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All Rights Reserved ©2012 Ng Chee Kin
Written By
Ng Chee KinB.Sc.(Hons.), MBA
[email protected]@blogspot.com.au
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EXPRESS EXPRESS
EXpresS �
�
CHAPTER 1
Respiration
1.1 Human Breathing Mechanism
1. The human respiratory system:
2. The air flow during inhalation:
Nose Trachea Bronchus Bronchiole
Alveolus
3. The air flow during exhalation:Alveolus Bronchiole BronchusTrachea Nose
1.2 Transport of Oxygen in the Human Body
1. The oxygen dissolves in the moist lining of thealveolus and then it diffuses into the blood
capillaries.
2. In the blood capillaries, oxygen will combinewith haemoglobin in the red blood cells to form
oxyhaemoglobin.
Lung
Bronchioles
Trachea
Bronchus
( plural : bronchi)
Bronchiole
Alveolus
( plural : alveoli)
Blood capillaries
around the alveoli
1.3 The Importance of a Healthy Respiratory
System
1. Chemical substances which are harmful to the
respiratory system are:(a) nicotine, tar and carbon monoxide from
cigarette smoke
(b) sulphur dioxide, nitrogen oxide, carbon
monoxide, asbestos dust, coal dust andhydrocarbons from vehicles and factories.
2. Tar and asbestos dust are carcinogenic, whichmeans they can cause lung cancer if inhaled
excessively.
3. Bacteria, viruses and other microorganismsproduce toxins which cause illnesses.
4. We need to improve the quality of air in orderto preserve healthy respiratory system.
CHAPTER 2
Blood Circulation and Transport
2.1 Transport System in Humans
1. The human heart:
Oxygen
Lungs
Heart
Otherbodycells
Movement of oxygenMovement of oxygenated bloodMovement of deoxygenated blood
HaemoglobinOxyhaemoglobin
Key:
Oxygenated blood returnsto the heart
Oxygen enters blood inthe lungs
Deoxygenated bloodpumped out of the heart
Oxygenated bloodpumped out of theheart
Deoxygenated bloodreturns to the heart
3. When oxyhaemoglobin reaches the body cells, it
breaks down and releases oxygen.
4. The oxygen is then absorbed by the body cells
for cellular respiration.
Septum
Vena cava
Semilunarvalves
Rightatrium
Tricuspidvalve
Rightventricle
Aorta
Pulmonary artery
Left atrium
Bicuspidvalve
Leftventricle
Pulmonaryvein
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Deoxygenated blood Oxygenated blood
AortaPulmonary artery
Vena cava
Right atrium
Vena cava
Tricuspidvalve
Rightventricle
Cardiac muscle
Pulmonaryvein
Semilunarvalves
Left atrium
Bicuspidvalve
Septum
Left ventricle
2. Functions of the heart:(a) Pumps blood to all parts of the body.
(b) Transports nutrients and oxygen to the bodycells.
(c) Transports carbon dioxide and waste
materials from the body cells. 3. Types of blood vessels:
Characteristic Artery Vein Capillary
Structure
Size of lumen Small Large Very small
Thickness of wall Thick, muscular, elastic Thin, less elastic,
muscular
Only one cell thick and
not muscular
Speed of blood flow Rapid Slow Very slow
Blood pressure Very high pressure Low pressure Very low pressure
Presence of valves No except at aorta andpulmonary artery
Yes No
5. Double circulatory system:
(a) Deoxygenated blood is pumped from theheart to the lungs and oxygenated blood
flows back again to the heart.
(b) Oxygenated blood is pumped from the heatto the rest of the body and deoxygenated
blood flows back again to the heart.
6. Human blood transports many substances in ourbody.
Substance
transportedFrom To
Oxygen (in
the form ofoxyhaemoglobin)
Lungs All body
cells
Carbon dioxide All body cells Lungs
Digested food
(glucose, aminoacids)
Small
intestine
Liver and
all bodycells
Waste materials(such as urea)
Liver andcells
Kidneys
Hormones Endocrine
glands
Target
organs
2.2 Human Blood
1. Human blood consists of:
(a) 55% plasma
(b) 45% blood cells and platelets 2. Types of blood cells:
Type Function
Red blood cells Carries oxygen from the
lungs to the body cells
White bloodcells
Defends the body againstdiseases
Platelets Helps in blood clotting
3. Functions of blood:
(a) Transports gases and dissolved substances
(b) Protects the body against diseases(c) Maintains the body temperature at 37oC
Smooth
muscle
Endothelium
Lumen
Connective
tissue
Connective
tissue
Smooth
muscle
Endothelium
Lumen EndotheliumLumen
4. Path of blood flow in the circulator system:
Deoxygenated
blood
Right
atrium
Right
ventricle Internal organs(for example,
liver, gut)
Rest of the body (forexample, head, arms,
legs)
Left
ventricle
Left
atrium
Oxygenated
blood
Lung
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4. Compatibility of blood groups:
Recipient’s blood
Donor’s groupblood group
A B AB O
A
B
AB
O
5. Universal donor is a person with blood group O.
6. Universal recipient is a person with blood group
AB.
2.3 Transport System in Plants
1. The transport system in plants is called the
vascular system. 2. There are two main vascular tissues:
(a) Xylem- transports water and mineral salts
from the roots to the leaves(b) Phloem- transports glucose from the leaves
to all parts of the plants
3. Xylem and phloem are found in the vascularbundle.
4. Transpiration is the process by which plant loses
water, in the form of water vapour. 5. Transpiration happens through the stomata
(singular: stoma), tiny pores on the leaves of
the plant. 6. Factors that affect the rate of transpiration:
(a) Light – the brighter the light, the greater
the rate of transpiration.(b) Temperature – the higher the temperature,
the greater the rate of transpiration.(c) Humidity – the lower the humidity, the
greater the rate of transpiration.
(d) Wind – the faster the movement of air, thegreater the rate of transpiration.
7. Transpiration helps plants to absorb and transport
water and minerals.
CHAPTER 3
Excretion 3.1 Human Excretion
1. Excretion is a process of eliminating waste
products from the body.
2. The organs responsible for removing wasteproducts are called the excretory organs.
3. The waste products removed from the body are
called the excretory products.
Excretory organ Excretory products
Skin Water, mineral salts, urea
Lungs Water, carbon dioxide
Kidneys Water, mineral salts, urea
4. Excretion helps to maintain the balance of watercontent, chemical composition and pH in the
body system.
3.2 The Urinary System in Humans
Vena cava
Renal
vein
Right
kidney
Urethra
Aorta
Adrenal
gland
Renal
artery
Left
kidney
Ureters
Urinary
bladder
Xylem
Phloem
Cross section of leaf
Cross section of stem
Cross section of root
Epidermis
PhloemXylem
pith
vascularbundle
Root hairCortex
EndodermisXylem
Phloem
Epidermis
Cortex
Medulla
Cortex
Medulla
Pyramid
Ureter
Pelvis
Renal vein
Renal artery
1. The human urinary system consists of: kidney,
ureter, bladder and urethra. 2. Functions of kidneys:
(a) To filter blood.
(b) To remove urea, excess mineral salts andwater to form urine.
(c) To control the balance of water and chemical
in the body.
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3. Kidney failure happens when the kidneys of
a person unable to perform their functionsproperly.
4. Kidney failure can be treated through dialysis
or kidney transplant. 5. Dialysis is a method used to filter and remove
waste products from the blood of a patient.
3.3 Excretion in Plants
1. Plants excrete waste products mainly through
simple diffusion.
2. Excretion in plant is mainly done through thecell wall and stomata.
3. Mineral salts such as calcium carbonate and
calcium oxalate are retained in the plant ascrystals.
4. Minerals such as silicon salts are deposited in the
leaves to strengthen the leaf blade. 5. Nitrogenous waste products are removed when
plants shed their leaves, flowers or bark.
6. Most nitrogenous wastes are very poisonous.
7. Some excretory products of plants are usefulto humans such as: morphine, opium, cocaine,
tannins and oils.
CHAPTER 4
Reproduction 4.1 Understanding Sexual and Asexual
Reproduction
1. Reproduction is a process of producing new
individuals by living organisms.
2. Importance of reproduction:(a) To increase the number of individuals of the
same species.(b) To ensure certain species does not become
extinct.
3. Types of reproduction:
Vas deferens
Urethra
Penis
ScrotumTestis
Seminalvesicle
Prostategland
Seminal vesicle
Prostate gland
Epididymis
Penis
Testis Scrotum
Urethra
Vas deferens
4.2 Male Reproductive System
Organ Function
Testis ( plural :testes)
• Produces sperms (the malegametes)
• Produces male sex hormones
Scrotum • Holds and protects the testes
Sperm duct(vas deferens)
• Transports sperms from thetestes to the urethra inside
the body
Urethra • Allows sperms to flow out of
the body
Penis • Transfers semen into vagina
during copulation
Seminalvesicles
• Secrete fluid which containsnutrients for the sperms
1. Sperm:
(a) It is the male sex cell.
(b) It is produced by the testes.(c) It is also the smallest cell in the males’
body.
(d) It is shaped like a tadpole, which has a head,neck, middle piece and tail.
(e) The head contains a nucleus which has
genetic material.(f) The tail helps the sperm to move or swim in
the female reproductive system. 2. Males reach puberty at 12 to 14 years old, which
is later than girls.
3. There are physical, emotional and physiologicalchanges during puberty.
4. The testes start to produce sperm and male sex
hormones during puberty.
Reproduction
AsexualSexual(Involving the male and the female gametes)
Binary fission
(bacteria)
Regeneration
(planaria)
Budding
(yeast)
Spore formation
(moss, ferns and fungi)
Vegetative
reproduction
Animals(sperm and ovum)
Plant(pollen grainand ovule)
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4.3 Female Reproductive System
Oviduct (Fallopian tube)
Ovary
Uterus
Cervix
Vagina
(c) Fertile phase / ovulation phase (day 12 to 16)
(d) Premenstrual phase (day 17 to 28) 6. Women of about 50 years of age undergo
menopause when their menstruation stops.
4.5 Fertilisation and Pregnancy
1. Fertilisation is the fusion between the sperm and
the ovum. 2. Development of an embryo into a foetus until
birth:
Sperm Ovum
Zygote
Embryo
Foetus
Baby
Fertilisation
Implantation
Childbirth
Oviduct (Fallopian tube)
Cervix
Urethra
Vagina
Uterus
Ovary
1. Ovum ( plural : ova):
(a) It is the female sex cell.(b) It is produced by the ovary.
(c) It is the largest cell in the females’ body.
(d) It is spherical in shape, which contains anucleus and cytoplasm.
(e) The nucleus contain genetic material.
(f) It cannot move by itself.
4.4 Menstrual Cycle
1. Menstrual cycle is the changes in a woman’s ovary
and uterus over 28 days. 2. Menstrual cycle involves ovulation and
menstruation which happen regularly each
month. 3. Ovulation happens when an ovary releases a
mature ovum.
4. Menstruation is the shedding of the uterine walland blood through the vagina.
5. Menstruation can be divided into four stages:(a) Menstruation phase (day 1 to 5)
(b) Repair phase (day 6 to 11)
Organ Function
Ovary • Produces ova (the femalegametes)
• Produces female sex hormones
Fallopiantube (oviduct)
• Place of fertilisation
Uterus
(womb)
• Place for the implantation of
zygote• Place where the foetus
develops and grows
Cervix • Widens during childbirth
Vagina (birth
canal)
• Place where the sperms are
deposited during copulation• Baby is born through this
birth canal
Ovary produces an ovum (ovulation)
Fallopian tube
The ovum is fertilised (fertilisation)
Embryo attaches to
uterine wall (implantation)
Embryo moves
towards uterus
Uterus
Ovary
An embryo is formed
A zygote is formed
Eight-cell
stage
Four-cell
stage
Two-cell
stage
4.6 Importance of Prenatal Care
1. Pregnant women need to take enough nutritiousfood and have a balanced diet.
2. Pregnant women should avoid smoking, taking
alcohol or drugs.
4.7 Importance of Research in HumanReproduction
1. Sterility (infertility) is the inability to produce
children.
2. Methods to overcome sterility:
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2. Germination happens when the embryo grows
into a seedling. 3. Seeds need air, water and suitable temperature
to germinate.
4.12 Vegetative reproduction in Flowering
Plants
1. Vegetative reproduction is a method of producingnew plants from any vegetative parts of theparent plant.
2. Vegetative reproduction is an asexual
reproduction . 3. Vegetative parts that can reproduce are: stem,
leaf and root.
4. Tissue culture and stem cuttings are techniquesused to produce new plants.
CHAPTER 5
Growth
5.1 Human Growth Pattern
1. Growth is an irreversible and permanent process
in living things.
2. Growth in humans can be determined bymeasuring the height and weight.
3. Growth curve is divided into five stages:
(a) Infancy (d) Adulthood(b) Childhood (e) Old age
(c) Adolescence
(a) Drug treatment (such as hormones)
(b) Surgery(c) In vitro fertilisation (IVF)
3. Methods for birth control (contraception):
(a) Contraceptive pills(b) Rhythm method (natural method)
(c) Using a condom
(d) Using a diaphragm(e) Intrauterine contraceptive device (IUCD)
(f) Vasectomy – sperm ducts cut and tied(g) Ligation (tubectomy) – oviducts cut and tied
4.8 Sexual reproductive System of Flowering Plants
1. Struture of a flower:
Anther Filament
Stamen
Flower
Pistil
Ovary Stigma Style
Pollen grain Ovule
Petal
Anther
Filament
Stamen
Nectary
Receptacle Pedicel
Sepal
Stigma
Style
Pistil
OvaryOvule
Structure Function
Ovary To protect the ovule
Ovule Contains ova (the female gametes)
Anther Contains pollen grains (the male gametes)
Filament To support anther
4.9 Pollination
1. Pollination is the transfer of pollen grains fromthe anther to the stigma.
2. Self-pollination and cross-pollination:
4. Agents of pollination:
(a) Wind (c) Insects
(b) Animals (d) Water
4.10 Development of Fruits and Seeds in Plants 1. Fertilisation occurs when the male gamete fuses
with the ovum in the ovule. 2. A zygote is formed when the ovum is fertilised
by the male gamete.
3. After fertilisation, the ovule will develop into aseed and the ovary become the fruit.
4.11 Germination of Seeds
1. A seed is made up of an embryo and a foodstore wrapped in a testa (seed coat).
Infancy
Slowgrowth Rapid
growth
Rapidgrowth
Minimalgrowth Negative
growth
0 3 13 20 65 Age (years)
H e i g h t ( c m )
AdolescenceChildhood
Old ageAdulthood
Structure Function
Sepal To protect flower during the bud stage
Petal To attract insects or animals
Stamen The male reproductive part
Pist il The female reproductive part
Stigma To receive pollen grains
Style To support stigma
Stigma
AntherPollen grains
Pollen grains
One plant Another plant of
the same species
Key:
Self-pollination Cross-pollination
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CHAPTER 6
Land and Its Resources
6.1 Minerals in the Earth’s Crust
1. Minerals are solid elements or compounds found naturally.
2. Elements present in various minerals:
Oxide Carbonate Sulphide Silicate
Element Cassiterite Haematite Calcite Malachite GalenaIron
pyriteChinaclay
Calciumsilicate
Tin
Iron
Calcium
Copper
Lead
Aluminium
Silicon
Oxygen
Carbon
Sulphur
3. Properties of minerals:
Properties Description
Hardness Most mineral are hard
Solubility
in water
Most minerals are insoluble in
waterAction of
heat
• Most metal oxides are stable
• Metal sulphides break downinto metal oxide and release
sulphur dioxide gas
6.2 Reactions Between Metals and Non-metals
1. Metals react with non-metals at different ratesto form stable compounds:
(a) Metals react with oxygen to form metaloxide
(b) Metals react with sulphur to form metal
sulphide
Metal
Reaction
rate withoxygen
Reaction
rate withsulphur
Magnesium Very fast Very fast
Aluminium Very fast Very fast
Zinc Fast Fast
Iron Fast Fast
Copper Slow Slow
6.3 Silicon Compounds
1. Silicon is the second most abundant element in
the Earth’s crust.
2. Silicon always exists in the form of compounds
such as silicas and silicates. 3. Silica is silicon dioxide, which consists of silicon
and oxygen.
4. Silicate is made up of silicon, metal and oxygen. 5. Properties of silicas and silicates:
(a) Insoluble in water
(b) Do not react with acid(c) Do not break down when heated
(d) Very stable and are not eroded easily
6.4 Calcium Compounds
1. Properties of calcium carbonate:
(a) Insoluble in water
(b) Reacts with dilute acids to produce salt, waterand carbon dioxide
(c) Breaks down into calcium oxide and carbondioxide when heated
2. Quicklime (calcium oxide) is formed when calcium
carbonate is heated strongly. 3. Slaked lime (calcium hydroxide) is formed when
calcium oxide is added with some water.
4. Limewater (calcium hydroxide solution) is formedwhen slaked lime is added with more water.
6.5 Natural Fuel Resources and Their Importance
1. Fossil fuels include petroleum, natural gas andcoal.
2. Petroleum:
(a) Formed from organism remains buried insediment under heat and high pressure.
(b) It contains many types of hydrocarbons which
can be separated by fractional distillation.(c) The components of petroleum produced by
fractional distillation are called fractions (or
distillates).(d) Different fractions are obtained due to
different boiling points.• the greater the boiling point, the darker
the colour of the fractions
• the greater the boiling point, the moreviscous the fractions
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CHAPTER 7
Electricity
7.1 Electrostatics
1. Electrostatics is the study of static electrical
charges.
2. Electrical charges can be produced through
friction between two objects. 3. Matters are made up of small particles called
atoms.
Structure of an atom
4. An atom has two charged particles:(a) Electrons, which have a negative charge (–)
(b) Protons, which have a positive charge (+)
5. Neutrons in an atom have no charge becausethey are neutral.
6. An atom becomes positively charged when itloses electrons.
7. An atom becomes negatively charged when it
gains electrons.
7.2 Electricity
1. Electricity is a form of energy. It is also called the
electrical energy.
2. Electrical energy can be generated by generatorsand electric cells.
3. Current, voltage and resistance:(a) Current
– the rate of flow of charges. – flows from the positive terminal to thenegative terminal of a battery.
The flow of electric current and electron
(b) Voltage – the electrical force needed to move
electrical charges from one point to other
in a conductor.(c) Resistance
– characteristic that resists the flow of electric
current in a conductor.
7.3 Electric Current, Voltage and Resistance
1. Measuring current (symbol: I ):
– connect an ammeter in series with otherelectrical components in a circuit.
– the deflection of the pointer of the ammeter
shows the value of current flowing throughthe components.
– the SI unit for electric current is ampere
(symbol: A). 2. Measuring voltage (symbol: V ):
– connect a voltmeter in parallel to otherelectrical components in a circuit.
– the deflection of the pointer of the voltmetershows the value of voltage across thecomponents.
– the SI unit for voltage is volt (symbol: V).
3. The SI unit for resistance (symbol: R) is the ohm(symbol: Ω).
7.4 The Relationship Between Current, Voltageand Resistance
1. Resistor is an electrical component that resists
the flow of electric current.
• the greater the boiling point, the more
soot is produced when the fractions areburnt
• the greater the boiling point, the harder
the fractions burn
Product of
distillationUses
Petroleum gas Cooking gas
Petrol (gasoline) Fuel for vehicles
Naphta For making plastics
and polyvinyl chloride(PVC)
Kerosene Fuel for aircraft
Diesel oil Fuel for lorries and
buses
Lubricating oil Lubricants for
machines
Fuel oil Fuel oil for ships
Bitumen To seal roads
3. Natural gas:(a) consists of 90% methane, 10% of mixture of
ethane, propane, butane and pentane.
(b) It is usually found together with thepetroleum.
(c) It is used as fuel source and to producefertilisers.
4. Coal:
(a) Made up of carbon, oxygen, nitrogen and
sulphur.(b) It is formed from plant remains that grew in
swamps.
Current
(a) Direction of electric current flow
Electron flow
(b) Direction of electron flow
Electron (negatively charged)
Proton (positively charged)
Neutron (no charged)
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2. Advantages of a series circuit:
(a) When more cells are added to the circuit,the voltage and current increase. Hence, the
bulbs glow brighter.
(b) Bulbs light up with equal brightness becausethe current flows through each bulb is the
same.
3. Disadvantages of a series circuit:(a) If one of the bulbs is fused (burned out), the
other bulbs will not light up.(b) The brightness of the bulbs decreases when
more bulbs are connected in series, because
the electrical energy is shared by morebulbs.
7.7 Parallel Circuit
1. Current, voltage and total resistance in parallel
circuit: 2. Advantages of a parallel circuit:
(a) When one of the bulbs is burned out, theother bulbs will still light up.
(b) Each electrical component can be controlled
by separate switches.(c) All bulbs will light up with the same
brightness.
I = I 1 + I
2
V = V 1 = V
2
1 1 1
— = — + — R R1 R2
3. Disadvantage of a parallel circuit:
(a) When more bulbs are connected in parallel,the dry cells will become weak quicker.
7.8 Magnetism
1. Magnetism is the properties and effects ofmagnetic substances.
2. Ohm’s Law:
– the current flowing through a conductor isdirectly proportional to its voltage.
Voltage (V )Resistance (R) = —————– Current ( I )
– the greater the resistance, the smaller the
current.– increasing the voltage supplied will increase
the current in the circuit.
7.5 Electric Circuits
1. An electric circuit is a path which allows an
electric current to flow through.
2. A simple electric circuit is made up of 3components:
(a) A cell (a source of electrical energy)
(b) A bulb (a resistor)(c) Connecting wire (a conductive path)
An electric circuit
3. Symbols of electrical components:
Electricalcomponent
Symbol
Electric cell
Battery (morethan one cell)
Switch
Bulb
Resistor
Dry cell
Wire
Light bulb
or
or
Electrical
componentSymbol
Rheostat(Variable
resistor)
Fuse
Galvanometer
Voltmeter
Ammeter
4. Comparison between series and parallel
circuits:
Series circuit Parallel circuit
• Has only one path
for current to flow
through• Light bulbs do not
glow as bright asthose connected in
parallel
• Has more than one
path for currect to
flow through• Light bulbs glow
brighter thanthose connected in
series
• If one light bulbburns out, the
circuit becomes
incomplete. Hence,other light bulbs
will not light up.
• If one light bulbburns out, other
light bulbs will still
light up.
7.6 Series Circuit
1. Current, voltage and total resistance in seriescircuit:
I = I 1 = I
2 = I
3
V = V 1 + V
2 + V
3
R = R1 + R
2 + R
3
V
V
V
V 1
I 1
R1
R2I 2
V 2
V
I
V V V
V
V 1 V 2
V
I I 1R1 I 2R2 I 3R3
V 3
G
or or
V
A
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(c) Gas turbine generator
(d) Diesel power plant
(e) Nuclear power plant
8.2 Transformers
1. A transformer is a device for changing the voltage
of an alternating current. 2. An alternating current (symbol: a.c.) flows back
and forth, reversing its direction.
2. Magnetic field is the area around a magnet where
a magnetic force can be detected. 3. The magnetic field of a magnet can be represented
by lines, called magnetic field lines.
4. The magnetic field lines have a certain patternand direction.
(a) The pattern of the magnetic field lines can
be shown by using iron filings.
(b) The direction of the magnetic field lines can
be detected by using a compass.
5. Characterstics of magnetic field lines:
(a) Run from the north pole to the south poleof the magnet.
(b) Do not cross one another.
7.9 Electromagnetism
1. Electromagnetism refers to the properties and
effects of electromagnets produced by electric
current. 2. An electromagnet is a magnet that is produced
by the flow of electric current.
(a) Without electrical energy, an electromagnetloses its megnetism.
(b) An electromagnet is a temporary magnet.
3. A straight line conductor carrying current producesa concentric magnetic field lines around it.
Controlrods
Concrete wall
Steamturbine
Condenser
ElectricalOutput
Pump
PumpPump
Water
PumpPump
Water
Steam
generator
Reactor
38ºC27ºC
Steam
Diesel engine Generator
electriccurrent
CardboardMagnet
placed
under the
cardboard
Iron filings
Compass Magnetic
field lines
N
S
CHAPTER 8
Generation of Electricity
8.1 The Generation of Electrical Energy
1. Types of generators:(a) Hydroelectric power plant
(b) Thermal generator
Copper wire
Card
Retortstand
Power pack
Switch
Compass
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3. Types of transformers:
(a) Step-up transformer
– To increase the output voltage.
– The secondary coil has more turns than
the primary coil.
(b) Step-down transformer
– To reduce the output voltage.
– The secondary coil has less turns than the
primary coil.
a.c.inputvoltage
a.c.outputvoltage
Soft iron core
Primary coil Secondary coil
a.c.inputvoltage
a.c.outputvoltage
Soft iron core
Primary coil Secondary coil
8.3 Electrical Power Transmission and Distribution System
Powerstations
Step-up
transformerSwitchzone
National
GridNetwork
Mainsubstation
(Step-down
transformer)
Branch
substation33 kV
Heavy
industrial area
11 kV 132 kV/ 275 kV/ 500 kV
132 kV/ 275 kV/ 500 kV
132 kV/ 275 kV/ 500 kV
Branch
substation 11 kV
Light
industrial area
Branchsubstation 240 V
Residentialarea
Branch
substation 415 V
Shopping
complexes
1. National Grid Network is a system of high voltage
circuits that connects the main power stations. 2. Advantages of National Grid Network:
(a) Ensures continuous and uninterrupted
electrical power supply to the consumers.(b) Reduces the operational cost of electrical
energy transmission.
(c) Prevents wastage of electrical energy.
8.4 Electrical Power Supply and Wiring system inHomes
1. Homes are supplied with 240 V alternatingcurrent (a.c.).
Part Function
Mains
fuse
Breaks the circuit when current
exceeds a safe value
Mains
switch
Cuts off electrical power supply
from the mains when electricity
is not neededCircuit
breaker
Cuts off the electric current that
flows under abnormal conditions
Live wire Carries the electric current fromthe substation to the house
Neutralwire
Carries the electric current fromthe house back to the substation
Earth
wire
Connects an electrical appliance
to the earth or ground
Electricmeter
Measures the amount ofelectricity used
2. Our home uses single-phase wiring system. 3. The commercial and industrial areas use three-
phase wiring system. 4. 3-pin plug:
Distribution systemTransmission systemGeneration Cable
Neutral wire
Earth wire
Cover removed Fuse
Cover
Live wire
11 kV
240 V/ 415 V 33 kV 33 kV
33 kV 11 kV
Heavyindustrialarea
T r a n s m i s s i o n
s y s t e m
D i s t r i b u t i o n
s y s t e m
Lightindustrial area
HospitalShoppingcomplex
Residentialarea
132 kV/ 275 kV/ 500 kV
B
C
Transmission overlong distances
D
E E
A
A Components:A – Power stationB – Step-up transformerC – National Grid NetworkD – Step-down transformerE – Branch substation
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8.5 Cost of Electrical Energy Usage
Energy used (J) 1. Power (W) = ———————– Time (s)
2. Power (P ) = Voltage (V ) × Current (I )
3. Energy (kWh) = Power (kW) × Time (h)
1 unit of electrical energy = 1 kWh
8.6 Fuse and Earth Wire
1. Fuse and earth wire are protection devices.
(a) Fuse breaks off the electrical circuit.(b) Earth wire ensures the leakage of current
flows to the ground. 2. Function of the fuse:
(a) A fuse has a piece of short wire which has
a low melting point.(b) When excess current flows through it, the
wire in the fuse melts and disconnects the
current.
3. Types of fuses:
(a) Replaceable wire fuse(b) Cartridge fuse
4. Fuses have different ratings, according to the
maximum current they can carry. For example,1 A, 2 A, 3 A, 5 A, 10 A and 13 A.
8.7 Safety Precautions in the Use of ElectricalEnergy
1. Damaged appliances must be repaired by qualifiedelectrician only.
2. Avoid overloading a power point. 3. Avoid touching switches, wires or plugs with
wet hands, as this may cause electric shock or
electrocution. 4. Install Earth Leakage Circuit Breaker (ELCB) and
Miniature Circuit Breaker (MCB) in home wiring
system for additional protection against electricalaccidents.
8.8 Conserving Electrical Energy
1. We need to conserve electrical energy to preventwastage.
2. Ways to conserve energy:
(a) Use fluorescent lamps instead of incandescentlight bulbs.
(b) Use energy efficient electrical appliances.
(c) Use the washing machine with a full load.(d) Switch off electrical appliances when they
are not in use.
CHAPTER 9
Stars and Galaxies
9.1 The Sun
1. The Sun is a star that is closest to the Earth. 2. Characteristics of the Sun:
(a) It is the centre of the solar system.(b) It is the only star in the solar system.(c) It is mainly made of hydrogen (70% to 80%)
and helium.
3. Structure of the Sun:
(a) Corona (outermost layer) is seen only during
a total solar eclipse.(b) Chromosphere (middle layer) appears reddish
during a solar eclipse.
(c) Photosphere (innermost layer) is the Sun’ssurface as seen from the Earth. It has sunspots,
prominences and solar flares.(d) Core (centre of the Sun) is the place where
nuclear fusion takes place, that is, hydrogen is changed into helium, releasing a lot ofenergy.
(e) Sunspots (dark patches) are cooler and they
can cause changes in the Earth’s climate, suchas extreme drought.
(f) Prominences are ‘giant flares’ which are huge
columns, extending thousands of kilometresfrom the surface. It produces solar wind and
causes aurora.(g) Solar flares are huge clouds of hydrogen that
explode violently on the Sun’s surface. They
Contact
Holder
Fuse wire
Contact
Metalcap Fuse wire
Glass tube
Cartridge fuse
Replaceable wire fuse
3-pin plug
Live
wire
Neutral
wire
Earth
wireFuse
Carriescurrentfrom the
substation
to thehouse
Carriescurrentfrom the
house
backto the
substation
Carriesleakagecurrent
from the
appliancesto the
Earth
Preventsexcessivecurrent
flowing
into theappliance
and
damaging it
• A 3-pin plug carries electric current from apower station to an appliance in use, and
then returns it to the substation.
• A 3-pin plug also acts as a safety device toprotect an appliance in use from getting
damaged.
Corona
Chromosphere
Photosphere
Core
Prominence
Sunspots
Solar flare
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also change the Earth’s climate and affect
the telecommunication systems on Earth.
9.2 Stars and Galaxies in the Universe
1. Stars:
(a) Made up of dust and gases (such as hydrogen
and helium).
(b) Generate heat and light through nuclearfusion.
(c) Differ in size, brightness, colour and
temperature.
2. Arrangement of stars in ascending order oftemperature:
Red→ Yellow→ White→ Whitish-blue→ Blue
3. Arrangement of stars in ascending order ofsize:
Neutron star → White dwarf star → Dwarf star→ Giant star → Supergiant star
4. Formation of stars:(a) Stars are formed from nebulae ( singular :
nebula), which are made of clouds of dustand gases.
(b) The nebula contracts when the gases and
dust exert a strong gravitational force oneach other.
(c) Further contraction causes the ball to become
denser until hydrogen atoms fuse to formhelium atoms – a nuclear fusion reaction.
(d) The reaction causes the temperature to riseand causes the star to expand.
(e) The balance between the contraction andexpansion of star will form a stable star, suchas the Sun.
5. The death of stars:
(a) When nuclear fusion no longer takes place,the size of the core of the star will reduce.
(b) The size of a star determines its lifespan.
(c) Massive stars have longer lifespan thansmaller ones.
(d) The death of a medium-sized star:
Red giant → White dwarf → Black dwarf
(e) The death of a large star:
Red giant → Supergiant → Supernova →
Neutron star
(f) The death of a super-large star:
Red giant → Supergiant → Supernova →
Black hole
6. Galaxies:
(a) Are collection of billions of stars, planets, dustand gases held together by a gravitational
force
(b) Types of galaxies:
Types Description
Elliptical-shapedgalaxy
• It has a diameter between3000 and 10 000 light years.
• It looks like a smooth,
round and oval-shaped disc,and has no arms.
• It is the brightest at thecore and gradually fadestowards the edge.
• It is made up of old yellow
stars and does not containgas and dust, so new stars
are not formed.• Example: M87 in the centre
of Virgo cluster.
Spiral-shapedgalaxy
• It has a diameter of about20 000 to 100 000 light years.
• It is disc-shaped and made
up of stars gathering ina whorl with spiral arms
at the edges. These arms
contain dust and gases.• It has a bright centre. Its
centre has older stars. Itsarms have younger stars,
while dwarf stars and
nebulae. The arms rotatearound its centre.
• Example: The Milky Way,
Andromeda
Types Description
Irregular-shapedgalaxy
• It has a diameter between25 000 and 32 000 light
years.
• It does not have a definitepattern or shape.
• It exists in various different
forms and is usually madeup of young stars that are
very hot.• Example: Large Magellanic
Cloud
7. The Milky Way:(a) It is a spiral-shaped galaxy.
(b) The solar system is located in the MilkyWay.
8. The Universe:
(a) It consists of all the matter, energy and spacethat exist.
(b) It has billions of galaxies, stars, planets and
particles.(c) Its size is infinitive and unknown.
9.3 The Universe as a Gift from God
1. The Universe is a unique creation of God. 2. Everything that exists in the Universe is not
permanent: Stars are born and die out, new stars
are formed to replace them.
CHAPTER 10
Space Exploration
10.1 Developments in the Field of Astronomy and
Space Exploration
1. Astronomy is the study of objects in the
Universe. 2. The Greeks:
(a) The first people to study astronomy.
(b) First to declare that the Earth is spherical,and the orbits of the planets are circular.
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3. The Islamic astronomers studied the rotation of
the Earth and the eclipses of the Sun and theMoon.
4. Other developments:
(a) Hans Lippershey invested a telescope.(b) Galileo Galilei was the first man to observe
objects in space with a telescope.
(c) Yuri Gagarin was the first person in space.
(d) Neil Armstrong was the first human to setfoot on the Moon.
(e) Aristotle believed wrongly that the Earth was
the centre of the Universe.
(f) Claudius Ptolemy supported Aristotle’sbelief that the Earth was the centre of the
Universe.
(g) Nicholas Copernicus (The father of themodern astronomy) stated that the Sun is
the centre of the solar system.
5. Technology used in space exploration:(a) Space telescope (such as Hubble Space
Telescope) – helps scientists to discoverdistant objects(b) Space probes – send images and data back
to Earth for analysis(c) Space station – allows scientists to work in
space for a long period of time
(d) Space shuttles – carry astronauts to repairand retrieve damaged satellites in space
(e) Satellites – unmanned devices which are
placed in the orbit of the Earth to carry outcertain functions.
Space telescope
Space probe
Space station
Space shuttle
Satellite
6. Types of satellites:(a) Communication satellites – enable instant
radio and telephone communication, livetelecast and Internet applications(b) Weather satellites – enable meteorologists to
predict weather hazards such as hurricanesand floods
(c) Navigation satellites – guide ships and
aircraft(d) Military satellites – improve national security,
defence and spying systems
(e) Environmental satellites – detect world’sresources
7. Remote sensing is the means of using satellites
to study the conditions on Earth from space.
8. Remote sensing can be used in geology,agriculture, forestry, disaster management andnational security management.
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