This document provides information on various physics concepts related to length, time, motion, forces, energy, and thermal properties. It defines key terms such as speed, velocity, acceleration, density, mass, weight, pressure, states of matter, temperature, thermal expansion, and specific heat capacity. Measurement techniques are described for length, time, density, forces as well as thermometers. Relationships between various variables are defined through equations and experiments. Overall, the document serves as a review of basic physics topics.

1. Length and time
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

2. LENGTH MEASUREMENT
- Ruler
- Vernier caliper

3. LENGTH MEASUREMENT
- Micrometer screw gauge

4. VOLUME MEASUREMENT
- Measuring cylinder
36.5 cm3

5. TIME MEASUREMENT
- Analogue watch
- Digital stop watch

6. OBTAINING AVERAGES
- Rather than measuring the thickness of a single sheet of paper, it is more accurate
to measure the thickness of 1000 sheets of paper and calculate the average:
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑠𝑖𝑛𝑔𝑙𝑒 𝑠ℎ𝑒𝑒𝑡 =
𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 1000 𝑠ℎ𝑒𝑒𝑡𝑠
1000
- Rather than to calculate the time taken for a single pendulum swing, it is more
accurate to measure the time taken from 100 swings and average the results:
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑡𝑖𝑚𝑒 𝑓𝑜𝑟 𝑠𝑖𝑛𝑔𝑙𝑒 𝑠𝑤𝑖𝑛𝑔 =
𝑇𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 𝑓𝑜𝑟 100 𝑠𝑤𝑖𝑛𝑔𝑠
100

7. Motion
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

8. Speed and velocity
- Speed is the change in distance per second
- Velocity is the change in displacement per second
Speed = 1000m / 2000s = 0.5m/s
Velocity = 0 / 2000 = 0 m/s

9. Acceleration
- Acceleration is the change in velocity per second (ms-2)
- Positive acceleration is when an object increases velocity over time
- Negative acceleration is when an object decreases velocity over time (deceleration)

10. Free fall
- Any object close to the earth’s surface will be pulled by the earth’s gravity (Fg)
- Gravity causes objects to free fall at a constant acceleration of 9.8ms-2
- Air resistance opposes gravity
- Eventually the downward force of gravity and the upward force of air
resistance will be the same
- Object will stop accelerating, and fall at a constant velocity (terminal velocity)

11. Distance-time graphs
- Distance time graphs plot distance
travelled against time
- Speed of travel can be calculated via
the gradient of the graph
Speed of travel between 0-6s
- The change in X axis = 10m
- The change in Y axis = 6s
- Gradient (speed) = 10/6 = 1.67 m/s

12. Speed-time graphs
- A speed-time graphs plots speed against time
- Distance traveled can be calculated via the area
underneath the graph
- Acceleration can be calculated by the gradient on the
graph

13. Mass and weight
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

14. Mass
- The amount of matter that makes up an object
- Measured in kilograms (Kg)
- All masses have inertia (resistance to change in motion)
- The larger the mass, the larger the inertia

15. Weight
- Force on a mass due to gravity
- Measured in newtons (N)
g (10ms-2), m (Kg), W (N)

16. Density
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

17. Density formula
Or kg/m3) = mass (kg) / volume
(m3)

18. Density measurement – Liquid
- Put measuring cylinder on weighing scale and reset to
zero
- Pour liquid into measuring cylinder and measure volume
- Measure weight of liquid by reading off the weighing
scale
- Calculate density via mass / volume
??? KG

19. Density measurement – regular solid
- Measure dimensions of solid (height/width/length)
- Calculate volume of solid (height X width X length)
- Measure mass of solid with weighing scale
- Density = mass / volume
??? KG
height

20. Density measurement – Irregular solid
- Measure weight of solid via weighing scale
- Add water into measuring cylinder and measure initial volume
- Submerge solid into the water
- Measure the final volume of water in the cylinder
- Volume of solid = final volume – initial volume
- Density = mass / volume
Initial volume
??? KG
Final volume

21. Flotation / buoyancy
- Object will float if it is less dense than the liquid it is placed in
- Object will sink if it is more dense than the liquid it is placed in

22. Forces
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GENERAL PHYSICS

23. What are forces?
- A force is a push or pull that causes a change in speed, direction, or shape of an
object

24. Effects of forces on a spring
- When a load is hung off a spring, it causes a downward force on the
spring
- The amount of extension will depend on the amount of force
- EXPERIMENT:
1. Measure original position of spring without any mass (L0)
2. Add 100g mass and measure the position of spring again (L1)
3. Calculate extension I.e. change in length L1 – L0
4. Then add another 100g mass (total=200g) and measure new length (L2)
5. calculate extension L2 – L0
6. Repeat the process until a total of 600g mass is added

25. Effects of forces on a spring
Mass (kg) Force (N) Length (cm) Extension
0 0 10 0
100 1000 20 10
200 2000 31 11
300 3000 41 10
400 4000 52 11
500 5000 60 8
600 6000 60 0

26. Extension load graph
- Hooke’s law: Extension directly proportional to
force applied until the limit of proportionality
reached
- Further force causes non-proportional extension,
but original shape is still restored after removal of
force
- After elastic limit, the original shape of the spring
is not restored even after the removal of force
- If force applied is too great, the spring may break

27. Force  Acceleration
- A net force on an object will cause acceleration
- Forces are vector quantities, and therefore act in a specific
direction
- The resultant force is the overall force when the size and
direction of all forces acting are taken into account
- Forces in the same direction are added
- Forces in opposite directions are subtracted

28. Centripetal force
- Centripetal force is the force that causes an object
to move in a circle
- The force always acts at a right angle to the
direction of movement of object
- Force constantly changes the direction of the
object without changing the speed
- Since velocity is a vector quantity, the velocity is
changing, and therefore the object is accelerating
- Centripetal force increases if:
1. The mass of the object increases
2. The speed of the object increases
3. The radius of the circle decreases

29. Friction and air resistance
- Friction is a force between two surfaces which impedes motion and results in
heating
- It is the resistance that one object encounters when moving over another object
- Air resistance is a form of friction
- Air molecules will collide against free falling objects in the air, creating an upwards
force which opposes the downward force of gravity

30. Moments (turning effect)
- The moment of a force about a pivot is equal to force multiplied by the perpendicular
distance from the pivot
- When the clockwise moment > anticlockwise moment, the resultant moment = clockwise
- When the anticlockwise moment > clockwise moment, the resultant moment =
anticlockwise
- An object is in equilibrium if there is no resultant moment i.e. clockwise moment =
anticlockwise moment

31. Examples

32. Centre of mass
- Centre of mass is the point on an object where the
overall mass can be considered to be concentrated, and
hence where the weight of the object is considered to act
- The center of mass of a plane lamina can be determined
with a simple experiment
1. Push pin through point anywhere on edge of lamina
2. Allow lamina to swing and eventually hang still
3. Mark a vertical line dowards
4. Take out pin and push through a second point
5. Again, let the lamina settle and mark a second vertical
line
6. The point of intersection between two lines = center of
mass

33. Stability
- The stability of an object is determined by its center of mass
- An object is stable if its weight (the force acting on center of mass) is inside the base
of the object
- An object will tip over if the weight falls outside the base of the object

34. Vectors and scalars
- Vector quantities have magnitude and direction
- Scalar quantities have magnitude only
- The resultant vector of two vector quantities can be calculated via scale diagrams
WHAT IS THE RESULTANT VECTOR???

35. Scale diagrams
1. Choose a scale to draw on paper i.e. 1N = 1cm
2. Re-draw the diagram on paper with appropriate lengths and angles
3. Arrange forces nose-to-tail
4. Draw the resultant force in the direction of the arrows, and measure the length
5. Revert units back from cm into N i.e. 12cm = 12N

36. Momentum
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

37. Momentum and impulse
- Moment is mass in motion, and any moving object will have momentum
- A change moment is impulse
- Momentum is always conserved
- Consider a collision between object 1 and object 2
- Total momentum before collision = total momentum after collision

38. Energy, work and power
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

39. Energy
- Energy is always conserved
- Energy is never created or destroyed, it is only
transferred or transformed from one form to
another
EXAMPLES
1. Light bulb: Electrical energy  Heat + light
2. Water fall: Gravitational  Kinetic
3. Battery: Chemical  Electrical

40. Kinetic and gravitational potential energy
- Kinetic energy
-Gravitational potential energy

41. Energy resources

42. Energy, work and power
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

43. Energy
- Energy is always conserved
- It is never created or destroyed
- Rather, energy is transferred or
transformed from one form to another.

44. Conservation of energy
- In a light bulb, electrical energy is transformed into heat energy and light energy
- In a water fall, gravitational energy is transformed into kinetic energy
- In a battery, chemical energy is transformed into electrical energy

45. Kinetic energy
- Energy of a moving object
Answer = C

46. Gravitational potential energy
Answer = A

47. Energy resources

48. Pressure
CAMBRIDGE IN 5 MINUTES
GENERAL PHYSICS

49. Pressure
- Pressure is the force exerted per unit area

50. Mercury barometer
- Pressure beneath liquid surface (at
base of mercury column) can be
calculated

51. Manometer

52. Simple kinetic molecular
model
CAMBRIDGE IN 5 MINUTES
THERMAL PHYSICS

53. States of matter
- Matter is any substance that occupies physical space.
- The kinetic theory of matter sates that matter is made of tiny particles in constant
motion

54. States of matter

55. Temperature
- Temperature is the average kinetic energy of particles within a substance
- Heating a substance causes particles to move quicker, therefore increasing their
kinetic energies, and hence increasing the temperature
- Heating can change the state of matter of a substance:

56. Brownian motion
- One day, a scientist was observing a pollen grain suspended in water.
- He realized that the pollen grain was actually moving in random motion
- Brownian motion is the random movement of particles in a fluid due to bombardment
of molecules of the fluid itself

57. Pressure of a gas
- Pressure of a gas is defined as a change of momentum of particles striking the walls
of the container, exerting force

58. Pressure of a gas
-Higher temperature (at constant volume)  Stronger collisions against container wall
 Exerts more force on container wall  Increases pressure
- Lower volume (at constant temperature)  Stronger & more frequent collisions
against container wall  Exerts more force on container wall  Increases pressure
Boyle’s law states that for a fixed mass of gas at a
constant temperature, the volume is inversely proportional
to the applied pressure

59. Evaporation
- Evaporation is the change from liquid to gas below the boiling
point
- Not all particles in a liquid have the same kinetic energy
- Some particles may be moving quicker (higher energy), and
some may be moving slower (lower energy)
- Remember: the AVERAGE kinetic energy = temperature
- Particles with a large amount of kinetic energy may overcome
attractive forces and escape the surface of the liquid as a gas
- Since most energetic particles escape, it will lower the
temperature (average kinetic energy) of the liquid
- Factors that cause increased evaporation
1. Higher temperature
2. Larger surface area
3. More air flow over surface of the liquid

60. Thermal properties &
temperature
CAMBRIDGE IN 5 MINUTES
THERMAL PHYSICS

61. Thermal expansion
- Solids, liquids, and gases expand when heating
- This is because particles gain more kinetic energy when heated, and therefore gain
more separation from neighboring particles
- The extent of expansion varies:
1. Solids expand the least
2. Liquids expand more than solids
3. Gases expand more than liquids

62. Thermal expansion of solids
- Railway tracks have a small gap to account for thermal expansion
- If there were no gaps, the expansion would cause misalignment problems
The rails in the above image are the result of the thermal
expansion and lack of gap between the adjacent rails.
These gaps give room for expansion during hot weather

63. Thermal expansion of a liquid
- Thermal expansion of liquids are used in liquid-in-glass thermometers
- When thermometer placed in hot liquid, the alcohol or mercury expands
- This forces the liquid to move up the narrow tube

64. Thermal expansion of a gas
- When temperature of a gas is increased, particles gain more kinetic energy
- This means the gas will take up more space (volume) if allowed

65. Measurement of temperature
1. Physical property that varies
with temperature
-Thermal expansion
-Electrical resistance
-Potential difference
2. Two fixed points
3. Scale

66. Measurement of temperature: Fixed points
- To define a temperature scale, two reference temperatures called fixed points must
be used
- These are temperatures at which certain particular physical properties manifest
themselves i.e. freezing/boiling
- Celsius scale is defined by freezing point of water (0) and boiling point of water (100)

67. Types of thermometers
Liquid-in-glass thermometers
- Liquid expansion
- Convenient to carry
- Limited range of temperatures 0-100
- Delayed temperature reading
Thermocouple
- Voltage differences
- Large range and accuracy
- Instant temperature readings

68. Thermal definitions
Internal energy
• Energy contained within the system
• If an object is heated, since the particles gain more kinetic energy, the internal energy is increased
Thermal capacity
• Amount of energy required to change the temperature of an object by one unit (1°C)
• Thermal capacity is dependent on the material and mass of the object
Specific heat capacity
• Amount of energy needed to raise the temperature of an object per unit mass
• In other words, the energy required to raise the temperature of 1Kg of that material by 1°C

69. Specific heat capacity of water
We need:
- Mass of substance (m)
- Temperature change of substance (ΔT)
- Energy used to cause this temperature
change (E)

70. Specific heat capacity of water
- 0.50 kg water is used into a container with
insulation
- A thermometer is used to measure the
temperature of the water
- An electrical heater with known power (50 W) is
placed in the water
- Initial temperature reading is taken
- The heater is switched on and a timer is started
simultaneously
- Timer is stopped when the temperature rises by
10°C

71. Specific heat capacity of water
Energy supplied by heater (E) = power X time = 50W X 420s = 21 000J
Mass of water (m) = 0.50 kg
Change in temperature (ΔT) = 10°C
C = 4200 J/(Kg°C)
In reality a lot of energy from the heater would not be transferred 100% to the water, so the
value would be a bit different from 4200.

72. The concept of melting
- Solid  Liquid
- As solid is heated, temperature rises
until MP is met
- Once MP reached, solid will transition
into a liquid
- During transition phase, temperature is
constant
- Once solid has fully melted,
temperature of liquid rises again
- Latent heat of fusion is the energy
required to melt a solid at melting point

73. Concept of boiling
- Liquid  Gas
- As liquid heated, temperature of liquid rises until
BP is met
- Once BP reached, temperature stays constant as
liquid becomes a gas
- Once liquid has fully boiled into gas, temperature
of the gas begins to rise
- Latent heat of vaporization is the energy required
to vapourize a liquid at boiling point

74. Boiling vs evaporation
- Boiling and evaporation is a change in state from liquid  Solid
- Differences:
- Boiling occurs at a fixed temperature
- Evaporation can occur at all temperatures, including below the boiling point
- Evaporation decreases the temperature of the remaining liquid.
- During boiling the temperature remains constant.

75. Specific latent heat
- Specific latent heat of fusion
- Energy required to melt 1kg of solid at its melting point with no change in
temperature
- Specific latent heat of vapourization
- Energy required to vapourize 1kg of liquid at boilting point with no change in
temperature

76. Specific latent heat of fusion of ice
- Fill a funnel with ice and place a beaker beneath it
- Place a 50W heater in the ice
- Turn on the heater & start the timer immediately
- After 10 minutes turn off the heater
- Measure the mass of the accumulated water in the beaker
•Energy supplied (E) = power X time = 50 X 600 = 30
000J
•Δm = 0.1L
•L = 30 000 / 0.1
= 300 000J/Kg
Lets assume that we accumulated a total of 0.1L of water
in 10 minutes (600 seconds)

77. Specific latent heat of vaporization of
water
- Part fill a beaker with boiling water and place on a balance
- Place a 50W heater in the water
- Switch the heater and wait for water to boil
- Once water is boiling start the timer and take the balance reading
- When the mass reading has decreased by 0.1 kg, stop the timer
•Energy supplied (E) = power X time = 50 X 4600 = 230
000
•Δm = 0.1L
•L = 230 000 / 0.1 = 2 300 000 J/Kg
Lets assume it took 4600 seconds to reduce the mass by
0.1Kg

78. Thermal processes
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THERMAL PHYSICS

79. Conduction –Good conductors
- Conduction is the process by which heat or electricity is directly transmitted through the material of a substance
- Occurs via molecular vibrations (transfer of kinetic energy through the structure)
- Metals are good conductors because of their structures:
- When one end of metal is heated, particles gain kinetic energy and vibrate quicker
- This causes neighboring particles to vibrate quicker and results in a domino effect across the structure
- Through the transfer of kinetic energy in the form of vibrations, heat is transferred from one end to the other
- Free electrons are highly mobile and rapidly quickens the transmission of energy

80. Metal conduction experiment
- Demonstration of copper being a good
conductor
- As copper bar is heated, the drawing pins
will fall off one (from the one closest to the
heat)
- This is because the metal conducts heat from
the hot end to the cold end
- Heat melts the wax and therefore drops the
pins

81. Conduction - Poor conductors
- Insulators are very poor conductors such as rubber
- Absence of free electrons makes the passage of vibrations/kinetic energy very
difficult
- Water is a poor conductor
- As the water at the top of boiling tube is heated, it
eventually boils
- However, the ice at the bottom does not melt
- Heat therefore does not reach the bottom of the tube

82. Convection
- Convection is a method of heat transfer strictly in liquids and gases

83. Radiation – Emission experiment
- Infra-red radiation is part of the electromagnetic spectrum , and is emitted by any hot object
- Infra-red can be emitted, absorbed, or reflected
- Different types of surfaces can affect the emission and absorption of infra-red radiation
Set-up & procedure
•A metal cube with is painted with 4 different types of
surfaces: matt black, shiny black, white and silver
•The cube is filled with boiling water
•A heat detector is placed at a constant distance
away from the cube i.e. 50cm
•The cube is rotated so that each side faces the heat
detector in turn, and the readings are noted
Results (in order of emission levels)
•Matt black (highest) -> Shiny black -> White -> Silver
(lowest)

84. Radiation – Absorption experiment
Set-up & procedure
•A radiant heater is placed in the middle of two plates at equal
distance away from the heater
•One plate is matt black and the other is silver
•A thermometer is placed on each plate and initial reads of the
thermometers are recorded
•The heater is switched on and the temperatures of each of the
plates are measured in equal intervals
Results:
•The temperature of the matt black plate will increase quicker
than the silver
•Matt black surfaces are therefore better absorbers of radiation

85. Wave properties
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WAVES, LIGHT, SOUND

86. Waves
- Waves transfer energy from one place to another without the transfer of particles
themselves in the medium
- Particles vibrate in fixed positions

87. Types of waves
- Longitudinal waves
- Particles vibrate parallel to direction of
wave
- Compressions (particles closest together)
and rarefactions (particles furthest apart)
- sound is longitudinal
- Transverse waves
- Particles vibrate perpendicular to wave
direction
- Peaks (particles highest from rest position)
and troughs (particles lowest from rest
position)

88. Important definitions
Wavelength is the distance between adjacent particles
that are at the same point in their vibration
In a transverse wave, it is the distance between two
adjacent peaks or troughs
In a longitudinal wave, it is the distance between two
adjacent compressions or rarefactions
Amplitude is the maximum displacement of particles
from rest position
In transverse waves, it is the distance between the
rest position to the peak
Velocity of the wave is the distance traveled per second,
and is measured in m/s
Frequency of the wave is the number of complete waves
passing a point per second, and is measured in hertz
(Hz)
Wavefronts are the locations of all particles of the
medium in the same state of vibration. It is
perpendicular to wave direction. The distance between
one wavefront to the next is the wavelength

89. Reflection, refraction and diffraction
REFLECTION
- When waves hit a plane surface, it will become reflected
- The frequency/speed/wavelength stays the same
- Using a ripple tank can demonstrate this

90. Reflection, refraction and diffraction
REFRACTION
- Speed of light changes when a wave travels from one medium to another medium
with a different density
- This causes the direction of the wave to change
- Water travels more slowly in shallow water compared to deep water:

91. Reflection, refraction and diffraction
DIFFRACTION
- Waves spread out when passing through a narrow gap or across the edge of an object
- As water passes the gap, it spreads out as follows:
- Extent of diffraction depends on size of gap compared to
wavelength
- Diffraction can also occur at edge of barrier
- Longer wavelength = greater diffraction

92. Light
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WAVES, LIGHT, SOUND

93. Reflection of light
- Incident ray, reflected ray, and the normal are all on the
same plane
- Angles of incidence and reflection are measured in
relation to the normal
- Angle of incidence = angle of reflection

94. Mirror reflection
- Mirrors reflect light coming from objects
which then enter our eyes
- Ray diagrams can demonstrate how an image
of an object is formed inside the mirror:
1. Trace 2 incident rays from object
2. Trace the reflected rays (remember: angle
of incident = angle of reflection)
3. Trace back the rays into the mirror
4. The point of intersection between two rays
behind the mirror is where the image is
formed

95. Properties of mirror images
- Mirror images are virtual images
Virtual images are formed when light APPEARS to converge in a location which
forms an image
Real images are formed when light ACTUALLY convergences in a location which
forms an image
- Same size as the actual object
- Same distance away from the mirror as the actual object
- Laterally inverted

96. Real vs virtual image

97. Refraction of light
- Light travels at different speeds depending on the refractive index of the material
- Every material (medium) has a different refractive index
The higher the refractive index, the slower light travels
The lower the refractive index, the faster light travels
- Generally the denser the material the higher the refractive index

98. Refraction of light through mediums
- Consider light travelling from A to B
- There are two possible scenarios:
1. Refractive index of A is lower than refractive index of
B
2. Refractive index of A is higher than refractive index of
B
- Consider light going from air into glass, and then going
back out the other end
- Air has a lower refractive index than glass
- When light enters, it travels from low to high index
- When light leaves, it travels from high to low index
•i = angle of incidence
•r = angle of refraction
•Light slows down as it enters a higher index material,
therefore bends towards the normal
•Light speeds up as it enters a lower index material,
therefore bends away from the normal

99. The critical angle & total internal reflection
- Consider light rays going from a medium of higher to
lower index
- Light bends away from the normal
- As angle of incidence increases, angle of refraction
increases as well
- If the angle of refraction is larger than 90, that means
that the entire light is reflected back into the medium (total
internal reflection)
- The critical angle is this limit – it is the angle of incidence
that causes an angle of refraction of 90
- When the angle of incidence is larger than the critical
angle, then we get total internal reflection

100. Total internal reflection in optical fibres
- Total internal reflection is used in optical fibres
- Optical fibre has a thin glass core with a outer
cladding with a lower refractive index
- Total internal reflection occurs for all rays that hit
the boundary between core and cladding at a angle
larger than the critical angle

101. Thin converging lens
- Light coming from a very distance
object are considered parallel rays
- When parallel rays pass a convex
(converging) lens, light rays are focused
at a single point called the principle
focus
- The imaginary horizontal line at right
angles to the lens is the principle axis
- The distance from the lens center to
the principle focus is the focal length

102. Ray diagrams
- Light travels from an object, passes through a convex lens,
and forms an image
- It is your job to trace the light rays and determine the size
and position of the image
- All convex lenses will have a focal point (or principle focus)
The focal point and focal length is the same on either
side of the lens
- The initial construction will look like this:
- Consider an object being placed on the left hand side
- There are three position positions for the object
1. 2F and beyond
2. Between 2F and F
3. between F and the lens
- The resulting image of the object will be different depending
on these positions!

103. Ray tracing: Object beyond 2F
- From the top of the object, draw three rays as
shown
- The point at which these three lines meet is
where the imagine is positioned
- This results in an image that is real, inverted,
and diminished

104. Ray tracing: Between 2F and F
- From the top of the object, draw three rays as
shown
- This results in an image that is real, inverted,
and magnified

105. Ray tracing: Between F and the lens
- The image is virtual, upright and magnified

106. White light and dispersion
- White light is a complex combination of all of the different
wavelengths of the visible spectrum
- Each of the wavelengths have a different colour i.e. green
has a wavelength of 500nm and red has a wavelength of
700nm
- Light of a single frequency is called monochromatic light
- Combining all monochromatic light results in ‘white light’
- We can separate out the different wavelengths by using a
prism
- This is called dispersion

107. Electromagnetic spectrum
CAMBRIDGE IN 5 MINUTES
WAVES, LIGHT, SOUND

108. Summary of electromagnetic spectrum
-All electromagnetic waves can travel through
vacuum and all travel at the speed of 3 X 10 ^ 8
m/s in vacuum
- The higher the frequency, the higher the energy
of radiation

109. Sound
CAMBRIDGE IN 5 MINUTES
WAVES, LIGHT, SOUND

110. Production of sound
- Sound is a result of vibrating objects that cause a vibration of air
molecules
- Sound is a longitudinal wave (with compressions and rarefactions)
- We hear sound when sound waves reach our ear which causes
vibrations in our ear drums
- We hear frequencies of 20 Hz to 20KHz
- All waves (including sound) have a frequency and amplitude
1. Frequency (Hz) is the number of waves that passes a
fixed point her second
The higher the frequency the higher the pitch
2. The amplitude of the wave is the maximum
displacement of the vibration particles
The larger the amplitude, the louder the sound

111. Speed of sound
- Sound cannot travel through vacuum
- Sound must be transmitted through vibrations of particles within a medium
- The closer the particles are within the medium, the faster sound will travel
AIR = 330 m/s
WATER = 1500 m/s
METALS = 5000 m/s
- Air particles are very spread out, so sound does not travel very fast
- Metals on the other hand are usually solids, and particles are much closer together allowing quicker
transmission of sound waves

112. Determining of speed of sound in air
- Speed of sound in air is approximately 330 m/s
- We can experimentally proves this by using this set up:
1. Two microphones are separated by exactly 1m
2. They are connected to a digital timer that starts when it gets signal from mic 1 and stops when it gets a signal from
mic 2
3. A hammer is used to hit a metal block to make sound
- The timer will record to travel between mic 1 to mic 2 the time taken from sound (i.e. 0.003 seconds)
- Since speed = distance / time
1m / 0.003 = 330 m/s

113. Echoes
- When sound waves get reflected off a surface, it generates an echo

114. Simple phenomena of
magnetism
CAMBRIDGE IN 5 MINUTES
ELECTRICITY & MAGNETISM

115. MAGNETISM
• All magnets are made of ferromagnetic material (mainly iron/steel)
• All magnets have a north and south pole
• Ferromagnetic materials have smaller magnetic units called domains
Not a magnet /
Non-magnetized
Magnet / Magnetized

116. Induced magnetism
• By placing a magnet near a piece of iron, the iron will become magnetized
• This is because the magnet will cause the iron domains to align themselves
 Iron loses magnetism very quickly therefore it is a temporary magnet
 Steel retains some of its magnetism so becomes a permanent magnet (until demagnetized)

117. Magnetic field lines

118. Electricity background – current
• Whilst electricity is the flow of electrons (from –ve to +ve)
• Current is the flow of positive charge (from +ve to –ve)

119. Magnetic field in a wire
• Current flowing through a straight wire will also produce a magnetic field
• A magnetic field around a coil of wire will produce a magnetic field that is
identical to a bar magnet
S
N
Right hand grip rule

120. Magnetization
1.Stroking
2. Placing solenoid inside coil of wire with direct current

121. Methods of Demagnetization
1. Heating
2. Hammering
3. Using alternating current instead of direct current

122. Permanent vs electromagnets
 Permanent magnets are designed with hard magnetic material and used for
purposes where magnetism is needed over a long period of time i.e. fridge doors
 Electromagnets use a solenoid to create a magnetic field. It is used for when a
magnetic field needs to be turned on and off i.e. scrap metal moving.

123. Electrical quantities
CAMBRIDGE IN 5 MINUTES
ELECTRICITY & MAGNETISM

124. CONDUCTORS & INSULATORS
 A conductor is something which allows electric current to flow through it freely
whereas an insulator prevents any electric current flowing through it.
 Conductors have free flowing electrons which allow the passage of electric current
through the structure i.e. metals
Insulators have tightly bound electrons that are not free to move in the structure i.e.
rubber

125. ELECTRIC CHARGE
 Electric charge is the physical property of matter that causes it to experience a force
when placed in an electromagnetic field. The unit for charge is coulombs
 There are positive charges and negative charges. Opposite charges attract and like
charges repel.

126. ELECTRIC FIELD
 A region around an electric charge where another charge experiences a force is
called an electric field.
The field lines show the direction a positive charge would move if placed in the field.
POINT CHARGE PARALLEL PLATE

127. CHARGING A BODY
 Charging a body involves the addition or removal of electrons.
 There are three main ways that we can charge a body: Friction, conduction,
induction

128. CHARGING BY FRICTION
 Different materials have different electron affinities
(i.e. love for electrons)
 When an object is rubbed over another object, the
electrons get transferred from one object to another
due to friction.
 The electrons will move from the material of lower
electron affinity to the material with higher electron
affinity
 The object that loses electrons becomes positively
charged and the object that accepts electrons become
negative charged.
 This only works for insulators because the transferred
electrons cannot be redistributed
 In metals, the gained/lost electrons are immediately
redistributed to discharge the material

129. CHARGING BY INDUCTION
 The process of charging the uncharged object by bringing another charged object
near to it, but not touching it, is called charging by induction.
A ground is simply a large object that serves as an almost infinite source of electrons or sink
for electrons. A ground contains such vast space that it is the ideal object to either receive
electrons or supply electrons to whatever object needs to get rid of them or receive them.

130. CURRENT
• Current is the rate of flow of charge
• In metals, current is due to the flow of electrons.
• The direction of conventional current is opposite to the direction of electron flow.
Electrons flow from the negative to positive terminal.
Conventional current flows from the positive to negative
terminal.
Charge (C)
Time (s)
Current (A)

131. ELECTROMOTIVE FORCE
• An electrical supply (a power pack, cell or battery) provides electrical energy which
drives charge around a complete circuit
• The electromotive force (e.m.f) of a supply is the energy provided per coulomb of
charge and is measured in volts (V).
Battery converts chemical energy into
electrical energy which is supplied to the
charge
9V battery supplies 9J of energy per
coulomb of charge
• V = EMF
• W = Work (energy)
• Q = charge in coulombs, C

132. POTENTIAL DIFFERENCE
• The potential difference or voltage across a component in a circuit is the energy required per coulomb
of charge to drive the current through that component (i.e lamp).
• Or simply, it is the amount of electrical energy converted into other forms (i.e. light) per coulomb of
charge
• It is also measured in volts (V).
• V = Potential difference
• W = Work (energy)
• Q = charge in coulombs, C
Bulb converts electrical energy into light
energy
A 1V lamp converts 1J of electrical energy into light energy per
coulomb of charge. It also means that 1J of energy per coulomb of
charge is needed to drive current through the lamp.

133. RESISTANCE
• The electrical resistance of an object is a measure of its opposition to the flow
of electric current
• Resistance is measured in ohms (Ω)
• How to find the resistance of an unknown resistor
Unknown resistor
Voltmeter
Ammeter

134. RESISTANCE OF AN UNKNWON RESISTOR
• The method before means that we are only working with one set of readings.
• If we wanted to increase accuracy, we would want multiple measurements of voltage
& current and therefore calculate resistance several times and average the results.
Known resistance
that can be altered
• By changing the resistance of the variable resistor, the current and potential
difference across the unknown resistor will change too
• As you change the resistance of the variable resistor, calculate the resistance
of the unknown resistor at each step using R = V/I
• You should end up with multiple (similar) values for the resistance of the
unknown resistor
• Average the results

135. RESISTANCE OF A WIRE
•The resistance of a wire can depend on two main things:
1. Length (of wire)
2. Area (of wire)
When the length of the wire is increased, the current must
travel further in the wire and thus resistance increases
When the cross-sectional area of the wire is increased
(i.e. larger wire diameter) the current has a greater area to
travel through so the resistance decreases.

136. ELECTRICAL WORKING
• Electrical energy is transferred from the battery or power supply in a circuit to the
components in the circuit via the electrons.
•The components will covert the electrical energy into other forms (i.e. a lamp will
convert electrical energy into light energy).
• The rate at which the energy is transformed is the power. Power can be calculated
from the formula below.

137. Electrical circuits
CAMBRIDGE IN 5 MINUTES
ELECTRICITY & MAGNETISM

138. CIRCUIT DIAGRAMS

139. SERIES VS PARALLEL CIRCUITS
Series circuit forms a single path. Parallel circuits have multiple
branching pathways for electrical
current

140. SERIES VS PARALLEL
Series Parallel

141. CIRCUIT COMPONENTS
1. Transistor
2. Potentiometer
3. Relays
4. Diode
5. Input transducers
1. Thermistor
2. Light dependent resistor

142. TRANSISTOR
• A transistor is an electrically operated switch
• It has three terminals: the base, collector, and
emitter.
• When a small current enters the base, a larger
current can flow between the collector and emitter.
• The transistor therefore amplifies the current.

143. VOLTAGE DIVIDER
A voltage divider is a simple circuit which turns a large
voltage into a smaller one. Using just two series resistors
and an input voltage, we can create an output voltage that
is a fraction of the input.

144. POTENTIOMETER
• A potentiometer can give the circuit a certain level of control i.e. volume
control
• Fundamentally, a potentiometer can made from a variable resistor.
• A variable resistor works by adjusting the path that current has to flow.
• Take a look at the diagram on the right
- Resistor length X+Y
- Wire can move up or down the resistor
- Vout is the voltage across length Y of resistor
- Changing length of X and Y by sliding the wire will change the resistance
of segment Y and therefore change Vout (i.e. V = I R)
• If this set up is connected to another component, for example an audio
unit, then the variation of output voltage can determine the volume of
the unit i.e. larger the output volume the larger the volume and vise
versa.
• Sliding wire up will INCREASE the resistance by
INCREASING length Y which INCREASES the
output voltage.
• Sliding wire down will DECREASE the resistance
by DECREASING length Y which DECREASES the
output voltage

145. RELAYS
• A relay is an electrically operated switch.
• As electricity flows through the coil, it can
“energize” the relay and it turns the coil into
an electromagnet.
• The magnetic effect of this electromagnet
“attracts” the open switch on the right and closes it
to connect the circuit.
• A small current through the left circuit can be used
to trigger the connection of the second circuit on
the right which has a much higher current flowing
through it.

146. DIODE
• A diode only allows one way flow of current through it (denoted by the arrow or
direction of the triangle in the circuit diagram).
• This property of the diode is used in the conversion of a.c. current to d.c. current
(rectification)
a.c. current – continuous change in
direction of current
d.c. current – single direction of current

147. THERMISTORS
• A thermistor’s resistance decreases as the temperature increases.
• It can therefore be used as a temperature sensor.
• The diagram below demonstrates a temperature sensitive circuit:
• When the temperature rises, the resistance of the thermistor decreases.
• This means that it takes a smaller share of the potential difference from the
power supply whilst R1 takes a larger share.
• The PD across the base (of transistor) is now large enough to switch on the
collector-emitter current.
• When a large current flows from the collector to the emitter, the bulb begins
to light.
This circuit can be used to turn on a temperature warning light for electric
devices such as cookers, hair straighteners etc.
Vout

148. LIGHT DEPENDENT RESISTORS
• The light dependent resistor (LDR) has a resistance that decreases as light intensity
increases (similar to a thermistor). This means that it can be used as a light sensor.
• The diagram below demonstrates a light sensitive circuit:
• When the light intensity decreases, the resistance increases
allowing the LDR (B) to take a larger share of the PD form
the power supply.
• This also means that the resistor (A) takes a smaller share
of the PD.
• The PD across the base is now large enough for the base
current to switch on the collector-emitter current.
• When a large current flows from the collector to the emitter,
the bulb lights.

149. Logic gates & dangers of
electricity
CAMBRIDGE IN 5 MINUTES
ELECTRICITY & MAGNETISM

150. Digital electronics
A digital system includes an input sensor and a
processor circuit, which controls the voltage to an
output device.
The processor circuit consists of a series of logic gates.
Logic gates respond to small voltages which are either
on or off. They do not respond to analogue signals.
An analogue signal varies continuously in amplitude
A digital signal has only two states: High or low (or
on and off, or 1 and 0)

151. Logic gates
Logic gates transform a digital input voltage into an
output, which depends on the type of logic gate.
The input voltages are given as 1 or 0 (on or off) and the
input/output of these logic gates can be represented on a
truth table.
A NOT gate gives an output that is opposite of the
input
An AND gate only gives an output if the input A and B
are both 1
An OR gate gives an output if input A or input B is 1
NAND gives the exact opposite output as the AND gate
NOR gate gives the exact opposite output as the OR
gate

152. Electrical hazards
Damaged insulation
Electrocution can result in death
All electrical wires are therefore insulated
A damaged insulation can therefore be hazardous as it may result in an
electricity leak.
Overheating cables
Overheating cables can result in the melting of the wire insulation and a
consequent fire.
Damp conditions
The electrical resistance of the human body drastically decreases in damp/wet
conditions.
Wet conditions coupled with unsafe handling of electrical appliances may lead
to extremely large currents passing through the body

153. Safety circuit components
Fuse
A fuse is a thin piece of wire designed to carry a set
maximum electrical current
Current that is higher than the maximum will melt from
the heat
When it melts, it breaks the circuit and thus stops the
current flowing.
Circuit breakers
Prevents excessive current passing through the circuit
It is an automated switch which interrupts current flow
when abnormally high current is detected.
A current in the coil will magnetize the iron core which
attracts the iron rocker.
The larger the current the stronger the magnetic pull
When the current becomes too high, the iron rocker will
separate from the contacts therefore breaking the circuit.

154. Earthing metal cases
An electric shock can occur if a live wire inside an electrical appliance came loose and touched the metal casing
(which is of course a conductor).
To prevent this from happening, the earth terminal can be connected to the metal casing so that the electricity can
pass through the earth instead of the human body, and therefore avoiding electrocution.
Safety circuit components

155. Electromagnetic
effects
CAMBRIDGE IN 5 MINUTES
ELECTRICITY & MAGNETISM

156. Electromagnetic induction
A conductor (such as a wire) moving across a magnetic field or a changing
magnetic field linking with a conductor can induce an e.m.f in the
conductor.
When a bar magnet is moved towards and away from a coil, it induces emf
within the coil.
Magnetic field lines of the magnet get ‘cut’ from the coil.

157. Bar magnet moving towards the coil
When the north pole of the bar magnetic is moved towards the coil
needle on the voltmeter briefly flick to the right, before returning to the
centre.
Coil cuts the magnetic field lines of the bar magnet.
This induces an emf across the coil which is measured by the voltmeter.
 The emf across the coil causes a current to flow
 The current causes the coil to act like a bar magnet.
 The direction of emf induced (and therefore the north/south pole of the coil) will
always oppose the movement of the bar magnet
 If the north pole of the bar magnet moves towards one end of the coil, a north
pole will be induced at that end

158. Bar magnet moving away from the coil
When the north pole of the bar magnetic is moved away from the coil
needle on the voltmeter briefly flick to the left, before returning to the centre.
Coil cuts the magnetic field lines in the opposite direction
The induced emf will also be in the opposite direction
 The direction of emf induced (and therefore the north/south pole of the
coil) will always oppose the movement of the bar magnet
 If the north pole of the bar magnet away from one end of the coil, a south
pole will be induced at that end to oppose movement

159. Magnitude of induced EMF
The magnitude of e.m.f induced in the coil can be increased by:
Moving the magnet faster
Putting more turns in the coil
Using a stronger magnet

160. A.C. generator
The two types of current
A.C is alternating current, where the direction of current changes periodically
D.C. is direct current, which is unidirectional
The AC generator makes a.c. current using the fundamentals of electromagnetic
induction

161. A.C GENERATOR
Pay attention to
The coil with corners
A,B,C,D
Two slip rings which
are connected to an
external circuit
AB connected to slip
ring 2, DC connected
to slip ring 1
Rotating coil
1
2

162. A.C GENERATOR
•Magnetic field lines go from north pole
to south pole
•As the coil rotates, it cuts the magnetic
field lines and induces emf and current
•In diagram, side AB will cut the
magnetic field upwards and side CD cuts
the magnetic field downwards
•As the coil rotates, eventually AB will
cut the field downwards and CD will cut it
upwards
•Since the sides have now reversed, the
direction of induced current will also
become reversed when this happens

163. FLEMINGS RIGHT HAND RULE
F
M C
C
M
F
C  D  A  B

164. DIRECTION OF INDUCED CURRENT
D
C
A
B
1
2
B  A  D  C
C  D  A  B

165. AC VOLTAGE AGAINST TIME
HORIZONTAL
VERTICAL
HORIZONTAL
VERTICAL
VERTICAL
(coil moving)
(coil moving)

166. TRANSFORMERS
A transformer increases or decreases the voltage of an alternating current.
•A step-down transformer produces an output voltage that is less
than the input voltage
• Secondary coil has less turns than the primary coil
•A step-up transformer produces an output voltage that is greater
than the input voltage
• Secondary coil has more turns than the primary coil
•A step-up transformer is use to step up voltage coming from
power stations onto powerlines that transmit electricity
• Power from power station is constant i.e. P = VI
• Higher the voltage (V) the lower the current (I)
• Lower current is good because less energy is lost as heat

167. TRANSOFMERS

168. FORCE ON A CURRENT CARRYING
CONDUCTOR

169. DC MOTOR
The poles of the magnet are curved to provide a circular magnetic field.
This helps to keep the coil in a constant magnetic field.
Each side of the coil experiences a force due to the fact that it is carrying
current within a magnetic field.
This force causes the coil to rotation (clockwise in this case).
The split-ring communicator turns with the coil and is always in contact
with the brushes (which are fixed in place) to ensure that current
continues to flow to the coil.
Each time the coil reaches a vertical position, the two sides of the
communicator swap brushes.
This reverses the flow of current to ensure that the force on each side also
become reversed. This allows the coil to continue spinning.
REMEMBER:
Conventional current direction is OPPOSITE to electron
direction

170. DC MOTOR

171. The nuclear atom
CAMBRIDGE IN 5 MINUTES
ATOMIC PHYSICS

172. The structure of an atom
- Elements are substances that are made of a single type of atom
- Every atom has a central nucleus containing smaller sub-atomic
particles called protons and neutrons
- Protons and neutrons make up most of the weight of the entire
atom
Protons have a positive charge
Neutrons have no charge
- Electrons are much smaller (virtually weightless) particles that orbit
the nucleus
Electrons have a negative charge
- A neutral atom means that it has no net charge meaning the
number of protons (+) = number of electrons (-)
- By losing or gaining electrons, atoms can become charged –
charged atoms are called ions
- Proton number = number of protons
- Nucleon (mass) number = sum of protons + neutrons

173. What makes an atom unique?
- There are currently 109 different atoms we know of
Carbon, oxygen, hydrogen etc. are all examples of atoms
- A substance made entirely of just one type of atom is called
an element
- Every atom has a different number of protons in the nucleus
- This also means that each atom has a different number of
electrons (since neutron atoms have equal
protons/electrons)
- Different atoms behave differently because of the
difference in proton/electron numbers

174. Isotopes
- Isotopes are variants of the same atom
- Isotopes have the same proton/electron number, but they have a different neutron number
- Isotopes therefore have the same proton number but different mass number
Mass numbers

175. Nuclear fission and fusion
- Two nuclei can interact by either fusing or breaking apart into smaller pieces
- Nuclear fusion is the process by which two light nuclei combine together and realse
vast amount of energy
- Nuclear fission is when an unstable heavy nucleus splits into two smaller nuclei

176. Nuclide
- For any given atom:
- Proton number (Z) is the number of protons in the nucleus
- Nucleon number (A) is the sum of protons and neutrons
The nuclide of an atom represents these values in the form of:

177. The discovery of the nucleus
- Small positive particles (alpha particles) were fired at a thin gold foil
- Pathway of particles after colliding with foil was observed and interpreted

178. Radioactivity
CAMBRIDGE IN 5 MINUTES
ATOMIC PHYSICS

179. Radioactive decay
- Radioactivity decay is a spontaneous transformation of an unstable atomic nucleus which releases radiation in the form of alpha
particles, beta particles, or gamma rays
- In alpha decay, alpha particles are emitted from the original nucleus
Each alpha particle is equal to a helium nucleus: 2 protons & 2 neutrons i.e. Z = 2 & A = 4
- In beta decay, a neutron is converted into a proton and an electron
- The electron is fired out of the nucleus whilst the proton remains
Neutron number therefore decreases by 1 & proton number increases by 1
- In gamma decay, the number of protons and neutrons are unchanged
- The gamma ray takes away some of the excess energy after the nucleus has emitted an alpha or beta particle

180. Characteristics of radioactive particles
- As mentioned above radioactive decay results in
the emission of three types of radiation alpha (α),
beta(β) , and gamma (γ)
- These are ionizing radiations meaning it has the
ability to remove electrons from atoms that they
collide with (this is called ionizing effect)
- Once an atom loses an electron, there is a charge
imbalance i.e. more protons than electrons, causing
the atom to become an positively charged ion

181. Effect of electric fields

182. Effect of magnetic fields

183. Half life
- A sample of a radioactive material decays and the activity
decreases with time
- The activity is the number of radioactive particles
emitted per second
- As number of unstable nuclei decreases, the number of
emitted particles become reduced too
- It is different to assess when a sample of radioactive
material completely stops because the activity never really
falls to zero
- But we can measure the half life instead
- The half life of a radioactive isotope is the time taken for
half of the nuclei in the sample to dacay (or the time taken
for the activity of a sample to fall to half of the original
value)

184. Safety precautions
- Ionizing radiation can kill or damage human cells
- This can cause DNA mutation that can eventually lead to cancer
- It is therefore important for people that are working with this sort of radiation to
keep safe from it
- Radiation workers wear film badges, which monitors the dose of radiation exposed
- This allows them to ensure that they are not exposed to levels that are unsafe

185. Detection of radioactivity
- G-M tube
GM tube detects ions produced when alpha, beta or gamma radiation
enters the tube
- It is attached to a counter that registers a count each time a
radioactive particle is detected
- Photographic film
- Photographic film is blackened by the presence of ionizing radiation
- The higher the number of radioactive particles, the blacker it
becomes