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Diva Parekh
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PHYSICS
TOPIC 1: MEASUREMENTS 
Mass (kg)
Density (kg/m3) = Volume (m3)
A Period of a pendulum = the time taken for one swing (from left to right and back)
Fundamental physical quantities [all other quantities are derived from these}:
1.
2.
3.
4.
Mass (kg)
Time (s)
Temperature (K)
Distance (m)
5. Electrical current (A)
6. Amount of substance (mol)
7. Light intensity (cd)
Temperature Conversions:


Temperature (°C) = 273 + Temperature (K)
°C
°F – 32
=
5
9
Scalars and Vectors:


Scalar quantity = a physical quantity with only magnitude  e.g. speed, time, mass,
density, temperature
Vector quantity = a physical quantity with both magnitude and direction  e.g. velocity,
force, weight, acceleration
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TOPIC 2: FORCES AND MOTION 
Speed (m/s) =
Distance (m)
Time (s)
Velocity (m/s) =
5
(conversion: 1km/h = 18 m/s)
Displacement (m)
Time (s)
Difference between distance and displacement 
Displacement
Vector quantity
Shortest possible distance between final and
initial position of an object
Found by calculating the area under a
velocity/time graph
Distance
Scalar quantity
Actual distance travelled by an object
Found by calculating the area under a
speed/time graph
Acceleration (m/s2)  rate of change of velocity
=
Final velocity (m⁄s) – Initial velocity (m⁄s)
Time (s)
[-ve acceleration = deceleration]
Acceleration of free fall = 10m/s2
Other formulae 
1. a =
v–u
t
1
2. s = ut + 2 at2
3. s =
u+v
2
×t
***Acceleration = a; Time = t; Displacement/distance = s; Final velocity = v; Initial velocity = u
Difference between mass and weight 
Mass (kg)
Scalar quantity
How much matter an object is composed
of
Doesn’t change
Weight (N)
Vector quantity
The force of gravity that acts on an object
Remains uniform until within a certain field of gravity
but changes when taken out
Acts vertically downward
Property of an object to resist change in
motion
Force (N) = mass (kg) × acceleration (m/s2)  the greater the mass of an object the smaller the
acceleration it is given by a particular force
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Terminal velocity is when the air resistance is balanced by the weight of an object  the object
begins to fall at a steady rate [constant speed/no acceleration]
Law of Inertia 
In the absence of any external unbalanced force, an object at rest will remain at rest while an
object moving at a constant speed will continue moving at the same speed.
Momentum is proportional to inertia. Any moving body will have momentum.
Force ∝
Change in momentum
Time taken
(rate of change of momentum)
Momentum (kgm/s) = Mass (kg) × Velocity (m/s)
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TOPIC 3: FORCES AND PRESSURE 
Forces and extension 
Length of a stretched spring = original length + extension
Hooke’s Law  the extension of a spring is proportional to the force applied to it provided that
the limit of proportionality is not exceeded
Limit of proportionality  a point after which the spring becomes permanently deformed and
does not return to its original state. Hooke’s Law does not apply after this point. The spring
continues to extend irregularly until it breaks/the breaking point is reached. F = kx [where F is the
force and x is the extension].
Elasticity is a property that implies the ability of an object to regain its original shape on removal
of the force deforming it.
Plasticity refers to the ability of an object to retain the new shape gained due to the deforming
forces acting on it.
Moment of a force 
Moment of a force (Nm) = force (N) × perpendicular distance from pivot to force (m)
Turning force needed is the least when the force is furthest from the pivot and at a right angle to
it.
During equilibrium/Balanced beam 
Total clockwise moment = Total anticlockwise moment
Total weight = sum of all forces + weight of the beam itself
Contact force = Total weight
Centre of Mass  the point in an object where it behaves as if its entire mass is concentrated
around a point
If a pivot is placed at the center of mass there is no movement.
A weight causing a clockwise moment is always balanced by another weight causing an anti
clockwise moment.
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Pressure 
Pressure is the force per unit area acting perpendicular to a surface
Pressure (Pa or N/m2) =
Force (N)
Area (m2 )
Pressure in fluids (Pa or N/m2) = Height (m) × Density substance (kg/m3) × Gravity (N/kg)
Gas Pressure (Boyle’s Law) 
Pressure (Pa) ∝ Volume (m3) on condition that Temperature (K) is constant
p = kV ∴ k = pV [where k is a constant]
The volume of a fixed mass of gas is inversely proportional to its pressure, provided its
temperature remains constant.
P1V1 = P2V2 [Provided temperature is constant]
V1
T1
P1
T1
=
=
V2
T2
P2
T2
[Provided pressure is constant]
[Provided volume is constant]
***P = pressure; T = temperature; V = volume
Mercury Barometer 
Used to measure atmospheric pressure: consists of a long glass tube (80cm) filled with mercury
and inverted into a trough (done carefully to prevent air entering). The length of the mercury
column is proportional to atmospheric pressure.
Atmospheric pressure at sea level = 1.01352 × 105
Manometer 
Functions using the same principle as barometers: used to compare difference in pressure of two
gases
 Contains a U-tube holding a fixed amount of a certain liquid (generally mercury – density =
13.5 g/cm3 OR 13534 kg/m3)
 When the gas supply tanks contain the same gas, the liquid is at the same level in both
sides
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 When different gases are placed into the tanks, the gas with the higher pressure pushes
down on the liquid
 The difference in pressure can be found using the difference in height of the liquid columns
on both sides using the formula for pressure in fluids (height is found, density of the liquid
and gravity is already known)
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TOPIC 4: FORCES AND ENERGY 
Forces (Newtons or N) cause changes in motion or shape of an object
Types of forces 
Friction opposes motion
Air resistance/Drag is the force of friction when an object moves through air or water
Upthrust is the upward push of a liquid or gas on an object
Weight is the pull of gravity of an object:
Weight (N) = Mass of object (kg) × Force of gravity (N/kg)
Force of gravity on Earth = 10N/kg
Contact force is exerted by a surface and opposes weight
Resultant Force is the single force that has the same effect as two or more forces
Centripetal Force acts towards the center of a circle on a body moving in a circular path (a force
acting on a moving body at an angle to the direction of motion, tending to make the body follow a
circular or curved path)
Joules (J) is the unit of energy
Forms of Energy 


Chemical Energy is energy stored in chemical bonds of compounds. It is released when they
are broken down. It is found in fuels, batteries, and in the human body.
Kinetic Energy is the energy possessed by a moving object. It can be found by the formula:
1
K.E. = 2 mv2 [K.E. = kinetic energy (J); m = mass (kg); v = velocity (m/s)]



Gravitational Potential Energy is the energy stored in an object above the earth’s surface (or
generally can be taken as any surface). It is the energy that causes objects to fall down. It can
be found by the formula:
G.P.E. = mgh [G.P.E. = gravitational potential energy (J); m = mass (kg); g = gravity (N/kg); h =
height aboveground (m)]
Electrical Energy is the energy transferred by moving electrons in a circuit. It is a good way of
transferring energy since it is easily converted to different forms.
Nuclear Energy is the energy stored in the nucleus of atoms that is released when the atom is
broken down or split. Radioactive materials also contain nuclear energy.
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




Internal Energy is the energy stored in any object. It is the energy of the vibrating or moving
atoms in the object.
Thermal/Heat Energy is energy travelling from a hotter (molecules have a higher average
kinetic energy) to a cooler (molecules have a lower average kinetic energy) object.
Light Energy is a form of energy transferred through radiation.
Sound Energy is transferred in the form of vibration through the air.
Strain Energy is energy stored by an elastic object when deformed. This energy helps the
object return to its original state.
Law of Conservation of Energy  Energy can neither be created, nor destroyed. It can only be
converted to different forms.
The total amount of energy before and after any conversion is constant, though some of this
energy may have been wasted.
Energy Efficiency
The efficiency of an energy conversion is the fraction of the energy that results in the desired
form.
Efficiency of an object (%) =
Useful Energy Output (J)
Total Energy Input (J)
× 100
Work and Power 
Work done (J) = Energy transferred (J) OR ΔW = ΔE
Work done (J) = Force (N) × Distance moved in the direction of the force (m) OR W = F × d
Power (W) =
Work done (J)
Time taken (s)
OR P = W/t
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Energy Resources 
Renewable (inexhaustible resources that can be replaced after use) 
 Hydropower: Potential energy of water stored at heights in dams is released, converting it into
kinetic energy that turns a generator.
 Geothermal Energy: The large thermal energy content inside the earth’s crust is harnessed by
pumping water down to the rocks. Thermal energy is transferred from the rocks to the water,
which boils. Kinetic energy present in high-pressure steam that results is used to turn a
generator.
 Solar Energy: In sunny countries, solar panels are used to absorb thermal energy directly from
the sun. The thermal energy is used to heat water and form steam, whose kinetic energy turns
a generator.
 Wind Power: Kinetic energy of the wind is used to turn windmills that also function as turbines
to turn a generator.
 Wave/Tidal Power: The kinetic energy from wave movements is used to spin turbines
connected to a generator.
 Biomass Fuels: Chemical energy stored in organic matter is released by burning, generating
thermal energy that fuels rural households. Can also be considered as non-renewable since
some types of biofuels are exhaustible.
Non-renewable (exhaustible resources that can’t be replaced after use) 
 Fossil Fuels: Chemical energy stored in hydrocarbons is released by burning. Their thermal
energy is used to heat water to form steam, whose kinetic energy turns a generator.
 Nuclear Power: The radioactive decay of some elements such as uranium is speeded up using
the process of nuclear fission. This creates a chain reaction that releases large amounts of
thermal energy from the atoms’ nuclear energy. Their thermal energy is used to heat water to
form steam, whose kinetic energy turns a generator.
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Advantages and Disadvantages 
Energy Resource
Hydro-power
Advantages
Renewable
Clean – no carbon emissions
Wind power
Renewable
Clean – no carbon emissions
Wave power
Renewable
Clean – no carbon emissions
Solar power
Renewable
Clean – no carbon emissions
Geothermal
energy
Renewable
No carbon emissions
Can be used directly and
easily
Relatively cheap usage
Renewable
Easily available
Biomass fuels
Fossil fuels
Nuclear power
Disadvantages
Depends largely on location
Building dams causes drastic environmental
changes
High initial set-up costs
Need a large area/scale
Irregular source
High maintenance costs
Inefficient due to irregular wave patterns
Depends largely on location
High maintenance and very high installation
costs
Works only during the day and during certain
types of weather
High initial costs
Requires a very large scale/area
Not a widely available source
Suited only for particular regions
Can release harmful gases from deep in the
earth
High initial costs
Carbon emissions pollute the air and
contribute to global warming
High production costs
Non-renewable
Carbon emissions pollute the air and
contribute to global warming
Difficult and expensive to dispose of
radioactive wastes produced
Could easily go out of control and cause a
health hazard
Uranium mining tends to be difficult
Relatively cheap
Can be used directly and
easily
Very high power output
No carbon emissions
Large reserves of nuclear
fuels are present in the
environment
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TOPIC 5: KINETIC MODEL OF MATTER 
State
Volume
Shape
Solid
Fixed
volume
Fixed shape
Liquid
Fixed
volume
Takes the
shape of its
container
Gas
Expands to
fill its
container
Takes the
shape of its
container
Arrangement of
particles
Packed closely together
in a regular
arrangement
Slightly less closer than
in a solid, but particles
are still in contact with
each other
Widely separated from
each other and do not
come on contact with
each other unless they
collide
Movement of
particles
Vibrate about
a fixed
position
Vibrate and
slide over each
other – fluid
Energy
Vibrational
Vibrational and
translational
Move freely
Vibrational,
around, and
translational
colliding with
and rotational
each other &
the container’s
walls – fluid
Movement of Particles 
Brownian motion: the continuous random movement of a fluid particle
The straight path of a moving particle changes in direction when it collides with other particles or
the walls of the container.
Change of State 
Solid
Melting
Freezing





Boiling or Evaporating
Liquid Gas
Condensing
freezing
All state changes (except evaporation) occur at fixed temperatures
Boiling point = Freezing point
Melting point = Condensation point
At the boiling and melting points, heat energy is not being used to raise the temperature of
the substance, it is used to overcome the attractive forces between the particles to move
them further apart
When solids are heated, they vibrate more strongly, expanding. When they vibrate with a
sufficient strength, the bonds between them are broken, forming a liquid
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 Evaporation and Boiling
Evaporation
Can occur at any temperature (normally below
the boiling point)
Only takes place at the surface of the liquid
No bubbles are produced
Slower process
Temperature of the liquid decreases
Boiling
Occurs at a fixed temperature (boiling point)
Takes place throughout the liquid
Bubbles are produced
Relatively faster process
Temperature of the liquid doesn’t change
Factors affecting evaporation: 1. Temperature: at a higher temperature more of the particles of the liquid are moving
fast enough to escape from the surface
2. Surface area: with a greater surface area, more of the particles are close to the surface
so they can escape more easily
3. Moving air/Draught: when particles escape from the water, they are blown away, thus
maintaining a concentration gradient for more particles to evaporate.
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TOPIC 6: THERMODYNAMICS 
Temperature (K) is a measure of the average kinetic energy of the individual particles of a
substance.
Internal Energy (J) is the total energy of all the particles.
Thermal Equilibrium is when no net energy transfer occurs between multiple surfaces since their
particles all contain the same average kinetic energy.
Measuring Temperature 
1. Thermometers (liquid-in-glass) work on the principle of expansion of liquids with heat. The
Celsius scale is calibrated by first placing the thermometer in melting ice then waiting for it to
reach equilibrium to mark 0°C. the same is done just above boiling water for 100°C. Factors
necessary to form such a thermometer:
Sensitivity is a property wherein a small change in temperature causes a large change in the
liquid column
Linearity is a property wherein the expansion/change in length displayed by the liquid is
proportional to its temperature
2. Thermocouples are devices that give an output voltage that is proportional to the
temperature. They are made from two pieces of wire made of two different metals (normally
copper and iron). The wires are joined to form two junctions. One junction is kept at a fixed
temperature of 0°C (calibrated by placing in melting ice) while the other is placed in the object
whose temperature is to be measured. The difference in temperature is reflected as the
potential difference in voltage between the junctions.
Thermal Expansion  most substances (solids, liquids and gases) expand on heating as the
particles begin to move faster and away from each other.
Heat Capacity 
Heat Capacity of a body is the amount of thermal energy required to raise its temperature by 1°C
or 1K.
Thermal Energy required (J) = Heat capacity (J/K or J/°C) × Change in temperature (K or °C) OR Q =
CΔT
Specific heat capacity of a substance is the amount of thermal energy required to raise the
temperature of 1kg of the substance by 1°C or 1K.
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Thermal Energy required (J) = Mass (kg) × Specific heat capacity (J/kgK or J/kg°C) × Change in
temperature (K or °C) OR Q = mcΔT
Latent Heat 
Latent Heat of a body is the amount of thermal energy absorbed or released during a change of
state.
The specific latent heat of vaporization is the energy required to cause 1kg of a substance to
change its state from liquid to gas at its boiling point.
The specific latent heat of fusion is the energy required to cause 1kg of a substance to change its
state from solid to liquid at its melting point.
Thermal Energy required (J) = Latent heat (J/kg) × Mass (kg) OR Q = mL
Heat Transfer 
 Thermal/Heat energy is only transferred when there is a difference in temperature
 Heat is transferred from a region of higher temperature to a region of lower temperature until
the regions reach thermal equilibrium
Heat Transfer Methods:
1. Conduction is the process by which heat is transmitted through a medium from its hotter part
to its colder part until they are both at the same temperature
 When a part of an object (medium) is supplied with thermal energy, the particles at that
part gain kinetic energy. They vibrate faster and collide with the neighboring particles.
 As the particles collide, kinetic energy is transferred. The less energetic particles gain
kinetic energy, vibrate faster, and collide with other less energetic particles in the colder
part of the object.
 This continues until the heat energy spreads throughout the object.
 Tends to happen more in solids since the particles are closer together.
 Metals are good heat conductors since they contain free electrons, which are not
possessed by non-metals. E.g. Copper, Steel, Aluminum
 Non-metals are poor heat conductors (insulators). E.g. Plastic, Wood, Air
2. Convection is the process by which heat is transmitted from one place to another by the
movement of heated particles in a fluid
 When thermal energy is supplied to a region of the fluid, it expands.
 This region becomes less dense than the surrounding fluid and thus rises.
 The other cooler, denser regions of the fluid sink to replace the less dense fluid.
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
This creates convection currents – the flowing of a liquid or gas caused by a change in
density in which the entire medium moves and carries the heat energy with it.
3. Radiation is a method in which heat energy is transferred from a hotter to a cooler object in
the form of electromagnetic waves, specifically infrared radiation
 Objects tend to absorb as well as emit infrared radiation
 This process can take place in a vacuum; it does not require a medium.
 When emitted radiation reaches an object, heat energy is absorbed, making its molecules
vibrate faster.
 Different objects emit and absorb different amounts of radiation at different rates.
 Good absorbers of heat are also good emitters.
 Other objects that do not absorb heat are termed as reflectors.
 Factors affecting radiation –
Color and texture
Surface area
Temperature difference
Faster radiation
Dull black surfaces
(emitters/absorbers)
Larger
Higher
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Slower radiation
Bright and shiny surfaces
(reflectors)
Smaller
Lower
TOPIC 7: WAVES AND SOUND 
A wave transfers energy through disturbances in its environment – no matter is transferred in the
process.
Types of Waves
A)
B)
Electromagnetic
 Do not need a medium
 Form a full spectrum
 An electric field oscillates
perpendicular to the wave motion
Transverse
 Direction of motion of the oscillating
particles is perpendicular to the
direction of motion of the
wave/energy transfer/disturbance
 Upwards/downwards oscillation
 Can occur in both mechanical and
electromagnetic waves
 Distance/displacement variation
based on that of the mean position
 Example – ripples, all electromagnetic
waves
17
Mechanical
 Need a medium
 Example – sound, springs, water
waves
Longitudinal
 Direction of motion of the oscillating
particles is parallel to the direction of
motion of the wave/energy
transfer/disturbance
 Forward/backward (sideways)
oscillation
 Only occurs in mechanical waves
 Pressure variations based on that of
the mean position
 Sound
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Important terms in describing waves 
1. Mean position: the center where the disturbance originates – an undisturbed point (also
called an equilibrium point). Every particle has a mean position that it oscillates about.
2. Displacement: shortest distance of the oscillating particle from the mean position measured
at a certain point in time.
3. Time period: time taken to complete one oscillation (s).
4. Amplitude: maximum displacement of a particle from its mean position. Amplitude ∝
energy level of the wave.
5. Crest: the position of maximum positive displacement of a wave.
6. Trough: the position of maximum negative displacement of a wave.
7. Compression: a region of a longitudinal wave wherein the particles of the medium move
closer together thus creating maximum pressure and displacement from the mean position
(also maximum density). The distance of the center of compression from the mean position
is the crest.
8. Rarefaction: a region of a longitudinal wave wherein the particles of the medium move
further apart thus creating minimum pressure and displacement from the mean position
(also minimum density). The distance of the center of rarefaction from the mean position is
the trough.
9. Wavelength: the distance traveled by the wave during one time period. The distance
between two successive crests/troughs. Wavelength varies with density of the medium.
10. Frequency: number of complete waves/oscillations per second – does not change with
density of the medium.
11. Speed of the wave: proportional to wavelength.
12. Wavefront: a line joining successive crests/troughs/same points on a wave.
Frequency (Hz) =
1
Time Period (s)
OR f =
1
t
Speed of the wave (m/s) = Wavelength (m) × Frequency (Hz) OR V = λf
Wave effects 
1. Reflection: the wave is reflected from a vertical surface at the same angle as it strikes it
2. Refraction: occurs when the density of a medium changes thus changing the speed of the
wave and making it change direction – frequency remains constant
3. Diffraction: the waves bend around the sides of an obstacle or spread out while passing
through a gap (gaps wider than the wavelength produce less diffraction)
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Sound 
Sound waves are mechanical and longitudinal waves caused by vibration in a medium (can be solid,
liquid or gas – sound cannot travel through a vacuum)
Speed of sound:




In dry air at 0°C = 330 m/s
In dry air at 30°C = 350 m/s
Pure water at 0°C = 1400 m/s
Concrete = 5000m/s
Refraction of sound = Since sound travels slower at cooler temperatures closer to the ground and
faster at higher temperatures (occurs at night), waves bend towards the ground as a result of the
change in speed
Reflection of sound = Hard surfaces reflect sound waves in the form of echoes.
Speed of sound =
2 × Distance to the surface
Time taken for the echo to be heard
***Used to measure distances and depths since speed is already known
Frequency α Pitch of sound = Humans can detect sounds from a frequency of 20 Hz to 20,000 Hz.
Sounds higher than this range are called ultrasonic.
Amplitude α Loudness of sound (decibels)
Quality of sound = when sounds have the same fundamental frequency mixed in with different
weaker frequencies called overtones, they have differing qualities.
20
Light 
— A form of radiation (spreads out from its source) that travels in straight lines
— Travels as an electromagnetic wave; can travel through a vacuum
— Speed of light in a vacuum = 3 × 108 m/s
Properties: 1. Reflection 
Only occurs when the light ray cannot pass through the surface
 Ray striking the surface = incident ray
 Ray leaving the surface = reflected ray
 Line perpendicular to the surface = normal
 Angle that the incident ray makes with the normal = angle of incidence
 Angle that the reflected ray makes with the normal = angle of reflection
 Angle of incidence = angle of reflection
Regular reflection
Diffused reflection
Reflection of rays on a smooth plane surface –
Reflection on an irregular surface – rays are
all incident rays have parallel reflected rays
reflected in different directions
Forms an image on the surface
Doesn’t form an image
Image formed in a plane mirror:
— The same size as the object
— Upright and laterally inverted
— Virtual
— As far behind the mirror as the object is in front
— A line joining equivalent points on the object and the image passes through the
mirror at right angles
2. Refraction 
Refers to the bending of light when it passes through a medium of different density due to the
change in its speed
Angle of refraction = the angle that the refracted ray makes with the normal
Snell’s Law:
When light is refracted from a rarer to a denser medium, an increase in the angle of incidence
sin i
(i) produces an increase in the angle of refraction (r):
= constant = refractive index
sin r
Refractive index is also =
Speed of light in vacuum
Speed of light in the denser medium
21
Situations of refraction:
a. When light travels from a rarer to a denser medium
 Ray is refracted towards the normal
 Speed decreases
 Angle of incidence > angle of refraction
 Total internal reflection can occur: — Critical angle = the angle of incidence in the denser medium for which its angle
of refraction into the rarer medium is 90° = sin-1
1
refractive index
— Total internal reflection is when light travels from a denser medium to a rarer
medium and the angle of incidence is greater than the critical angle, there is no
refracted ray since all the light is reflected back into the denser medium
b. When light travels from a denser to a rarer medium
 Light is refracted away from the normal
 Speed increases
 Angle of incidence < angle of refraction
c. When light enters a medium perpendicular to its surface
 Light ray does not bend
 Speed changes according to the difference in density of the medium
 Angle of incidence = angle of refraction = 90°
Lenses 
a) Concave lenses: thicker around the edges than at the center – light rays are diverged (bent
outwards)
b) Convex lenses: thicker at the center than at the edges – light rays are converged to a single
point after passing through
Drawing ray diagrams 
 The point where the rays converge is called the principal focus
 The distance of the principal focus from the center of the lens is called the focal
length
 The line joining the principal focus to the center is the principal axis
 A ray needs to be drawn joining a point on the object through the center of the
lens
 Another ray from the object running parallel to the principal axis passes through
the focus after leaving the lens
 The intersection of these two rays forms a point on the image
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 If an object is closer to the lens than the focus, it will form a virtual, upright
image (normally magnified) because it cannot be formed on a screen (no rays
meet to form it)
 If an object is further from the lens than the focus, it will form a real, inverted
image (normally diminished) because it can be formed on a screen (rays meet to
form it)
Height of the image
 Linear magnification = Height of the object
Correcting defects in vision 
a) Short sight: the lens cannot be made thin enough to look at distant objects. As a result of
excessive bending of light the rays converge before reaching the retina. Concave lenses are
used to correct this.
b) Long sight: the lens cannot be made thick enough to look at close objects. As a result of
insufficient bending of light the rays do not meet by the time they reach the retina. Convex
lenses are used to correct this.
23
TOPIC 8: ELECTRICITY 
Static Electricity 







There are two types of electric charges; positive and negative
Like charges repel, unlike charges attract
The closer the charges are, the greater the electric forces acting between them
Electric field lines denote the path taken by a test positive charge – since they denote the net
effective charge, electric field lines can never intersect
Charge of one electron = − 1.6 × 10-19 C
Charge of one proton = 1.6 × 10-19 C
Electric field lines: Isolated charges
Charged plates
Static electric charges



An object becomes negatively charged when it gains electrons and positively charged when in
loses electrons
Static charges can be acquired through friction or earthing
Electrostatic induction occurs when a conductor becomes charged when a charged body is
brought near but not in direct contact with it
Conductors and insulators:
a) Conductors allow electrons to pass through them. Metals are good electrical conductors
due to the presence of free, mobile electrons – they lose charge almost immediately.
b) Insulators contain tightly bound electrons that are not free to move. Non-metals and
plastics are good insulators – they can accumulate charge without losing it to the
surroundings.
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c) Semiconductors are poor conductors when cold but good conductors when warm.
Examples are silicon and germanium.
Electrical Circuits 
Quantity
Abbreviation
Current
I
Charge
Q
Time
t
Voltage
V
Energy
Power
E
P
Resistance
R
Unit
Definition
The amount of charge flowing through a
Ampere (A)
circuit per unit time (travels from positive to
negative)
The quantity of unbalanced positive or
Coulomb (C)
negative electricity in a body
Seconds (s)
An electromotive force (the energy required to
push one unit of charge through a circuit) or
Volts (V)
the potential difference (work done in moving
one unit charge through the circuit
component).
Joules (J)
J/s or Watts (W) Rate at which a substance transforms energy
The degree to which a material opposes the
Ohms (Ω)
passage of an electric current
Formulae 
1.
2.
3.
4.
V = IR (Ohm’s Law)
E = QV = I × t × V
Q=I×t
W = IV
5. R = 𝜌 ×
Length (m)
Cross sectional area (m2 )
where rho or 𝜌 is the specific resistivity constant (given that the
temperature is constant) that varies with the material used
∴
R1
R2
A L
= A1 L1 (for the same material)
2 2
6. P = VI
7. P = I2R
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Series and parallel circuits 
Series circuits
If one component is removed or disconnected,
all the others stop working because the circuit is
broken
Each component shares the voltage from the
battery
Total voltage = sum of the potential difference
across each component
The current through each component is the
same
Overall circuit resistance increases with the
number of resistors
Total resistance = sum of resistance across each
individual resistor
R = R1 + R2 + …
Parallel circuits
If one component is removed, the others still
function because they are connected by an
unbroken circuit
Each component gets the full voltage from the
battery because each is connected directly to it
Voltage through each component is the same
Total current = sum of the currents in the
branches
If two or more resistors are connected in
parallel they give a lower resistance than that of
any individual resistor
1
R
R
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=
1
+
1
+…
R1
R2
R1 × R2
= R + R (for two resistors)
1
2
Symbols used to depict Electrical Circuit Components 
Component
Circuit Symbol
Cell
Battery
Direct Current supply
Alternating Current supply
Fuse
Earth (Ground)
Lamp (indicator)
Inductor (Coil, Solenoid)
Switch
Resistor
Variable Resistor (Rheostat)
Voltmeter
Ammeter
Connecting wire
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TOPIC 8: MAGNETISM 
Properties of magnets:
 A magnet has a north pole and a south pole
 Law of magnetic poles = like poles repel, unlike poles attract (repulsion occurs only when both
poles are magnets)
 The magnetic field is strongest at the two poles
 Only magnetic materials (iron, nickel, cobalt) are attracted by magnets
 Magnetic field lines –
Bar Magnet
Repulsion
Attraction
Induced magnetism:
 A permanent magnet can temporarily pass its magnetism to a magnetic material
 When a magnetic material is placed near to or in contact with a permanent magnet, its poles
align themselves, inducing magnetism in it
 Soft magnetic materials are magnetized faster, but retain magnetic properties for less time –
E.g. Iron
 Hard magnetic materials take longer to be magnetized, but retain their magnetism for longer
– E.g. Steel
Methods of magnetization:
 Magnetization by stroking – the magnetic material can be stroked several times by the poles
of permanent magnets. Using two magnets (double/divided touch) is faster than using one
(single touch).
 Electrical method – placing the material inside a solenoid and connecting it to a direct current
thus exposing it to the strong magnetic field created by an electromagnet.
Methods of demagnetization:
 Heating and hammering – this causes the magnetic poles’ alignment to become irregular
again.
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 Electrical method – placing the magnet inside a solenoid and connecting it to an alternating
current.
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GENERAL: IMPORTANT POINTS AND COMMON MISTAKES 
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During circular motion, even though the speed does not change, there is a constant
change in direction therefore change in velocity. This mean that the object is
CONSTANTLY ACCELERATING – there is a centripetal acceleration towards the center of
the force
In a velocity/time graph, if an object travels up and then back down in a straight line
(e.g. a ball thrown upwards) one direction will be shown as positive while the other will
be shown as negative [the line will extend below the x-axis]
While parachuting, at first the person is free falling towards the ground at a constant
acceleration (10 m/s2). The air resistance balances the acceleration and the object
reaches terminal velocity. When the parachute is opened, air resistance increases
greatly, slowing the person down. The gravity then balances the increased air
resistance and the person reaches a slower terminal velocity. There is no further
acceleration until the person reaches the ground.
When any question on force is asked, don’t forget to mention direction since force is a
vector and is meaningless without direction.
ALWAYS MENTION UNITS UNLESS THE QUESTION HAS WRITTEN UNITS IN THE BLANK
ALWAYS LABEL DIAGRAMS AND USE ARROWS FOR FORCES
WHEN SHOWING WEIGHT, ALWAYS DRAW THE LINE FROM THE CENTRE OF MASS
DURING ANY MEASUREMENT QUESTIONS – READ THE SCALE
When a fairly ELASTIC object is dropped – at the beginning, it will have zero speed, and
then it accelerates constantly towards the ground (free fall). Air resistance slows it
down until it reaches a terminal velocity. The object maintains the same speed until it
hits the ground. It DOES NOT LOSE ITS ENERGY WHEN IT TOUCHES THE GROUND AT
FIRST. The energy still remaining causes it to be compressed, after which its speed
becomes zero, and then it rebounds with a lower maximum height than previously.
In measurement diagrams, ALWAYS ALIGN THE ZERO MARK WITH THE EYE LEVEL.
When asked for the OVERALL change in velocity, it is always FINAL – INITIAL
Latent heat of FUSION is ALWAYS LESS than that of VAPORIZATION
Gravitational potential energy is always calculated using the VERTICAL DISTANCE
moved by the object
When calibrating a thermometer, it should be either placed JUST ABOVE boiling water
or inside PURE boiling water. Not in boiling water – since the water’s purity here is not
specified.
Impurities increase boiling point and decrease melting point – some impure substances
can also boil over a range of temperatures
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Gases have the most potential energy and solids have very little. Specific heat capacity
in gases is higher due to this.
When changing in state, there is NO CHANGE IN KINETIC ENERGY, only
INTERMOLECULAR SPACING CHANGES.
When the question asks to define - pay attention to whether it is SPECIFIC heat
capacity or just HEAT CAPACITY and define accordingly
When drawing Brownian motion – MAKE ARROWS
Pay attention to the axis titles in distance/time/speed graphs
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