Electrical and Electronic Workbook

8/11/2019 Electrical and Electronic Workbook

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Petersfield High School

Follow Occupational Health and Safety

Hazard: A circumstance that increases the likelihood or probable severity of a loss. For

example, the storing of explosives in a home basement is a hazard that increases the

probability of an explosion. Accident: An unexpected and undesirable event, especially one resulting in damage or

harm:

Emergency: A serious situation or occurrence that happens unexpectedly and demands

immediate action.

Developing safe working habits depend on the right working attitude a feeling that you

want to feel safely.

Failing to follow electrical safety rules and practices can in!ure you or others and destroy

property. "hock and burns can result when the body conducts electricity. #roperty may be

damaged by electrical fires started by overheated wires or sparks. $hese dangers must be

prevented if we are to use electric energy safely and efficiently.

As a future worker, you will become familiar with the occupational %ealth and "afety Act

&'%"A(. )ts basic purpose is to ensure that every worker in the nation has safe and

healthful working conditions.

$he main causes of accident in the workshop include:

Carelessness: *hen any !ob is done often enough, it tends to become boring and boredom

easily leads to careless work. For example, a maintenance electrician may continually

check control e+uipment when it is live and become unconscious of the danger. Dont let

familiarity breed contempt.

Ignorance: Accidents often occur in industry due to the ignorance or inexperience of

workers. -emember that most tasks look easy when done by an expert. Do not attempt a

difficult !ob unless under supervision.

Skylarking: any young people work in industrial premises without a full realization of the

hazards present. "kylarking may be a legitimate way of letting off steam/ in a school

playground, but it can often lead to serious and, sometimes, fatal accidents in a factory or

workshop. "ensible people often do things they would never otherwise do when they are dared.

Electrical and Electronic TechnologyFollow Occupational Health and Safety

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PERSON! PRO"EC"I#E E$%IP&EN"

$he essence of safety is protection. #ersonal protection re+uires e+uipment designed for

individual safety. *hen wearing personal protective e+uipment, make sure that the e+uip0

ment is in good condition, that it fits, and that it is approved for the specific task being per0

formed. "ince electrical e+uipment is used in nearly every environment, make sure that

your personal protective e+uipment is appropriate for the environment, as well as for the

specific electrical application.

Safety 'lasses

"afety glasses are re+uired in all manufacturing facilities and most school laboratories.

"afety glasses should be worn when soldering, cutting wires, handling chemicals and

television picture tubes, and using machines such as drill presses, portable electric drills,

and grinders.

1lass lenses and some plastic lenses do not +ualify as safety glasses since they can shatter

and cause serious eye in!ury. 1oggles should be worn over safety glasses when there is a

danger of fluids, dust, or rust falling or splashing into the eyes.

Clothing

#ersonal grooming from the safety standpoint has little to do with personal grooming

from the aesthetic standpoint. Flowing hair, heavy !ewelry, and loose clothing may look nice,

but that long hair can easily get caught in machinery or obscure your vision. %eavy !ewelry

can get in the way and conducts electricity. 2oose clothing can interfere with movement,

restrict activity, and get caught in machinery.

3lothing can cover the body to protect it from solder burns, battery acid, and general

external contamination. )n some instances, rubber or latex gloves are necessary to protect

the skin, eg. %igh voltage.

&ask and Respirators

-espirators must be worn by engineers, technicians, and scientists working in

contaminated areas.

Footwear


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'ne should always wear rubber bottom hard boots to safeguard from electric shocks,

Head 'ear

%elmets are worn where the danger of falling ob!ects exists.

Points of (anger for the Electrician: $hese are as follows:

)* Burns. 4lectrical burns are generally more dangerous &and more painful( than

normal burns, as they are usually caused by an arc containing molten metal.

+* Falls. A very large percentage of industrial accidents are caused by falls, eitherfrom a height or by workers tripping over e+uipment left lying about.

,* Ladders. #oints to note:

&a( 2adders should always be placed at a reasonable angle to the vertical.

(b) 2adders should be anchored on a non0slip surface or effectively wedged.

(c) Aluminium ladders should be used with great caution, particularly near bare

conductors.(d) Do not attempt to lift heavy, or unwieldy, e+uipment &for example, conduit lengths(

up or down a ladder unaided.

(e) Do not attempt acrobatic feats 0 you may endanger your life and the lives of othersand undermine your right to compensation.

-* Strains. "trains occur through attempts to lift over0heavy weights or by lifting weightsincorrectly. $o lift heavy ob!ects from ground level: place the feet apart, get a good grip

with the fingers, keep the back straight, and lift by straightening the knees

5. Electric shock. $his is one of the main hazards in our craft. )t is not always possible

to work on dead conductors but certain precautions may be taken:

(a) 5ever assume that an installation is dead: check thoroughly before openinge+uipment, and do not check by touching conductors with fingertips.

(b) 3heck circuit thoroughly before replacing a re0loaded fuse in a live circuit. and, if

still in doubt, replace with gloves6 always keep your face clear.

(c) )f working on an installation to which other people have access &for example, acrane(, remove fuses and keep them beside you.

.* Moving machinery. 1reat care should be taken when working on moving

machinery6 oil rags &store in appropriate metal container( and ties &should not be worn(should be kept well clear. Do not remove guards and, if it becomes necessary to remove

a guard, do so when the machinery is stationary. -eplace all guards before leaving a

machine.

1oggles should always be worn when operating a grinder and particular care should be taken when drilling and grinding soft metals &for example, brass and copper(.

First id

5'$4. First aid is only meant to be a temporary measure until skilled assistance can be


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obtained.

First/id 0o1* 4very factory and workshop is legally bound to possess a first0aid box.

)ndustrial first0aid kits should contain: sterilized dressings, cotton wool, adhesive plaster,

roller bandages &78 mm and 89mm(, sal volatile, and eye drops.

"reat2ent for Cuts. Do not wash the wound, although the skin round it may be

cleansed with soap and water. Apply a sterilized dressing, or an adhesive wound

dressing, as +uickly as possible.

"reat2ent for 0urns* )f serious, send for a doctor or ambulance. 3over the wound

with a sterilized dressing, do not apply adhesive dressing or ointments.

Chemical burns. Flush with cold water immediately and apply sterilized dressing. se

antidote if available &solution of bicarbonate of soda for acids and dilute vinegar for

alkalines or buffered phosphate solution for both types of burns(. Alkaline burns aremore serious than acid burns and should receive medical attention as +uickly as

possible. "reat2ent for Electric Shock* An electric shock is caused by the passage of

current through the body &generally hand to hand or hand to feet( causing a paralysis of

the muscles, particularly the heart muscles. 3urrents as low as 9.979 A have been known

to be fatal. $he severity of the shock will depend on: &a( voltage between live metal

and earth, (b) moisture content of skin, (c) proximity of body to effective earth, and (d)

length of time of contact.

"#44D is 4""45$)A2 in treatment for electric shock. A few minutes delay may make all the

difference between recovery and death.

;. "witch off current before attempting to remove the casualty or, if this is not possible,

remove him with an insulated material &for example, !acket, dry wood or dry newspaper(. Do

not touch or attempt to grasp casualtys skin.

7. -emove any obstructions to breathing &for example, tight collar or false teeth(.

<. 3ommence artificial respiration, using the mouth0to0mouth method. &$his should

be practiced by everyone working with electricity as efficiency can only come with

practice.(

&outh/to/2outh rtificial Respiration

;. #osition casualty on floor with head tilted backwards &Fig below(.

7. $ake a very deep breath.


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<. #ress his nose between your fingers.

=. #lace your mouth against his mouth and form an air0tight seal.

8. >low into his lungs until his chest expands.?. -emove your mouth and watch for the contraction of his chest.

@. -epeat the above until his breathing returns to normal. 5'$4. outh0to0nose

artificial respiration should be carried out if the casualtys mouth is blocked &e.g. due toin!ury(.

ccident 0ook

All employers are obliged by law to enter all accidents in the accident book. $his book


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is used to register:

(a) Date of accident.

(b) 5ame of patient.

(c) 5ature of in!ury.

(d) 3ause of in!ury.

(e) $reatment.

)t is essential that any in!uries received during working hours be reported by the employee

or claims for industrial benefits may be affected.

C"E'ORIES OF FIRE

Class : those involving ordinary solid combustible materials such as paper, cloth,

plastics, wood, etc.

Class 0: those involving flammable li+uids such as oil, fat, grease, adhesives, paint,

varnish, petrol, etc.Class C: those involving flammable gas such as 2#1 &li+uefied petroleum gas(, butane,

propane, methane, acetylene, etc.

Class (: those involving metals, molten metals, metal powders, etc.

Electrical: those involving fixed e+uipment such as switchgear, motors, computers,

and portable e+uipment such as hand0held appliances, toasters, hairdriers, etc.

$he following action should be taken in the event of a fire:

a( -aise the alarm.

b( "witch off the supply &if an electrical fire(.

c( 3lose doors and windows to prevent spread of fire.

d( Fight the fire if trained to do so &see = below(.e( "top fighting the fire if: &i( it is out of control6 &ii( you are threatened by smoke6 or &iii(

your escape route is blocked.

ypes of fire extinguishers:

• 3ater type: for 3lass A fires only.

• &ulti/purpose dry powder: for 3lass A, > and electrical fires, although it does not

penetrate the spaces in e+uipment.

• Standard dry powder: for 3lass > fires.

• Halon: for small0burning surface 3lass A fires, 3lass > fires and electrical fires.

• &ulti/purpose a4ueous fil2/for2ing foa2: for 3lass A and 3lass > fires.

• Foa2: 3lass > fires.• Car5on dio1ide &3'7(: 3lass > fires and live electrical e+uipment.

• Fire 5lanket: for 3lass A and > fires.

5ote For 3lass 3 fires, if there is no risk of explosion, use multi0purpose dry powder, halon

or 3'7 extinguisher. For 3lass D fires, special training is needed.

5ote >oth halon and 3'7 type extinguishers chemically inhibit combustion, but harmful

fumes can be given off so they should not be used in confined spaces.





Fire !lan"et

Figure 1#4 Types of fire e$tinguisher


%ry powder

&lac" &lue

Foa'(ater

)ed *rea'

%ry powder

&lac" &lue

Foa'(ater

)ed *rea'

+




Fire !lan"et

Figure 1 Types of fire e$tinguisher

"esting 'as leak

)n the event that there is gas leak spray soapy water on the gas line and wait to see

where the bubbles come from to find the location of the leak.

%sing the grinder

• "tand to the side of the grinder when starting the grinder

• Always wear full0face protection, ear protection, leather gloves and a leather

apron.

• As with all other machines ensure that the guard is in place before use.

• Do not grind on the side of the wheel because it may cause the wheel to shatter.

• ake sure you understand and observe all legislative and personal safety

procedures when carrying out the following tasks.• )n the event that chips are caught in any machine, stop it then use a wire brush to

remove the obstruction.

Hydraulics is a topic of science and engineering dealing with the mechanical properties

of li+uids. %ydraulics is part of the more general discipline of fluid power . Fluid

mechanics provides the theoretical foundation for hydraulics, which focuses on the

engineering uses of fluid properties.

Hydraulic 2achinery are machines and tools which use fluid power to do work. %eavy

e+uipment is a common example.


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http://en.wikipedia.org/wiki/Engineering



http://en.wikipedia.org/wiki/Fluid_power

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http://en.wikipedia.org/wiki/Engineering_vehicle













)n this type of machine, high pressure hydraulic fluid is transmitted throughout the

machine to various hydraulic motors and hydraulic cylinders. $he fluid is controlled

directly or automatically by control valves and distributed through hoses and tubes.

Pneu2atics, a subsection of an area called fluid power , is the use of pressurized gas to

effect mechanical motion.

E1a2ples of pneu2atic syste2s:

• #neumatic tools:

o #neumatic drill &!ackhammer( used by road workers

o #neumatic nailgun

• #neumatic switches

• #neumatic actuator

• Air compressors • acuum pump

O1y/fuel refers to technology that burns oxygen with gaseous fuel. As compared to air ,

which contains 79.B8C oxygen, higher temperatures can be reached using pure oxygen.

Approximately the same total energy is produced when burning a fuel with oxygen as

compared to with air6 the difference is the lack of temperature diluting inert gases. $he

most common fuel burned in a torch with oxygen is acetylene6 even though it presents

special handling problems, it has the greatest heat output


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http://en.wikipedia.org/wiki/Hydraulic_fluid

http://en.wikipedia.org/wiki/Control_valves

http://en.wikipedia.org/wiki/Hydraulic_machinery#Hose.2C_tubes_and_pipes






http://en.wikipedia.org/wiki/Pressurized_gas



http://en.wikipedia.org/wiki/Pneumatic_tools

http://en.wikipedia.org/wiki/Pneumatic_drill

http://en.wikipedia.org/wiki/Nailgun


http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Pneumatic_actuator

http://en.wikipedia.org/wiki/Gas_compressor


http://en.wikipedia.org/wiki/Vacuum_pump

http://en.wikipedia.org/wiki/Combustion



http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/Fuel

http://en.wikipedia.org/wiki/Air

http://en.wikipedia.org/wiki/Acetylene

http://en.wikipedia.org/wiki/Hydraulic_fluid

http://en.wikipedia.org/wiki/Control_valves





http://en.wikipedia.org/wiki/Pneumatic_tools

http://en.wikipedia.org/wiki/Pneumatic_drill


http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Pneumatic_actuator


http://en.wikipedia.org/wiki/Vacuum_pump


http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/Fuel

http://en.wikipedia.org/wiki/Air

http://en.wikipedia.org/wiki/Acetylene




Electron TheoryMatter is anything that occupies space and has 'ass# (ire. ru!!er. and glass are e$a'ples of'atter# /atter is 'ade up of tiny particles called molecules. /olecules are 'ade up of e0ens'aller particles called ato's# n ato' is 'ade of tiny particles called electrons. protons. andneutrons# Electrons are negati0ely charged particles that re0ol0e around the nucleus of an ato''uch li"e planets around the sun# Protons, positi0ely charged particles. and neutrons are heldtightly together in the nucleus, or center. of the ato'#

These particles are i'portant !ecause they deter'ine the charge of an ato'#The electrons are held tightly in place !y the attracti0e force of the electrons#Since electrons are attracted to protons. it 'eans they !oth ha0e tiny a'ounts of energy#

There is a force F !etween charges# i"e charges repel unli"e charges attract#

The force is directly proportional to charge# The force is in0ersely proportional to s6uare of distance#

Electrons ha0e negati0e 7 charges# Protons ha0e positi0e 8 charges# 9eutrons ha0eno electrical charge# Thus. they are neutral#

The a'ount of the negati0e charge of each electron is e6ual to the a'ount of the positi0e

charge of each proton# :f an ato' loses an electron. it will attract another electron towards it !ecause unli"e

charges attract electrons fro' ato' to ato' is going on continuously and is affected !yte'perature#

(hen an electric pressure a 0oltage is applied across a 'aterial the electrons 'o0e inone direction only

*on0entional *urrent Flow 0s# Electron Flow


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*on0entional Flow< Flow of positi0e charges fro' positi0e to negati0e Electron Flow< Flow of electrons fro' negati0e to positi0e

Electric *urrent This uni7directional 'o0e'ent. or flow. of electrons is called a flow of current. The unit of current is the ampere a!!re0iation and the sy'!ol is :# The current denotes the rate of flow of charges#

Electric *harge The unit of electric 6uantity is the coulomb sy'!ol Q). One coulo'! is the 6uantity of

electricity con0eyed in one second !y a current of one a'pere #3 $ 1; 1, electrons in

one second# 1 coulo'! * = 1 a'pere : flowing for 1 second (t) For'ula< > = : $ t

Energy of the electrons The electrons recei0e energy fro' the 0oltage source as it cause electrons to flow in the

circuit# This energy can !e found using the for'ula< Energy = *harge $ ?oltage E = > $ ?

Electric Pressure ?oltage is the pressure that cause electrons to 'o0e through a circuit. 'uch li"e pu'p to

water#

The unit of electric pressure is the volt ? One "ilo0olt "? = 1;;;? 9OTE< Electric pressure. li"e any other pressure 'easure'ent. is 'easured !etween

two points#

Electrical Resistance The flow of electric current. li"e any other flow or 'o0e'ent. is su!@ect to friction# The friction. or opposition. which a 'aterial presents to a flow of current is called

resistance. unit of electrical resistance is the ohm and the sy'!ol is A Bree" letter o'ega# *onductance is the opposite of resistance# The less the resistance the higher the

conductance# The sy'!ol for conductance is B. and the unit is Sie'ens S# B = 1C) or B = 1C?C: or B = :C?

Relationship between Voltage, Current, and Resistance :f the resistance (R) to a flow of current : is increased. while the 0oltage (V) re'ains

constant. the current will decrease# :t is assu'ed that the te'perature of the resistance re'ains constant# n increase in R decreases :# : is in0ersely proportional to )# (I ∞ 1/R)

Oh's aw :f the resistance (R) re'ains constant and the 0oltage V) increases. the current : will

increase#


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n increase in V increases I. I is directly proportional to V (I ∞ V)

:. ?. and ) are related in a general for' "nown as Oh'Ds aw# hm!s "aw states that the current (I) flowin# in a circuit is $irectl% proportional to the

volta#e (V) but inversel% proportional to the resistance (R) when temperature remainsconstant.

Fro' Oh's law we deri0e<

: = ?C) This 'eans that if the 0oltage to a circuit is increased fro' 3? to ? when the resistance

re'ains constant at 3A. then the current will increase fro' 1 to 2#

Braph showing Oh's law

cti0ity1# relay operates at 4,? and draws 3;# (hat is its resistance2# (hat current is carried !y a 2+A line cord resistor if the 0oltage drop across it is 4;#5?3# 5A heating ele'ent draws 15 fro' the power source# Find the 0oltage drop across

the heating ele'ent

/ESG):9B FG9%/E9T >G9T:T:ES/easuring resistance

The oh''eter is used to 'easure s'aller 0alues of resistance it is also used for circuittracing#Gsing the oh' 'eter

Oh''eters are connected in parallel with the ter'inals of the de0ice or circuit to !etested# The de0ice or circuit 'ust !e disconnected fro' power and fro' any portion ofthe circuit that is not to !e tested# False readings will result if other co'ponents areconnected to the test circuit# %o not let the fingers of !oth hands touch the tips of the testleads while 'easuring resistance#

:f you do. the oh'7'eter will 'easure the co'!ined resistance of your !ody and the circuit !eingtested# &e 0ery careful of this when 'easuring high 0alues of resistance. as your !ody resistanceis high and will affect the total resistance of another high resistance# false reading can causeyou to 'a"e a poor decision when trou!leshooting a circuit#


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Voltmeter 0olt'eter is a testing de0ice used to 'easure 0oltage# The 'eter test leads or wire

connections are attached to the tested circuit in parallel with the de0ice that is e$pectedto ha0e a 0oltage drop#

Gsing the ?olt'eter

?olt'eters are always connected in parallel to the de0ice or circuit across which the 0oltage is to!e 'easured# dc 0olt'eter is a polariIed instru'ent# This 'eans that care 'ust !e ta"en to

connect the test leads to the correct polarity. or 8 to 8 and 7 to 7 # :f this is not done. a digital 'eter will indicate a negati0e 0oltage. which 'ight confuse the data#

(hen testing for %* 0oltage and a negati0e reading appears it is due to the polarity ofthe test leads to the circuit or co'ponent !een tested#

n ac 0olt'eter can !e connected across two points under test regardless of polarity#

Using Ammeters ''eters are connected in series with the conductors and the load !eing tested Fig# 227

-# They can !e per'anently da'aged if connected into circuits with too 'uch current# dc a''eter should !e connected into a circuit with the correct polarity# digital a''eterwhich has !een connected incorrectly will indicate a re0erse polarity on the display# :f a'o0ing coil 'eter is connected in re0erse. the pointer will 'o0e in the wrong direction

and 'ay !e da'aged# n ac a''eter can !e connected into a circuit without regard forpolarity#

)eading the nalogue /eter


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(hen ta"ing a reading on so'eparts of electronics the reading fluctuates so 'uch a digital 'eter would !e rendereduseless !ecause the display would ne0er settle down#

%isad0antages )esolution of analog 'ulti'eters is li'ited !y the width of the scale pointer . paralla$.

0i!ration of the pointer. the accuracy of printing of scales. Iero cali!ration. nu'!er ofranges. and errors due to non7horiIontal use of the 'echanical display#

ccuracy of readings o!tained is also often co'pro'ised !y 'iscounting di0ision'ar"ings. errors in 'ental arith'etic. paralla$ o!ser0ation errors. and less than perfecteyesight#

cti0ity

The figure a!o0e indicates three resistance readings ta"en !y an oh''eter#

write the letters J . K and L # 9e$t to E*H letter. write the 0alue of reading indicated#


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P)TS OF *:)*G:T n electric circuit is a co'!ination of parts connected to for' a co'plete path through

which electrons can 'o0e# The purpose of a circuit is to 'a"e use of the energy of 'o0ing electrons#

Therefore. a circuit is also a syste' of parts. or co'ponents. !y which electric energycan !e changed into other for's of energy. such as heat. light. or 'agnetis'#

*o'ponents of a circuit The !asic co'plete circuit has fi0e parts< 1 the ener#% source 2 the con$uctors 3 the load 4 the control $evice 5 the protection

The Energy Source The energy source in a circuit produces the force that causes electrons to 'o0e# :t is li"e

a pu'p that forces water through a pipe# :n electricity. this force is called 0oltage. or electromotive force (&). E$a'ples< *he'ical cell !attery and a generator

*onductors The conductors in a circuit pro0ide an easy path through which electrons can 'o0e

through the circuit# *opper is the 'ost co''only used conductor 'aterial# *opper wire 'ay !e !are or

co0ered with so'e "ind of insulating 'aterial# The insulation pro0ides a 'ethod to pre0ent the conductors wires fro' touching each

other or so'e other conducting surface# Thus. the insulation pre0ents a short circuit#


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*onductors for e0eryday use 'ust !e (a) of low electrical resistance. (b) 'echanically strong and fle$i!le. and (c) relati0ely cheap# For e$a'ple. sil0er is a !etter conductor than copper !ut it is too e$pensi0e for practical

purposes# Other e$a'ples of conductors are alu'inu'. tin. lead. gold and iron#

:n an auto'o!ile the entire car fra'e ser0es as a conductor# :t co'pletes a nu'!er ofcircuits that connect the 0oltage source the car !attery to 0arious electrical andelectronic de0ices#

:nsulator true insulator is a 'aterial that does not respond to an electric field and co'pletely

resists the flow of electric charge# :n insulating 'aterials 0alence electrons are tightly !onded to their ato's# Their function is to support or separate electrical conductors without allowing current

through the'sel0es#*a!le

length of insulated single conductor solid or stranded. or of two or 'ore suchconductors each pro0ided with its own insulation. which are laid up together#

ca!le consists of two !asic parts< a the conductor and ! the insulator

oad The load is the part of a circuit that changes the energy of 'o0ing electrons into so'e

other useful for' of energy# light !ul! is a 0ery co''on circuit load# s electrons 'o0e through the fila'ent of the

la'p. the energy of the electrons in 'otion is changed into heat energy and light energy

*ontrol %e0ice

The 'echanical wall switch is an e$a'ple of a si'ple circuit control de0ice# :t opens andcloses a circuit#

(hen the switch is Mon.M it acts as a conductor to "eep electrons 'o0ing through thecircuit# The circuit is said to !e closed# :n this condition. the circuit has a closed loop#(hen the switch is Moff.M the circuit path is interrupted# Electrons can no longer 'o0e


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through the circuit# The circuit is said to !e open that is. it has an open loop#


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PO(E) 9% E9E)BK Energy sy'!ol E or ( is the a!ility to do wor" and is 'easured in Noules Sy'!ol N# Power is the rate of doing wor" The rate at which an electric circuit does the wor" of con0erting the energy of 'o0ing

electrons into so'e other for' of energy# The unit of power is the watt (# The power of a de0ice is 1 (att 1( if it changes

energy at the rate of 1 Noule per second# Hence Power P = Energy E Cti'e t

/a$i'u' power rating E0ery electronic co'ponent has a 'a$i'u' power rating which should not !e e$ceeded#

For e$a'ple a 1( resistor can safely change 1 N of electrical energy per second intoheat without da'age#

Electrical e6uip'ent is rated in ter's of the a'ount of power. or watts. it uses# E$a'ple<a light !ul! rated at ; watt. 1;; watt. 1"( etc#

arger Gnit of /easure'ent of Energy )ecall< (or" and energy are essentially the sa'e with identical units and E = P $ t The Noule is a 0ery s'all unit of 'easure'ent. for larger a'ounts of electrical energy the

"(h is used# s E = P $ t

"(h = "( $ h

E$a'ple How 'uch electrical energy in "ilowatt hours "(h is used !y a 15;( light !ul! if it is

on for 12 hours E = P $ t E = 15;( $ 12h E = 1,;; (att hours (h or 1#,"(h

:f the cost of electricity is Q5#1;C "(h then the total cost for the 1#,"(h of energy would!e<

*ost = energy $ rate *ost = 1#,"(h $ Q5#1; *ost = Q-#1,

E$ercise For the 6uestion that follow. assu'e that the cost of energy is Q,#5; centsC"(h How 'uch will it cost to run a 5( electric cloc" for 3; days How 'uch will it cost to light a 1;;( !ul! for 3; days

cti0ityThe a0erage wattage ratings of se0eral household electric appliances are gi0en in the ta!le!elow# t the cost of Q-#5 per "(h. co'pute the cost of operating each of these appliances for 3hour# dd this infor'ation to the ta!le#

ppliance 6erage 3attage Rating Cost of Operation for )

hour 7 89*. per k3h

icrowave 'ven ;, 899

-efrigeratorEfreezer,

frostless

?79


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$elevision, 3olor, "olid

"tate

;89

*ashing machine, 899

/eter )eading (att7hour 'eters 'easure the electric energy in "ilowatt7hours supplied !y electric power

co'panies to users# Such a 'eter is usually 'ounted on the side of a !uilding# :t is'onitored. or read. at certain ti'es# This reading is used to calculate the electric !ill for aperiod of ti'e. usually one 'onth#

)eading a )esidential /eter

There are se0eral different "inds of 'eters used to 'easure electricity. including the four7

dial. fi0e7dial and digital 'eters# /ost ustin Energy ho'es utiliIe the fi0e7dial electric'eter#

The first. third and fifth hands on the 'eter 'o0e cloc"wise around the dial# The secondand fourth hands 'o0e counter7cloc"wise#

Start with the right dial# )ecord the nu'!er indicated on the face of each dial#

*ontinue until you ha0e read all fi0e dials#

/eter )eading Tips lways record the lowest nu'!er if the hand points !etween two nu'!ers# So'eti'es. a hand will see' to !e pointing e$actly at a nu'!er# To find out if the hand

has really reached that nu'!er. loo" at the dial to the right# :f the hand on that dial haspassed Iero. then you should record the nu'!er otherwise. record the lower nu'!er#

*alculating energy !ills The electric !ill is calculated using two separate readings i#e# to get the energy usage for

a one 'onth period. there is a first reading then one 'onth ti'e a second reading ista"en then the difference !etween these readings would !e the energy usage for the'onth#

Energy usage = Present reading 7 pre0ious reading

*ost = energy used $ rate

cti0ity The figure !elow shows the dials of a four dial watt7hour 'eter for a NPS custo'er#

*alculate how 'uch it would cost the custo'er for the one 'onth period if he pre0iousreading was 1141 and the rate is Q-#25CR(H#


1-




Other For'ula for Power Since : = >Ct then > = : $ t e6uation 1 The energy of the electrons is found using the for'ula< E = > $ ? e6uation 2 )eplacing > with : $ t in e6uation 2 Then E = : $ ? $ t e6uation 4 Since P = ECt and E = : $ ? $ t Then P = : $ ? $ t

t(e recei0e P = ? $ :

Since ? = : $ ) and P = ? $ : )eplacing ? with : $ ) P = : $ ) $ : P = :2 $ ) )eplacing : with ?C) P = ?C) $ ? P = ?2C)

E$a'ple clothes dryer draws 15 fro' a 22;? line# *alculate the a'ount of power used# : = 15 ? = 22;? P = P = ? $ : = 22;? $ 15

= 33;;(

E$a'ple 2+A resistor has ;#;2 of current flowing through it# *alculate the power dissipation# ) = 2+A : = ;#;2 P = P = : $ : $ ) = ;#;2 $ ;#;2 $ 2+A = ;#;1;,(

(or"sheet


2;




)esistance resistor is a electronic de0ice designed to li'it the current that flows in a circuit# Sy'!ol Types of resistors< *ar!on co'position resistor /etal o$ide or 'etal glaIe resistor (ire7wound resistor ight %ependent )esistor %) Ther'al resistor ther'ister

*ar!on resistor These resistors generally ha0e resistance 0alues fro' ;#1A to 22/A# :ts structure consists of a s'all cylinder of car!on which is 'i$ed with a non7conductor#

connecting wire is fi$ed into each end. and the resistor is gi0en a coat of paint to protect itfro' 'oisture which 'ight alter the resistance#

/ade in range of stoc" fro' 1C, ( to 3(

/etal BlaIe oo"s rather li"e the car!on resistor fro' the outside. !ut the internal structure is different *an !e 'ade to closer tolerances than car!on resistors. and *hange their resistance less with changes in te'perature /ade in range of stoc" fro' 1C, ( to 3(

(ire7wound )esistor Gsed in higher power applications The resistance ele'ent of a wire7wound resistor is usually nic"el7chro'iu' wire# This

wire is wound around a cera'ic core# The whole asse'!ly is usually coated with cera'ic

'aterial or a special ena'el High resistance 0alues use wire of low conducti0ity. re6uiring 'any turns of fine gauge

wire as well# Ha0e resistance 0alues fro' 1A to 1;;"A# Power rating range fro' 1 to 5;( in stoc" siIes# There is no li'it in practice


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Rinds of )esistors )esistors 0alue can either !e fi$ed or 0aria!le# fi$ed resistor has a single 0alue of resistance which re'ains the sa'e under nor'al

conditions#?aria!le )esistors< ha0e an ad@usta!le a'ount of resistance in a circuit# The 'ost co''on0aria!le resistors are called the potentio'eter and the rheostat#

Potentio'eter Benerally ha0e car!on co'position resistance ele'ents and are co''only used to 0ary

the 0alue of 0oltage applied to a circuit#

Potentio'eters are co''only used as control de0ices in a'plifiers. radios. tele0isionsets and different "inds of 'eters# Typical uses include 0olu'e. !alance. !rightness andIeroing ad@ust'ents#

)heostat The rheostat is generally 'ade of resistance wire# They are co''only used to control

higher currents. such as those in 'otor and la'p circuits#

potentio'eter can !e connected as a rheostat

Precision resistors So'e wire7wound and fil' resistors ha0e actual 0alues that are nearly e6ual to their

rated 0alues# These are called precision resistors# They are use in special circuits such as in test instru'ents and critical co''unication


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$he center terminal is connected to the wiper




de0ices# Precision resistors usually ha0e a tolerance !etween 1 and 5#

ight %ependent )esistor %)%)s or ight %ependent )esistors are 0ery useful especially in lightCdar" sensor circuits#9or'ally the resistance of an %) is 0ery high. so'eti'es as high as 1;;; ;;; oh's. !ut whenthey are illu'inated with light resistance drops dra'atically#

Ther'istor

Ther'istors also called ther'al resistors re se'iconductor de0ices whose use as transducers is due to the fact that theirresistance changes when their te'perature increases#

its sy'!ol is Ther'istors are used for the 'easure'ent and control of te'perature. !eing heated

either e$ternally or internally !y the current they carry#Gsed as a 'eans of sensing te'perature change# *o''only found e'!edded in 'otor windingsto detect o0erheating#

)esistor *olour *ode *ar!on resistors used in electronic circuits are too s'all physically to ha0e their

resistance 0alue printed on the !ody of the resistor# :nstead. the resistance can !e indicated with the use of colored !ands or stripes# The

color stripes represents nu'erical 0alues#


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http://en.wikipedia.org/wiki/File:Photoresistor.gif




ColorColor ValueValue ColorColor ValueValue

BlackBlack 00 GreenGreen 55

BrownBrown 11 BlueBlue 66

RedRed 22 VioletViolet 77

OrangeOrange 33 GreyGrey 88

Yellow Yellow 44 !ite!ite ""

E$a'ple


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)esistor ?alue = ,2; 1; Tolerance 1; $ ,2; = ,2 Gpper li'it = ,2; 8 ,2 = -;2 ower li'it = ,2; U ,2 = +32 Tolerance range = +32 to -;2

)esistors in Series *ircuit

series circuit is a circuit in which the current has only one path# :n a series circuit. all of the current passes through each of the co'ponents in the circuit#

Total )esistance

)T = )1 8 )2 8 )3 # # # where )T is the total resistance in the circuit. and )1 through )3 . . . are the resistance

ratings of the indi0idual resistors in the circuit# The 0oltage across each resistor is found !y using oh's law ?1 = :T $ )1 ?2 = :T $ )2 V ?T = ?1 8 ?2 8 ?3 Rirchoffs ?oltage law R?

*alculate )T. :T. ?)1. ?)2. ?)3

)T = )1 8 )2 8 )3

= 4A 8 3A 8 5A = 12A


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Solution :T = ?TC)T

= 12?C 12A = 1 ?)1 = :T $ )1 ?)2 = :T $ )2 ?)3 = :T $ )3

= 1 $ 4A = 1 $ 3A = 1 $ 5A = 4? = 3? = 5?

E$ercise

*alculate< )T. :T. ?1. ?2. ?3. PT. P1. P2 and P3

Electrical and Electronic Workbook

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Transcript of Electrical and Electronic Workbook