andbatteries.

Your car battery is an excellent example. The acidreacts with the metal electrodes to generate anelectromotive force.

CHARGING

Then it runs out of juice, and the supply of chemicalenergy must be restored by charging.

Some cells and batteries, such as lead-acid carbatteries, can be recharged by driving current throughthem, and others, such as most flashlight and transistor-radio batteries, cannot.


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CHAPTER 2: ELECTRICAL UNITS

VOLT

Standard unit of electromotive force (EMF) or potentialdifference.

Potential difference between two points produces anelectric field, represented by electric lines of flux. (pole thatis relatively positive with fewer electrons and negative polewith more electrons)(p.18 fig2-1)

Abbreviation for volt is V. Dry cell voltage = 1.2 1.7 volts

Car battery = 12 14 voltsElectric lights = 117 voltsWashing machine, dryer, oven, stove = 234 volts

Largest voltages on our planet occur between clouds andthe ground, in thunderstorms.

Existence of voltage always means that charge carriers,which are electrons(e-) in a conventional circuit, flowbetween two points if a conductive path is provided.Voltage represents the driving force that impels chargecarriers to move.

CURRENT FLOW

It is the flow of electrons (e-). The flow of e- to equalize thecharge between poles.

It is the current , not the voltage that kills. There can only bea deadly current if there is enough voltage to drive itthrough your body.

Standard unit for current is Ampere. The amount of current that flows in an electrical circuit

depends on the voltage and also on the resistance (V=IR)

RESISTANCE

The measure of opposition that a circuit offers to the flow ofelectric current.

Ohms Law (V=IR) = current flow for a constant voltage issaid to be inversely proportional to the resistance.

CONDUCTANCE & SIEMENS

It is the reciprocal of resistance Unit is S for Siemens

G = 1/RR = 1/G1k ohm = 1m S1M ohm = 1uS

POWER AND THE WATTS

Whenever current flows through a resistance, heat results.Heat can be measured in watts(W) and representselectrical power.

P = EIP = VI

I = P/VV = P/I

ENERGY AND WATT-HOUR

Energy is power dissipated over a length of time Power is the rate at which energy is expended.

ENERGY UNITS

Mostly used is joules Page 27 Figure 2-3

In terms of joules:British thermal unit (Btu) = 1055Electron volts (eV) = 1.6X10 -19 Ergs = 0.0000001 / 10 -7 Foot-pounds(ft-lb) = 1.356Watt-hours = 3600Kilowatt- hours= 3,600,000 / 3.6x10 -6

ALTERNATING CURRENT AND HERTZ

Effective voltage for an ac wave is never the same as theinstantaneous maximum, or peak voltage. (p.28 fig.2-8)

Effective value is 0.70707 times the peak value. Or 1.414times the effective value

The instantaneous voltage is the voltage at any particularinstant in time.

Whole cycle repeats itself every 1/60 second, the

frequency of the utility ac wave is said to be 60 hertz Hertz literally translate to cycles per second

RECTIFICATION AND PULSATING DIRECT CURRENT

Rectification is a process in which ac is changed to dc Common method of doing this uses a device called the

diode. The point is that part of the ac wave is either cut off, or

turned around upside down, so the output is pulsating dc. There are two different forms of waveforms of pulsating dc.

(refer to p.29 fig 2-10).1. Half wave rectification2. Full wave rectification

Peak voltage is the maximum instantaneous voltage. Instantaneous voltage is never any greater than the peak

voltage for any wave.

MAGNETISM

Electric current and magnetic fields are closely related. When an electric current flows which i s when charge

carriers move a magnetic field accompanies thecurrent.(p.30 fig 2-11)

Magnetic fields are produced when the atoms of certainmaterials align themselves. Iron is the most common metalthat has this property.

The intensity of a magnetic field can be greatly increasedby placing a special core inside of a coil. Should be of ironor some other material that can be readily magnetized,such substance are ferromagnetic.

A core of this kind cannot actually increase the totalquantity of magnetism in and around a coil, but i t will

cause the lines of flux to be much closer together inside thematerial. Magnetic flux of lines are said to emerge from the

magnetic pole, and to run i nward toward the magneticsouth pole.

MAGNETIC UNITS

Overall magnitude of a magnetic field i s measured in unitscalled Webers(Wb)1 weber = 1 volt-second( 1 Vs)

For weaker magnetic fields, a smaller unit calledmaxweel(Mx) is used.

1 maxwell = 0.00000001 (1 hundredmillionth) of a weber or 0.01microvolt-second( 0.01uVs)

Flux density of a magnetic field is given in terms of webersor maxwells per square meter or per square centimeter.1 Wb/m 2 is called Tesla (1T)1 Mx/cm 2 is called gauss (1G, 0.0001 T)

As the electric current through a wire increases, so doesthe flux density near the wire.

A coiled wire produces a greater flux density for a givencurrent than a single, straight wire.

The more turns in the coil, the stronger the magnetic fieldwill be.

A magnetic field strength maybe specified in terms ofampere-turns (At). Unit of a magnetomotive force.

One loop carrying 1A of current, produces a field of 1 At. Doubling the number of turns, or the current, doubles the

number of ampere-turns.


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Less common unit of magnetomotive force is gilbert(Gb).This unit is equivalent of 0.796 At. 1 At=1.26 Gb

CHAPTER 3: MEASURING DEVICES

* Galvanometer * Electroscope * Ammeter (milli, micro) * Electrostatic meter * Voltmeter * Ohmmeter * Multimeter * FET voltmeter

* Wattmeter * Watt-hour meter * Frequency Counter * VU meter * light meter * Oscilloscope

A galvanometer is a type of ammeter: an instrument fordetecting and measuring electric current.

Galvanism -it is the induction of electrical current

Eletroscope - The most common device for demonstratingelectrostatic force

Ammeter - is a measuring instrument used to measure theelectric current in a circuit. ( It i s placed in series with one ofthe device on the circuit)

Electrostatic meter - Can detect ac as well as dc voltages

voltmeter - is an instrument used for measuring theelectrical potential difference between two points in anelectric circuit (Place in parallel)

* Voltmeter should have a high internal resistance *

FET voltmeter - It draws less current from the circuit

Multimeter - also known as a volt/ohm meter or VOM, is anelectronic measuring instrument that combines severalmeasurement functions in one unit. A typical multimetermay include features such as the ability to measure

voltage, current and resistance. Wattmeter - The wattmeter is an instrument for measuring

the electric power (or the supply rate of electrical energy)in watts of any given circuit.

Watt-hour meter - is a device that measures the amount ofelectrical energy consumed by a residence, business, oran electrically-powered device.

Frequency Counter - i s an electronic instrument, orcomponent of one, that is used for measuring frequency.

VU meter - is often included in audio equipment to displaya signal l evel in Volume Units; the device i s sometimes alsocalled volume indicator (VI).

light meter - is a device used to measure the amount oflight. also known as illumination meter.

Oscilloscope - is a type of electronic test instrument thatallows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potentialdifferences (vertical(Y) axis) plotted as a function of timeor of some other voltage (horizontal(x) axis).

Hot wire ammeter - A device capable of measuring ac.dccurrents

D'arsonval movement - An action caused byelectromagnetic deflection, using a coil of wire and amagnetized field. When current passes through the coil, aneedle is deflected.

In a simple ammeter, an electromagnet can be useinstead of permanent magnet

A resitor is connected across the ammeter if it is necessaryto measure very large amount of current. also known asshunt resistance or meter shunt.

"Dont leave voltmeter constantly connected to the circuit",it will affect the behavior of the circuit due to the resistanceof the voltmeter.


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CHAPTER 4: BASIC DC CIRCUITS

Wiring Diagram is more detailed than Schematic

Voltage/Current/Resistance Circuit Calculations

Ohms Law triangle.

NOTE: Wag kalimutang i-take into consideration ang mga PREFIX!

Power Calculations

Resistances in series : Add directly!

Resistance in Parallel: Get the ReciprocalAdd

Get the Reciprocal Again

For Parallel Resistors having the same values , just divide one value bythe number of resistors.

Example: May 4 resistors connected in parallel each having a value5 k . Total resistance = 5 k 4 = 1.250 k

Division of Power

Total Power Load = Evenly distributed among theresistances of the circuit if they have the same ohmicvalues .

Construction of Series Parallel Matrix (Resistances)-To increase the power handling capacity

Conditions to consider :--Identical resistors should be used!--(n) x (n) x (power rating) = total power capacity--Consider the resistances youre going to need i.e. #18 -- Most likely n x n is better than n x m due to resistance issues i.e.

#17

Chapter 5: Direct-Current Circuit Analysis

Ohms Law: V = IR Power, P = VI

Current through Series Resistances*The current in a series circuit is the same at every pointalong the way.

Voltages across Series Resistances*The voltages across elements in a series circuit always addup to the supply voltage.

Voltage across Parallel Resistances*In a parallel circuit, the voltage across each component isalways the same and it is always equal to the supply orbattery voltage.

Currents through Parallel Resistances*The currents through elements in a parallel circuit alwaysadd up to the total current drawn from the supply.

Conventional/Theoretical Current Flow

*Current flows from the positive to the negative voltagepoint.

Power Distribution in Series CircuitsP = I2RPower Distribution in Parallel CircuitsP = V 2/R

*The total power consumed in a series or parallel circuit is alwaysequal to the sum of the wattages dissipated in each of the elements.

Kirchhoffs First Law (Kirchhoffs Current Law, KCL) *Conservation of Current: At any node (junction) in anelectrical circuit, the sum of currents flowing into that nodeis equal to the sum of currents flowing out of that node.

Kirchhoffs Second Law (Kirchhoffs Voltage Law, KVL) *Conservation of Voltage: The sum of the EMFs in anyclosed loop is equivalent to the sum of the potential dropsin that loop.

Voltage Divider Networks*The voltage divider fixes the intermediate voltages bestwhen the resistance values are as small as the current-delivering capability of the power supply will allow.


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CHAPTER 6: RESISTORS

PURPOSE OF THE RESISTOR:

1. Voltage Division

The resistors dissipate some power but the resultingvoltages can provide the proper biasing of electronic

circuits. For example, an amplifier or oscillator will function inthe most efficient and reliable way possible.

2. Bias

Bias, in the case of bipolar transistor, a field-effecttransistor or a vacuum tube, that the controlelectrode - the bias, gate or grid is provided with acertain voltage, or carry a certain current, relative tothe emitter, source or cathode.

3. Current Limiting

Resistors interfere with the flow of electrons in a circuit. This is essential to prevent damage to a component or

circuit. A good example is in a receiving amplifier. A resistor

can keep the transistor from using up a lot of power just getting hot.

4. Power Dissipation

In radio, a resistor can be used to take the place of anantenna. A transmitter can then be tested in such away that it doesnt interfere with signals on theairwaves. The transmitter output heats the resistor,without radiating any signal.

The circuit driving the amplifier has too much power

for the amplifier input. A resistor, or network of resistors,can dissipate this excess so that the power amplifierdoesnt get too much drive.

5. Bleeding Off Charge

Bleeder resistors, connected across the filtercapacitors, drain their stored charge so that servicingthe supply is not dangerous.

6. Impedance Matching

In order to produce the greatest possibleamplification, the impedances must agree betweenthe output of a given amplifier and the input of thenext.

FIXED RESISTORS

Units whose resistance does not change, or cannot beadjusted.

1. Carbon-Composition Resistors

Carbon-composition resistors can be made to havequite low resistances, all the way up to extremely highresistances.

Nonreactive - introduces almost pure resistance intothe circuit, and not much capacitance orinductance.

Useful in radio receivers and transmitters.

Most of the carbon-composition resistors can handle 14 W or 1/2 W.

2. Wirewound Resistors

The resistance is determined by how well the wiremetal conducts, by its diameter or gauge, and by itsstretched-out length.

Precision Components. Can handle large amount of power. Disadvantage: Act like inductors. Low moderate Values of resistance.

3. Film-Type Resistors Metal-film resistors can be

made to have nearly exactvalues.

Low to medium resistance. Advantage: Do not much

have inductance orcapacitance.

Disadvantage: Cant handle as much power ascarbon-composition or wirewound types.

4. Integrated-Circuit (IC) Resistors Resistors can be fabricated on a semiconductor

wafer known as an IC also called a chip.


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Can handle only a tiny amount of powerbecause of their small size.

THE POTENTIOMETER

1. Linear-Taper Potentiometer

One type of potentiometer uses a strip of resistive materialwhose density is constant all the way around.

The resistance between the center and one end terminalwill increase right along with the number of angulardegrees that the shaft is turned.

Linear taper potentiometers are commonly used inelectronic test instruments and in various consumerelectronic devices.

2. Audio-Taper Potentiometer

The resistance between the center and the end terminalincreases as a nonlinear function of the angular shaftposition.

Also called logarithmic-taper potentiometer or log-taperpotentiometer.

3.

The Rheostat A variable resistor made from a wire wound element. Either have a rotary control or a sliding control. Rheostat can be placed between the utility outlet and the

transformer. This results in a variable voltage at the power-supply output.

THE DECIBEL

RESISTORS SPECIFICATIONS

Ohmic Value

Tolerance

Power Rating Temperature Compensation The Color Code for Resistors

dB= 10 log (Q/P)Q = P antilog (dB/10)


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CHAPTER 7: CELLS AND BATTERIES

CELL a unit source of DC energy.

BATTERY two or more cells connected in series.

ELECTROCHEMICAL ENERGY

Voltages appeared between pieces of metal whencame into contact with certain chemical solutions.

Chemicals and the metals have an inherent ability to

produce a constant exchange of charge carriers. Note: The chemical energy in a battery or cell changes

to electrical energy when the cell is used.

PRIMARY CELLS

electrical cells which chemical energy has all beenchanged to electricity and used up must be thrownaway and cannot be recharged.

i.e. batteries used in flashlight or transistor radio; AAAbatteries, D batteries, watch and camera batteries, 6-Vlantern batteries [dry cell, zinc-carbon cell or alkalinecell]

SECONDARY CELLS

cells that can get chemical energy back by means of recharging.

i.e. A, C or D batteries, car batteries [nickel-based cells]

WESTON STANDARD CELL

produces 1.018V at room temperature. *generally used as voltage reference source

STORAGE CAPACITY

Ampere-hours (Ah) unit of electrical energy in a cell. Shelf life length of time the battery will last if it is never

used. Maximum deliverable current highest amount of

current that the battery can provide before its voltagedrops because of its own internal resistance .

Small cells: 100-200 mAh Medium-sized cells: 500 mAh to 1Ah Large automotive or truck batteries: 50Ah and up **A direct short-circuit of a large battery can cause a

physical rupture or explosion.

Note: The energy in a cell or battery depends mainly onits physical size .

AAA very small AA small C medium large D large

ZINC-CARBON CELLS

Inexpensive good at moderate temperature and not very good in

extreme cold good in applications where the current drain is

moderate to high

ALKALINE CELLS

can work at lower temperatures than a zinc-carboncell

lasts longer in most electronic devices preferred for use in transistor radios, calculators and

portable cassette players

shelf life is much longer than zinc-carbon costs more

TRANSISTOR BATTERIES

consists of 6 zinc-carbon or alkaline cells in series thatsupplies 1.5V each. Thus, the battery supplies 9V.

used in low-current electronic devices preferred for use in remote-control garage door

openers, TV and hi-fi remote controls and electroniccalculators

*The voltage produced by a battery of multiple cellsconnected in series is more than the voltage producedby a cell of the same composition.

LANTERN BATTERIES

has much greater mass than a common dry cell ortransistor battery

lasts much longer deliver more current usually rated 6V good for scanner radio receivers in portable

locations(two-way portable radio), camping lamps,and other medium-power needs

MINIATURE CELLS AND BATTERIES

used in wristwatches, small cameras, and variousminiature electronic devices

SILVER-OXIDE CELLS AND BATTERIES

buttonlike shape and can fit inside a small wristwatch cells supply 1.5V cells can be stacked up to make batteries that can

provide 6, 9 or 12V used for transistor radio and other light-duty electronic

devices

MERCURY CELLS AND BATTERIES

properties similar to silver-oxide cells supply 1.35V when dead, they must be discarded because mercury

is toxic to human and animals

LITHIUM CELLS AND BATTERIES

cells supply 1.5-3.5V used for memory backup for electronic

microcomputers, LCD watch or clock have superior shelf life; can last for years in very low

current applications

LEAD-ACID BATTERIES

rechargeable

used in consumer electronic devices that requiremoderate amount of current

ie. Uninterruptible power supply (UPS) that can keep aPC running for a few mins when power fails

automotive battery is a large lead-acid battery not expensive

NICKEL-BASED CELLS AND BATTERIES

rechargeable cylindrical cells ordinary dry cells button cells used in watches, cameras, memory

backup flooded cells used in heavy-duty applications; storage

capacity in excess of 1000Ah


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spacecraft cells **Never discharge nickel-based cells all the way until

they totally die

PHOTOVOLTAIC CELLS AND BATTERIES

converts visible light, infrared (IR) and/or ultraviolet (UV)directly into electric current

SOLAR PANELS

photovoltaic cells combined in series-parallel often very large; consist of 50x20 cells

series scheme boosts the voltage to desired level parallel scheme increases the current-delivering ability

of the panel used in satellites can be used in conjunction with rechargeable

batteries to provide power in commercial utilities interactive solar system allows a homeowner to sell

power to the electric company

FUEL CELLS

HYDROGEN FUEL

hydrogen combined with oxygen hydrogen oxidizes at a lower temperature proton exchange membrane (PEM) is widely used and

generates approximately 0.7Vdc

METHANOL

advantage of being easier to transport and store thanhydrogen

PROPANE

stored in liquid in tanks; used in heating system METHANE natural gas


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CHAPTER 8: MAGNETISM

Geomagnetic Field

earths core made up of iron and has poles.

North geomagnetic pole

located far northern Canada

South geomagnetic pole

located near Antarctica

Geomagnetic axis

relative to the axis on w/c earth rotates.

Solar wind

stream of particles from the sun that distort thegeomagnetic lines of flux (sun ejects protons & heliumnuclei constantly which is a positive electric charge)Fig. 8-1

Lode stones

rock used in ancient times as a navigating tool

Magnetic compass

needle tries to align parallel to the lines of flux

*geomagnetic inclination and geomagnetic declination

Ferromagnetic material

(iron,nickel & alloys) stick to magnets and can bepermanent magnets.

Magnetic force

magnet is brought near a ferromagnetic material,atoms lined-up and the material temporarilymagnetized

Attraction and repulsion

force gets stronger as the magnets are brought neareach other.

Magnetic field

occurs when ferromagnetic materials are aligned;caused by the motion of electric charge carriers, eitherin wire or free space.

Solar flare

sun ejects far more charged particles than normal anddisrupts the geomagnetic field.

Geomagnetic storm

disruption of geomagnetic field w/c causes the earthsionosphere to change and affect long distance radiocomm. At certain frequency

Flux lines

determines the intensity of a magnetic field*bar magnet- N to S Fig. 8-2*current-carrying wire- circles around the wire Fig. 8-3

Electric monopole

a charged particle, such as proto or electron hoveringall by itself in space

Electric lines of flux

charged particle in free space are straight and run offto infinity Fig. 8-4

Magnetic dipole a pair of magnetic poles

Magnetic field strength

Webers(Wb) *strong; Maxwell(Mx) *weak

1Wb = 10 8Mx ; 1Mx = 10 -8 Mx

Tesla and gauss

concentration or intensity of magnetic field w/ in acertain cross section

Flux density

no. Of lines per square meter or per square cm

1Tesla(T) = 1Wb/m 2 ; 1Gauss(G) = 1Mx/cm 2 1G = 10 -4 T ; 1T = 10 4G

Ampere-turn(At)

unit of magnetomotive force and counterpart of emf

1Gb = 0.796At ; 1At = 1.26Gb

Electromagnet

type of magnet which produces a magnetic field with

the use of electric current *DC types- large bolt wrapping a few dozen of wirearound it with a battery to provide current Fig. 8-5

*AC types- wall outlet as a source; magneticlevitationFig. 8-6

Magnetic Properties of Materials

1.Ferromagnetism

when substance cause magnetic lines of flux to bunchcloser together.

2.Diamagnetism

when substance decreases the magnetic flux densityby causing the magnetic flux to diverge.

3.Permeability

indicator of extent to w/c a ferromagnetic materialconcentrates magnetic lines of flux.

4.Retentivity


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also called remanence; is a measure of how well thesubstance memorizes the magneti sm and becomesa permanent magnet.

Br= 100(y/x)% (y- current removed; x- current subjected)

Practical Magnetism

1. Permanent Magnets

manufactured using a high-retentivity ferromagnetic

material.

2. Ringer Device

bell ringer or chime Fig. 8-7 main component called solenoid

3. Relay

remote control switching of high current circuits Fig. 8-8

4. DC motor

converts DC energy to rotating mechanical energy attraction of opposite pole and repulsion of like poles;

constant torque Fig. 8-9

Armature coil set of coils rotate w/ the motor shaft

Field coil- stationary

Commutator

keeps the rotational force going in the same angulardirection to rotate not to oscillate.

5. Magnetic Tape

recording head which polarizes the ferro-particles

6. Magnetic Disks

hard drives which stores the most data, found insidethe computer

7. Bubbling Memory

sophisticated method of storing data a type of non-volatile computer memory that uses a

thin film of a magnetic material to hold smallmagnetized areas, known as bubbles or domains ,each of which stores one bit of data.
http://en.wikipedia.org/wiki/Non-volatile_memoryhttp://en.wikipedia.org/wiki/Computer_memoryhttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Computer_memoryhttp://en.wikipedia.org/wiki/Non-volatile_memory


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CHAPTER 9: ALTERNATING CURRENT

Characteristics of AC

1. polarity reverses again and again at regular intervals. 2. Amplitude varies 3. Frequemcy-dependent

PERIOD AND FREQUENCY

PERIOD (T)

the length of time between one repetition of thepattern, or one cycle, and the next

FREQUENCY(f)

cycles per second (cps)Hertz(Hz)1 cps = 1 Hz

Relationship between Period and Frequency

Pure

ac waves that have only one frequency

Fundamental: ac waves that have components atmultiples of the main.

THE SINE WAVE

Sine wave means that the direction of the currentreverses at regular intervals

current-versus time curve is shaped like thetrigonometric sine function.

SQUARE WAVES

an AC wave whose instantaneous amplitude remainsconstant even though the polarity reverses.

ASYMMETRICAL SQUARE WAVES

squared off wave that are lopsided.

SAWTOOTH WAVES

ac waves that rise and fall in straight lines as seen on anoscilloscope screen

Slope

indicates how fast the magnitude is changing

Three kinds of Sawtooth Waves

1. Fast-rise, slow-decay - The positive-going slope (rise) isextremely steep, as with a square wave, but thenegative-going slope (fall or decay) is gradual .

2. Slow-rise, fast-decay - sometimes called a ramp ,because it looks like an incline going upwards. It isuseful for scanning in television sets and oscilloscopes

3. Variable rise and decay - slopes in an infinite numberof different combinations.

Complex and irregular waveforms

As long as it has a definite period, and as long as thepolarity keeps switching back and forth betweenpositive and negative, it is ac.

Frequency spectrum

Oscilloscope

time domain instrument

Spectrum analyzer

frequency-domain instrument

Pure sine wave

single pip

Fundamental: contains harmonic energy along withenergy at the fundamental frequency.

FRACTIONS OF A CYCLE

1 cycle = 1 rev around a circle

Degrees

One method of specifying the phase of an ac cycle isto divide it into 360 equal parts, called degrees ordegrees of phase.

Starts at 0 where magnitude is zero and positive-goingand ends at 360.

Radians

A cycle can be divided into equal parts. 1 rad phase = rad = the angular frequency of a wave, in radians per

second, is equal to about 6.28 times the frequency inhertz.

PHASE DIFFERENCE

Composite wave produced by adding ac waves together

frequency amplitude phase Compositeoutput

identical identical Differ by180

Does not exist

identical Identical In phase Samefrequency;amplitude =twiceamplitude of


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either signalidentical Different Differ by

180Samefrequency;amplitude =differencebetween thetwo

identical Different identical Samefrequency;amplitude =sum betweenthe two

identical Different Differ byoddamount

Samefrequency;variety isinfinite

EXPRESSIONS OF AMPLITUDE

Amplitude

magnitude level, strength or intensity

Instantaneous amplitude

the amplitude at some precise moment in time. constantly changes

Peak amplitude

the maximum extent, either positive or negative, thatthe instantaneous amplitude attains.

Peak-to-peak amplitude

the net difference between the positive peakamplitude and the negative peak amplitude.

Root-mean-square amplitude

It literally means that the value of a wave ismathematically operated on, by taking the square rootof the mean of the square of all its values

Effective level of an ac wave

is the voltage, current or power that a dc source wouldhave to produce, in order to have the same generaleffect.

For a perfect sine wave,

rms value = 0.707 x peak value, or= 0.354 x pk-pk value

peak value = 1.414 x rms value pk-pk value = 2.828 x rms value

For a perfect square wave,

rms value = peak value pk-pk value = 2 x rms value or the peak value

Superimposed direct current

Sometimes a wave can have components of both acand dc

If the dc component exceeds the peak value of the acwave, then fluctuating, or pulsating, dc will result

THE GENERATOR

The ac voltage that a generator can develop dependson the strength of the magnet, the number of turns in

the wire coil, and the speed at which the magnet orcoil rotates.

The ac frequency depends only on the speed ofrotation.

for utility ac, this speed is 3,600 revolutions per minute(rpm), or 60 complete revolutions per second (rps), sothat the frequency is 60 Hz.

The efficiency of a generator is the ratio of the poweroutput to the driving power, both measured in thesame units multiplied by 100 to get a percentage.

Why AC?

Alternating current lends itself well to being transformedto lower or higher voltages, according to the needs ofelectrical apparatus


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CHAPTER 10: INDUCTANCE

INDUCTORS

electrical components that oppose the flow of AC bytemporarily storing energy as magnetic fields .

INDUCTANCE, L

directly proportional to the number of turns in a wire,and diameter and length of a coil

1H represents a potential difference of 1V across aninductor which the current is changing at the rate of1A/s

*Small coils w/ few turns of wire produce smallinductances, in which the current changes quickly

*Large coils w/ ferromagnetic cores and having manyturns of wire, current changes slowly

INDUCTORS IN SERIES

L = L1+L 2+L3++L n

INDUCTORS IN PARALLEL

1/L =1/ L 1+1/L 2+1/L 3++1/L n

COEEFICIENT OF COUPLING, k

ranges 0 (no interaction) to 1 (maximum possibleinteraction)

k=0 when two coils are separated by a sheet of solidiron or by a great distance

k=1 when two coils wound on the same form, one rightover the other

MUTUAL INDUCTANCE, M

M= k (L1L 2 )1/2

if two ac waves are in phase, the inductance isincreased

it two waves are in opposing phase the inductance isdecreased

*When two inductors are connected in series and there isreinforcing mutual inductance between them

L = L1+L 2+2M

* When two inductors are connected in series and there isopposing mutual inductance between them

L = L1+L 2-2M

AIR-CORE COILS

excellent efficiency used mostly in radio-frequency transmitters, receivers

and antenna networks *the higher the frequency of ac, the less inductance is

needed to produce significant effects By using heavy-gauge wire and making the radius of

the coil large, air-core coils have almost unlimitedcurrent-carrying capacity

disadvantage: low permeability

FERROMAGNETIC CORES

common at high and very high radio frequencies used at audio frequencies, as well as at low, medium

and high radio frequencies

has high permeability, causing a great concentrationof magnetic flux lines within the coil

smaller than air-core coils disadvantage: has potential for the core to saturate;

when a core becomes saturated, any further increasein coil current will not produce a correspondingincrease in the magnetic flux in the core

can also waste considerable power as heat making thecoil lossy

SOLENOIDAL COILS

used in adjusting frequency of a radio circuit can be made to have a variable inductance by sliding

ferromagnetic cores in and out of them controlled by ascrew shaft

moving the core further in the solenoidal coil increasesthe inductance

TOROIDS

advantage: fewer turns of wire are needed to get acertain inductance

: physically smaller for a given inductance and current-carrying capacity

: all the flux is contained within the core material reduces unwanted mutual inductances

disadvantage: difficult to permeability-tune : harder to wind : mutual inductance between or among physically

separate coils is actually desired

POT CORES

same advantages as toroids better than toroids if the main objective is to get a

large inductance in a small space disadvantage: tuning or adjustment of inductance is

impossible

FILTER CHOKES

large coil used to smooth out the pulsations in directcurrent that result when ac is rectified in a power supply

INDUCTORS AT AF

range in value of a few millihenrys up to about 1H

INDUCTORS AT RF

ranges from a few kilohertz to well above 100 Ghz. as the frequency increases, cores having lower

permeability are used

TRANSMISSION LINE INDUCTORS

used to get energy from one place to another

used at frequencies about 100Mhz

LINE INDUCTANCE

Scm =7500v/f


15/24

CHAPTER 11: CAPACITANCE

Capacitance

impedes the flow of ac charge carriers by temporarystoring the energy as an electric field

Property of Capacitance

Fig. 11-1 the size of the plate has a major factor; Fig. 11- 2 capacitor charge over a period of time

*Capacitance is directly proportional to the surfacearea of the conducting plates or sheets, and inverselyto the separation between conducting sheets

*the closer the sheets are to each other, the greaterthe capacitance

Unit of capacitance - ratio between the current thatflows and the rate of voltage change between theplates as the plate become charged

1 farad(1F)o - 1A while there is a voltage increase 1V/so 1V potential difference for an electric charge

of 1C.1 F = 10 -6 F ; 1 pF = 10 -12 F

Capacitors in Series:

1/C = 1/C 1 + 1/C 2 + 1/C 3 + . . . + 1/C n *net capacitance is roughly equal to the smallest

capacitance

If C1 = C 2 = C 3 = ... = C n ; C = C 1/n

Capacitors in Parallel:

C = C1 + C2 + C3 + ... + C n

Fixed Capacitors

has a value that cannot be adjusted and does not varywhen environmental or circuit conditions change

Dielectric materials

accommodate electric fields well, but poor conductorsof electric currents

good insulators Fig. 11-5

Paper Capacitors

placing a paper soaked w/ mineral oil between stripsof foil.

ranging about 0.001 F to 0.1F ; low to moderatevoltages up to about 1000V

Mica Capacitors

alternately stacking metal sheets & layers of mica Fig.11-6; main application for radio receiver andtransmitter

ranging little lower than paper capacitors ranging fromfew tens of pF up to 0.05F

Ceramic Capacitors

meshing & layering like mica, ranging from few pF toabout 0.5F ; voltage comparable to paper capacitors

disk ceramic capacitor- for small values only one layerof ceramic is needed & 2 metal plates glued to the diskshaped material on each side.

tubular capacitors- tube or cylinder of ceramics can beinside & outside of tube

Plastic-Film Capacitors plastics make good dielectrics for capacitors polyethylene & polystyrene are used, manufactured

same as paper capacitors range from 50pF to several tens of F , most often at

0.001F to 10F

Electrolytic Capacitors

provides greater capacitance, polarized component can have thousands of F & can handle thousands of

volts

Tantalum Capacitors

replacement for aluminium; used in militaryapplications because they almost never fail.

electrolytic capacitor

Semiconductor Capacitors

embedded on an IC or chips Fig. 11-7

Semiconductor Diode

conducts current in one direction, & refuse to conductin the other direction

*when a voltage source is connected across a diode so that it does not conduct, the diode acts as acapacitor.

*the greater the reverse voltage, the smaller thecapacitance

Variable Capacitors

adjusting the mutual surface area between the plates changing the spacing between the plates

Air Variables

connecting 2 sets of metal plates so that they mesh,and by affixing one set to a rotable shaft, Fig. 11-8

max capacitance depends on the no. Of plates &spacing between plates

common values 50-500pF

Trimmer Capacitors Fig. 11-9 few pF up to about 200pF

Coaxial Capacitors

TL < /4 acts as a capacitor. Capacitance increaseswith length Fig. 11-10

Capacitor Specifications

1. Tolerance

the lower the tolerance no. The more closely youexpect the actual component value to match therated value

2. Temperature Coefficient (%/ oC)

Positive temp. Coefficient - increase in value as thetemperature rises

Negative temp. Coefficient - decrease in value as thetemperature rises


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Zero temp. Coefficient - value remain constant within aspan of temperature

Interelectrode Capacitance

when two piece of conducting material are broughtnear each other

CHAPTER 12: PHASE

INSTANTANEOUS VALUES

+1V positive peak; negative going-1V negative peak; positive going

INSTANTANEOUS RATE OF CHANGE

The Graph 12.2 is the instantaneous rate of change of asine wave but is 1/4 phase difference than the originalsine wave, that makes is cosine.

VECTOR

Is a quantity with two independent properties calledmagnitude (amplitude) and direction .

Amplitude is independent of time. The vector lengthnever changes but its direction does.

PHASE DIFFERENCE

Also called phase angle . The Phase differencebetween two waves can have meaning only when twowaves have identical frequencies.

PHASE COINCIDENCE

Two waves begin at exactly the same moment but ofdifferent amplitudes.

Phase difference in this case is 0.

If two sine waves are in phase coincidence, the peakamplitude of the resultant wave, which will also be asine wave, is equal to the sum of the peak amplitudesof the two composite waves.

The phase of the resultant is the same as that of thecomposite waves.

PHASE OPPOSITION

Two waves begin exactly 180 apart.

INTERMEDIATE PHASE DIFFERENCE

0 and 360 phase coincidence 90 and 270 quadrature 180 phase opposition

LEADING

If wave X begins a fraction of a cycle earlier than waveY, then wave X is said to be leading wave Y in phase.

LAGGING

Imagine that wave X starts its cycle later than wave Y, by somevalue between 0 and 180 degrees. Then wave X is lagging,wave Y.


17/24

VECTOR DIAGRAMS OF PHASE DIFFERENCE

TIME Is represented by counterclockwise motion of both

vectors at constant angular speed.


18/24

CHAPTER 14: CAPACITIVE REACTANCE

The capacitive-reactance ray goes in a negativedirection and is assigned negative ohmic values.

Capacitors

Capacitive reactance, like inductive reactance,varies with frequency. But X C gets LARGER(negatively) as the frequency goes down.

Capacitive reactance is talked about in terms of i tsabsolute value, with minus sign removed.

The absolute value of X C increases as the frequencygoes down, or that the absolute value of X Cdecreases as the frequency goes up.

Capacitive Reactance and Frequency

Current Leads Voltage

In a circuit containing capacitive reactance, thevoltage lags the current in phase. Thus, current leadsvoltage.

PURE CAPACITANCE

XC is extremely largecompared with theresistance R.

Current leads thevoltage by just about90 o

CAPACITANCEANDRESISTANCE

f R is

smallcomparedwiththeabsolu

te value of X C, the difference is almost a quarter of acycle. As R gets larger, or as the absolute value of X Cbecomes smaller, the phase difference decreases.

A circuit containing resistance and capacitance iscalled an RC Circuit.

PURE CAPACITANCE

The absolute value of the capacitivereactance gets small enough, the circuit actsas a pure resistance, and the current is inphase with the voltage.

XC = -1/(2 f C)XC = -1/(6.28 f C)


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CHAPTER 15: IMPEDANCE AND ADMITTANCE

ADMITTANCE

the extent to which an ac circuit allows current flow,rather than impeding it.

Imaginary numbers

i is the . It is the number that, when multiplied by itself,gives 1. So i = j, and j x j =1.

In electronics, real numbers represent resistances.Imaginary numbers represent reactances.

Complex numbers

This term doesnt mean complicated; it would betterbe called composite.

Adding and subtracting complex numbers

The general formula for the sum of two complexnumbers ( a + jb ) and ( c + jd ) is

(a + jb ) + ( c + jd ) = ( a + c ) + j(b +d )

Multiplying complex numbers

The product of ( a + jb ) and ( c + jd ) is equal to(a + jb )(c + jd ) = (ac - bd ) + j(ad + bc )

The complex number plane

Absolute value

The absolute value of a complex number a + jb is thelength, or magnitude, of its vector in the complexplane, measured from the origin (0,0) to the point ( a ,b).

In the case of a pure real number a + j0, the absolutevalue is simply the number itself, a .

In the case of a pure imaginary number 0 + jb, theabsolute value is equal to b.

If the number is neither pure real or pure imaginary:

The RX plane

Resistances are represented by nonnegative realnumbers. Reactances, whether they are inductive(positive) or capacitive (negative), correspond toimaginary numbers.

Capacitors act like negative inductors

Vector representation of impedance

Any impedance R + jX can be represented by acomplex number of the form a + jb. Just let R =a and X=b.

Resistance is one-dimensional. Reactance is also one-dimensional. But impedance is two-dimensional.

Absolute-value impedance

the capital letter Z is used in place of the wordimpedance

If youre not specifically told what complex impedanceis meant when a single number ohmic figure is quoted,its best to assume that the engineers are talking aboutnonreactive impedances.

Characteristic impedance Characteristic impedance or surge impedance. It is

abbreviated Zo, and is a specification of transmissionline

Transmission lines

is required any time that it is necessary to get energy orsignals from one place to another

take either of two forms, coaxial or two wire

Factors affecting Zo

of the wires, spacing between the wires, The nature of the insulating material separating the

wires. diameter In general, Zo increases as the wire diameter

gets smaller, and decreases as the wire diameter getslarger, all other things being equal.

In a coaxial line, the thicker the center conductor, thelower the Zo if the shield stays the same size. If thecenter conductor stays the same size and the shieldtubing increases in diameter, the Zo will increase.

Impedance Matching

Is the process of making sure that the impedance ofthe load is purely resistive, with an ohmic value equal tothe characteristic impedance of the transmission lineconnected to it.

Conductance (G)

works the same way as it does in a dc circuit.G=1/R

Susceptance (B)

It is the reciprocal of reactance Can be either capacitive or inductive

BC = 1/ XC, and BL = 1/X L 1/j = -j and 1/-j = j

Admittance (Y)

Conductance and susceptance combine to formadmittance.

a complex quantity and represents the ease with whichcurrent can flow in an ac circuit

As the absolute value of impedance gets larger, theabsolute value of admittance becomes smaller

negative j factors mean that there is a net inductancein the circuit, and

positive j factors mean there is net capacitance.


20/24

CHAPTER 16: RLC AND GLC CIRCUIT ANALYSIS

RLC (Resistance-Inductance-Capacitance)

GLC (Conductance-Inductance-Capacitance)

RX (resistance-reactance) >> series ckt analysis

GB (conductance-admittance) >> parallel ckt analysis

Complex Impedances in Series

Z = (R1+R2) + j (X 1 + X 2)

Pure Reactances:

X = X L + X C

jXL = j2fL >> always positive jXC = - j / (2fC) >>always negative

Series resonance

for series-connected components, the condition inwhich the capacitive and inductive reactancescancel

Adding Impedance Vectors

*In reality, there is resistance, as well as reactance, inan ac series circuit containing a coil and capacitorbecause the coil wire has significa nt resistance (itsnever a perfect conductor) or because a resistor isdeliberately connected into the circuit.

Series RLC Circuits

*Resistance R can be imagined as belonging entirelyto the coil

Z = R + j (X L + X C)

Complex Admittances in Parallel

Y = (G 1+G 2) + j(B 1 + B2)

Pure Susceptances:

B = BL + BC

jBL = - j / (2fL) >>always negative jBC = j2fC >> always positive

Parallel resonance

for parallel-connected components (LC circuit), thecondition in which the capacitive and inductivesusceptances cancel

Parallel GLC Circuits

*The resistance is thought of as a conductance, whosevalue in Siemens (S) is equal to the reciprocal of thevalue in ohms. Also, the conductance is imagined tobelong to the inductor

Y = G + j (B L + BC)

Admittance to Impedance Conversion:

R = G / (G 2 + B2)X = B / (G 2 + B2)

1. Find the conductance G = 1/R for the resistor. (It will bepositive or zero.)

2. Find the susceptance B L of the inductor using theappropriate formula. (It will be negative or zero.)

3. Find the susceptance B C of the capacitor using theappropriate formula. (It will be positive or zero.)

4. Find the net susceptance B = BL + BC (It might be positive,negative, or zero).5. Compute R and X in terms of G and B using the

appropriate formulas.6. Assemble the vector R + jX.

Reducing Complicated RLC Circuits

Series CombinationR >> SeriesL >> SeriesC >> Parallel

Parallel CombinationR >> ParallelL >> Parallel

C >> Series

Impedance bridge

measures R and X at various frequencies

Ohms Law for AC Circuits

Purely Resistive Impedances

V = IZ

Complex Impedances

Series RLC: Z2 = R2 + X2 Parallel RLC: Z2 = R2X2 / (R 2 + X 2)

*Consider only the positive square root of the answer for Z

Note: In an RX ac circuit, there is always a difference in phasebetween the voltage across the resistance and the voltageacross the reactance. The voltages across the componentsalways add up to the applied voltage vectorially, but not alwaysarithmetically. It is also the same case for current computations.


21/24

CHAPTER 17: POWER AND RESONANCE IN AC CIRCUITS

What is power(P)?

Power is the rate at which energy is expanded,radiated or dissipated. (W,Kw,Mw,mW,nW)

Watt = joule/secP = EI

where E - volts

I - ampere

Then P is in volt-ampere (VA) or VA power or Apparent Powerinstantaneous power

The constant change in power

in a pure resistance circuit true power = V power If ac circuit contains reactance (inductive, capacitive)

VA > true power and the extra power is called"imaginary power" or "reactive power"

* In a circuit with inductive reactance, the current lagsthe voltage by up to 90 degrees

* In a circuit with capacitive reactance, the currentleads the voltage by up to 90 degrees

Power factor (PF)

ratio of true power to VA, Pt/Pva or PF= cos phaseangle

* If there is no reactance Pt = Pva therefore PF=1 * If there is no resistance and purely reactance Pt=o

then PF = 0

Phase angle

the extent to w/c the curent and voltage differ inphase

* If there is no reactance phase angle = 0 * If pure reactance phase angle = 90 and -90

elsewhere

impedance mismatch

occurs when pure resistance is not equal tocharacteristic impedance, and it can be corrected bymeans of "Matching transformer".

Maxima

current/voltage is high, also called loops

Minima

current/voltage is low, also called nodes * At current loop the voltage is minimum (voltage

node) and at current node voltage is max (voltage

loop)

Transmission line mismatch loss

also known as standing wave loss, occurs in the form ofheat dissipation

resonance

condition where in the capacitive and inductivereactance cancels out.

Resonant frequency (Fo)

lowest frequency at w/c resonance occurs. also knownas fundamental frequency

Fo = 1/[2pi(LC)^1/2]

standing wave

also known as a stationary wave, is a wave thatremains in a constant position. This phenomenon can

occur because the medium is moving in the oppositedirection to the wave, or it can arise in a stationarymedium as a result of in terference between two wavestraveling in opposite directions

series resonance

There is no opposition of alternating current at resonantfrequency

Parallel resonance

There is a large opposition to alternating current @ Fo.


22/24

CHAPTER 18 : TRANSFORMERS AND IMPEDANCE MATCHING

Transformers can:

Stepping up or down a voltage Matching impedance Provide DC isolation Balanced to Unbalanced (vice versa)

In its simplest definition, a TRANSFORMER CHANGES one voltage

to another voltage value, either higher or lower (step-up or stepdown); kaya siya tinawag na TRANSFORMER!

How does a transformer do that?

When two wires are near each other, and one of themcarries a fluctuating current, a current will be induced in theother wire. This effect is known as electromagnetic induction(Isipin niyo antenna).

- Mas malapit mas malakas ang induced current- Pero mas lalakas kung the wires are wound into coils

and placed along a common axis

- Pero di pa dyan natatapos, even more coupling , orefficiency of induced-current transfer, is obtained if thetwo coils are wound one atop the other

First Coil = Primary Winding -----------Secondary Coil = Secondary Winding

Note:

As the frequency increases, the needed inductancedecreases. At high-resistive impedances, moreinductance is generally needed than at low-resistiveimpedances.

Turns Ratio:

ratio of the number of turns in the primary to thenumber of turns in the secondary

E = voltage ; T = turns

For a transformer with excellent coupling; the relationship is:

Primary to Secondary turns ratio

Step Down : Ratio is greater than 1 : Larger number overSmaller number

Step Up : Ratio is less than 1 : Smaller number overLarger number

(Siyempre babaliktad yung mga conditions kapag Secondary toPrimary na yung ratio)

Transformer Cores:

Why use cores?

To confine the flux thus increasing the coupling or theefficiency of the induced-current transfer

Air Core Ferro-Magnetic Core

Laminated Iron

Used at 60-Hz utility ac and low audio frequency Sheets of silicon steel glued together in LAYERS Called transformer iron or plain iron Layers are used instead of a single mass of metal to

prevent eddy currents Eddy currents go in circles , heating up the core and

wasting energy; pero pag layered hindi maka-flow ngmaayos yung mga eddy currents in circles kayanapipigilan

Laminated cores exhibit high hysteresis loss above

audio frequencies Therefore not good above a few kilohertz.

Hysteresis loss

core materials become sluggish (bumabagal yungresponse) in accepting fluctuating magnetic field

Ferrite

Frequencies up to FEW megahertz and works well for RF(radio-frequency) transformers

High Permeability and concentrates flux efficiently High permeability REDUCES the number of turns

needed in the coils Higher than few megahertz; shows losses and becomes

ineffective

Permeability

is a measure of how well a material will "conduct" amagnetic field.

Powdered Iron Core

works well at VHF (very high frequency); 100 Mhzpataas.

permeability is less than that of ferrite but at highfrequencies it doesnt matter

At Radio Frequency above a few megahertz; air coresare preferred!


23/24

Transformer Geometry:

Utility Transformer

E-core common core is the E-core so called because of its

shape winding method includes the shell and the core

winding method shell method provides the best coupling however

capacitance occurs (may or may not be tolerated)

and also cannot handle very much voltage nasa middle bar lang yung winding ng primary andsecondary

core winding method ; primary is at the bottome of theE-section and the secondary is placed at the top

capacitance is much lowe r and can handle highervoltages

both are universally employed at 60 Hz

Solenoidal Core

more commonly used as a loopstick antenna inportable radio receiver and in radio direction findingequipment

as a loopstick; primary serves as receiver andsecondary matches impedance

core windings may be on top of each other orseparated (to reduce capacitance)

Toroidal Core

donut-shaped ring of powdered iron or ferrite used for radio frequency transformer windings maybe on top or on separate parts confines the magnetic flux in the core material

(pwedeng itabi sa ibang components)provides more inductance per turn

Pot Core

even more inductance per turn can be obtained

self shielding primary and secondary must be wound on top or next

to each other (no choice) therefore capacitance is rather high generally employed at lower frequencies because you

dont need much inductance at higher frequencies

Autotransformer

when its not necessary to provide DC isolation single- tapped winding

found sometimes on radio-frequency receiver ortransmitter

works well in impedance matching Can be (but not often) used in utility circuits steppingdown by a large factor but only step up a few percent

Power Transformer

At the generating plant:

extremely high voltages are used why ? Because lower current means reduced loss in the

transmission line recall P = IE cant control the wire resistances and the power used

at the loads; the only parameter we can change is thevoltage

as a result massive transformers are used to handle thehigh voltage

Along the line:

step down transformers are used . Why? voltage from plants amount to around kilovolts , (isipin

niyo kung ang outlet niyo sa bahay naglalabas ngganung kataas na voltage baka lalapit palang kayomay tumalon ng kuryente sa inyo), that is why there is aneed to step down the voltage

At individual houses and buildings:

voltage is further stepped down to 234-V electricity inthree phases (separated by 120 degrees ) or 117-Voutlet supplies just one phase (ground yung thirdprong)

Audio-Frequency Transformer

Frequencies are higher and exist as band offrequencies (20 Hz to 20 kHz)

transformers used are still similar but instead ofchanging voltages; they MATCH IMPEDANCES

Isolation Transformer

isolating two circuits by not directly connecting them only allows AC but not DC the amount of capacitive coupling can be greatly

reduced (by separating the wires)

Balanced and Unbalanced load (Balun)

balanced = terminals can be reversed without anyeffect on the circuit (resistor , antenna)

unbalanced =must be connected in a certain way towork properly (usually when one side is connected tothe ground) ex. Coaxial lines

the transformer can allow for the mating of thebalanced and the unbalanced load

the turns ratio might be 1:1 if the impedances arematched ; if the impedances doesnt match the turnsratio should be changed


24/24

Transformer Coupling

used in amplification by offering some advantages(usually in radio-frequency receiver and transmitter)

too many feedback, amplifiers would start to oscillatedegrading the performance BUT transformer minimizethe capacitance preventing oscillation

Impedance Transfer Ratio

To match the impedances in radio-frequency and

audio frequency circuits

For purely resistive impedances:

Z=impedance ; E = voltage ; T = turns

Radio-Frequency Transformer

Coil types

Powdered-iron cores ----->>> quite highfrequencies

Toroidal cores ----->>> most commonbecause self-shielding

Number of turns depends on the frequency , and also on thepermeability of the core

Air-core ----->>> although low permeability also haslow hysteresis loss

One disadvantage is the magnetic flux extends outside the coilMajor advantage of coil type transformer, (especially toroidalcore) is that they can be used over a wide band of frequencies such as from 3.5 MHz to 30 MHz (broadband transformers)

Transmission-Line types

transmission lines are sometimes used as impedancetransformer due to its own characteristic impedance

always made from quarter wave sectio ns or (length

of quarter wave section)

where Lft is the length of the section in feet, v is thevelocity factor expressed as a fraction, and f o is the frequency ofoperation in megahertz. If the length Lm is in meters,

-Let a quarter-wave section of line, with characteristicimpedance Zo , be terminatedin a purely resistive impedance Rout . Then the input impedance isalso a pure resistanceRin , and the following relationship holds:

These relationship will hold at frequency f o , a line 1/4wavelength long ; Neglecting losses will also hold true forodd harmonics at 3 f o , 5 f o , 7 f o , and so on.

the quarter wave matching section should be madebalanced (for loads that are balanced) and

major disadvantage is working only at certainfrequencies

Reactance

unfortunately hinde purely resistive ang mgaimpedance

Reactance makes a perfect match impossible!! Nomatter what the turns ratio or Zo of the transformer, areactance would always exist which can be toleratedat lower radio frequencies (below about 30 MHz) but a

near-perfect match becomes more important athigher frequencies although hinde sakop ng chapter na ito. Recall na

kapag may reactance (X) not equal to zero, to cancelit, add an equal and opposite (-X) which can be doneby adding an inductor or capacitor in series sa load

transmatch

is a device that i s wide band and has adjustableimpedance-matching and reactance cancellingnetworks located between the antenna and thetransmitter (from 1.8 Mhz to microwave).

Complete Gibilisco

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Transcript of Complete Gibilisco