1. Magnetism

2. Magnetism Magnetism – Forces exerted by magnets
Lodestones – rocks that are naturally magnetic
Found in Magnesia in Greece
Used by Chinese to navigate ships

3. Magnetic Poles
Magnetic poles – one of the regions on a magnet that produces magnetic forces
Like poles repel
Opposite poles attract
Compass: end that points northward is the north seeking pole, end that points southward is the south seeking pole

4. Magnetic Field
Magnetic field – the space around a magnet, in which a magnetic force is exerted
Shape of the field is revealed by magnetic field lines
Every spinning electron is a magnet, most atoms’ electrons spin in different directions cancelling their magnetic force
Opposite poles
Similar poles
Magnetic Field

5. Choose words to fill in the blanks:
Magnetism is a force exerted by _______. Magnets are objects surrounded by a magnetic field. A magnetic ____ is the space around a magnet, in which a magnetic ____ is exerted. Every spinning ______is a magnet, most atoms’ electrons spin in different directions cancelling their magnetic force.
Electron
force
Field
Magnets

6. Choose words to fill in the blanks:
Each magnet has two ____, a north and a south pole. The magnetic poles are one of the ______ on a magnet that produces magnetic forces. Like poles will ______ each other while opposite poles will ______ each other.
attract
regions
poles
repel

7. Electromagnetic Induction
Magnets moved near—or even inside coils of wire induce (cause) a current in the coil. The more coils there are, the more current there is.

8. Electromagnetic Induction
Moving wire and keeping the magnet stationary is the same as moving the magnet and keeping the wire stationary.

9. Faraday’s Law
The induced voltage in a coil is proportional to the product of the number of loops and the rate at which the magnetic field changes within those loops

10. Electromagnet A moving charge produces a magnetic field.
An electric current produces a magnetic field
Magnetic field around a wire forms concentric circles

11. Electromagnets
A current-carrying coil of wire with many loops is an electromagnet

12. Steam powered generator
Generators
Hand powered generator
Device that rotates a coil of wire in a stationary magnetic field inducing a voltage in the coil Converts mechanical energy into electrical energy
Steam powered generator

13. Electric Motors
A permanent magnet is used to produce a magnetic field in a region where a loop of wire is mounted so that it can turn about an axis.
Brushes – Parts of the wire that brush against contacts in a motor
Armature – in larger motors, many coils of wire are wound about an iron cylinder

14. Steam powered generator
Turbine
Generator, where the armature is connected externally to a wheel The wheel may be powered by wind, falling water or steam
Steam powered generator

15. Motor Effect vs Generator Effect
Motor effect – when a current in a wire moves perpendicular to a magnetic field, there is an upward force on the electrons that move the wire
Generator effect – When a wire with no initial current is moved in a magnetic field, the electrons in the wire experience a deflecting force perpendicular to their motion

16. Transformers
Alternating current in the primary coil causes the north-south polarity of the electromagnet to change. Increasing or decreasing voltage through electromagnetic induction

17. Transformers

18. current electromagnet motor electric generator wire
Choose words to fill in the blanks:
As an ______ current or moving charge passes through a wire it produces a magnetic field. This magnetic field around a ____ forms concentric circles. A current-carrying coil of wire with many loops forms an ____________ . Magnets moved near—or even inside coils of wire induce (cause) a ______ in the coil. Electromagnets can be used as a ______ or _________ or simply as a magnet that can be turned on and off.
current
electromagnet
motor
electric
generator
wire

19. mechanical turn motor wire
Choose words to fill in the blanks:
An electric ______ is made when a permanent magnet is used to produce a magnetic field in a region where a loop of wire is mounted so that it can ____ about an axis. As current passes through the ____ , the wire spins as it is repelled and attracted to the magnet. The motor converts electrical energy into ___________ energy.
mechanical
turn
motor
wire

20. Choose words to fill in the blanks:
An electric _________ is a device that rotates a coil of wire in a stationary magnetic field inducing a _______ in the coil. The generator ________ mechanical energy into _________ energy.
converts
generator
electrical
voltage

21. Energy Transformations
Energy Changes!!!!!!!

22. Energy Energy is required to do work.
Fuels are burnt to release energy
The Sun is the ultimate source of most of our energy on Earth. 22

23. The Law of Conservation of Energy
The total amount of energy on earth stays the same; it can be neither created nor destroyed.
It can only be converted from one form to another.
If energy seems to disappear, then scientists look for it – leading to many important discoveries.

24. Law of Conservation of Energy
In 1905, Albert Einstein said that mass and energy can be converted into each other.
He showed that if matter is destroyed, energy is created, and if energy is destroyed mass is created. E = mc2

25. Conservation of energy
Energy cannot be created or destroyed. It can only be transformed from one form to another form.
Conservation of energy also means that the total energy in the universe stays constant. 25

26. “Law of Conservation of Energy” Energy can not be created or destroyed, it can only change its form.
To Conserve means:
1. to keep
2. to preserve
3. to maintain
If energy seems to get lost during a process, then we should look for it !!

27. Pendulum oscillation
GRAVITATIOINAL POTENTIAL ENERGY
MAXIMUM
ZERO
MAXIMUM
MINIMUM
KINETIC ENERGY
The total energy, gravitational potential plus kinetic, remains the same if there are no significant resistive forces 27

28. Choose words to fill in the blanks:
According to the law of conservation of energy, during transformations the _______ amount of __________ stays the same. Energy can be not be ___________ or ____________ ; it can only change its form.
created
destroyed
energy
total

29. Energy Conversion
Energy can be changed from one form to another. Changes in the form of energy are called energy conversions.
Whenever energy is converted, some heat will be released or lost in the process

30. Energy conversions
All forms of energy can be converted into other forms.
The sun’s energy through solar cells can be converted directly into electricity.
Green plants convert the sun’s energy (electromagnetic) into starches and sugars (chemical energy).

31. Other energy conversions
In an electric motor, electrical energy is converted to mechanical energy.
In a battery, chemical energy is converted into electrical energy.
The mechanical energy of a waterfall is converted to electrical energy in a generator.

32. Energy Conversions
In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy.

33. Choose words to fill in the blanks:
Energy can be changed from one _______to another. Changes in the form of _______ are called energy __________________ . Whenever energy is converted, some _____ will be released or lost in the process.
conversions
form
energy
heat

34. Forms of energy Energy can exist in many forms. 1. THERMAL
or HEAT ENERGY
This is the energy of an object due to its temperature.
2. LIGHT ENERGY
This is energy in the form of visible electromagnetic radiation. 34

35. This is the energy transferred by an electric current.
3. ELECTRICAL ENERGY
This is the energy transferred by an electric current.
4. SOUND ENERGY
This is energy in the form of a sound wave. 35

36. 5. KINETIC/MECHANICAL ENERGY
This is the energy possessed by a moving object.
Kinetic energy increases as the object’s speed is increased.
Also often called ‘Movement energy’ 36

37. This is energy that is released when chemical reactions take place.
6. CHEMICAL ENERGY
This is energy that is released when chemical reactions take place.
Sources of chemical energy include:
fuel, food and batteries.
7. NUCLEAR ENERGY
This is energy that is released when nuclear reactions take place.
This is the source of the Sun’s energy. 37

38. This is the energy possessed by an object due to its position.
Gravitational potential energy being converted into kinetic energy.
8. POTENTIAL ENERGY
This is the energy possessed by an object due to its position.
Gravitational Potential Energy
The gravitational potential energy of an object increases if it is raised upwards.
Elastic Potential Energy
This is the energy stored in a stretched or squashed object
- also known as strain energy 38

39. Chemical  Heat Mechanical

40. Light
Chemical
Electrical

41. Light
Thermal
Electrical

42. Light
Chemical

43. Electrical
Mechanical

44. Thermal
Electrical
Mechanical

45. Electrical
Sound
Chemical
Mechanical
Light
Thermal

46. Sound
Electrical

47. Chemical
Thermal

48. chemical mechanical electricity Solar
Choose words to fill in the blanks:
All forms of energy can be converted into other forms, examples include:
The sun’s energy through _______ cells can be converted directly into ______________ .
Green plants convert the sun’s energy (electromagnetic) into starches and sugars (_________________ energy).
In an electric motor, electrical energy is converted to ___________________ energy.
chemical
mechanical
electricity
Solar

49. chemical mechanical fuel waterfall
Choose words to fill in the blanks:
All forms of energy can be converted into other forms, examples include:
In a battery, __________ energy is converted into electrical energy.
The mechanical energy of a ___________ is converted to electrical energy in a generator.
In an automobile engine, _____ is burned to convert chemical energy into heat energy. The heat energy is then changed into _________________ energy.
chemical
mechanical
fuel
waterfall

50. Sankey Diagrams
These are energy flow diagrams that show how well a device uses energy.
The width of the flow arrows is proportional to the amount of energy
Wasted energy is shown flowing downwards.
INPUT
Device
USEFUL OUTPUT
WASTED OUTPUT 50

51. Energy flow diagrams GENERAL DIAGRAM DEVICE CAUSING ENERGY CHANGE
INPUT ENERGY
WASTED ENERGY
USEFUL OUTPUT ENERGY 51

52. Choose words to fill in the blanks:
Energy flow ____________ show how _________ is transformed as it moves through a _____________ . Accounts for the thermal energy (_______ ) given off during that transformation.
diagrams
heat
energy
system

53. An electric light bulb lightbulb electrical energy light energy
heat energy 53

54. Microphone
sound energy
electrical energy
microphone
heat energy 54

55. Car engine car engine chemical energy kinetic energy
heat & sound energy 55

56. Photosynthesis
light energy
chemical energy
plants
heat energy 56

57. Deep thoughts
Which of the forms of energy are most important to us in our daily lives?
Electricity itself moves, but how does it cause other things to suddenly move?
Name a few devices in which electricity causes something to move in a circle.

59. Energy Conversions Fuel (chemical to thermal)
Water (thermal to mechanical)
Steam turbine (mechanical to mechanical)
Generator (mechanical to electrical)
Toaster (electrical to thermal)
Toast (thermal to chemical)
Condenser (thermal to chemical)
Emission control (chemical to thermal)

60. Complete the table below:
Device
Input energy
Main output energy
Electric motor
electrical
Car brakes
heat
gravitational potential
Kinetic/mechanical
Candle
light
Generator
Kinetic/mechanical
kinetic
Falling object
chemical
kinetic 60

61. Useful and wasted energy
Useful energy is energy transferred to where it is required in the form that it is wanted.
Other forms of energy are referred to as ‘wasted’.
Wasted energy spreads out into the surroundings.
This is usually in the form of heat energy causing the energy changing device and its surroundings to become warmer. It is very difficult to ‘concentrate’ this energy again to make use of it. 61

62. Energy efficiency
Energy efficiency is a measure of how usefully energy is converted by a device.
efficiency =
useful energy output
total energy input
As the useful energy output can never be greater than the energy input the efficiency can never be greater than 1.0 62

63. Energy efficient light bulbs
These produce more useful light energy for the same amount of input electrical energy.
They waste less energy to heat. 63

64. Improving efficiency Decrease loss to heat by:
Reducing friction by using a lubricant (eg oil).
Reducing electrical resistance in electrical circuits.
Reducing air resistance by using streamlined shapes.
Reduce loss to sound by tightening the loose parts of machinery. 64

65. Efficiency Measure Wasted Heat Required
Choose words to fill in the blanks:
Efficiency Measure Wasted
Heat Required
Useful energy is transferred to where it is ____ in the form that it is wanted. Other forms of energy are referred to as ‘____ ’ or given off in the form of heat. Strategies to reduce this ____ loss are intended to improve the ____ of a device. Energy efficiency is a ____ of how usefully energy is converted by a device.

66. Efficiency Measure Wasted Heat Required
Choose words to fill in the blanks:
Efficiency Measure Wasted
Heat Required
Useful energy is transferred to where it is required in the form that it is wanted. Other forms of energy are referred to as ‘wasted’ or given off in the form of heat. Strategies to reduce this heat loss are intended to improve the efficiency of a device. Energy efficiency is a measure of how usefully energy is converted by a device.

67. Conserve Reduce Light bulbs Wasting
Choose words to fill in the blanks:
Conserve Reduce
Light bulbs Wasting
Energy efficient ____ ____ are designed to produce more useful light energy for the same amount of input electrical energy by ____ less energy to heat. Use of energy efficient light bulbs is one strategy to conserve or ____ our consumption of energy. Within our homes there are many strategies we can use to ____ energy.

68. Conserve Reduce Light bulbs Wasting
Choose words to fill in the blanks:
Conserve Reduce
Light bulbs Wasting
Energy efficient light bulbs are designed to produce more useful light energy for the same amount of input electrical energy by wasting less energy to heat. Use of energy efficient light bulbs is one strategy to conserve or reduce our consumption of energy. Within our homes there are many strategies we can use to conserve energy.

69. Question 1
Calculate the efficiency of an electric motor if it produces 48J of useful kinetic energy when supplied with 80J of electrical energy.
efficiency =
useful energy output
total energy input
efficiency = 48J ÷ 80J
efficiency of the motor = 0.6 69

70. Question 2
Calculate the useful light output of a light bulb of efficiency 0.20 when it is of an electric motor if it supplied with 400J of electrical energy.
efficiency =
useful energy output
total energy input
0.20 = useful energy ÷ 400J
useful energy = 0.20 x 400J
light output = 80J 70

71. Percentage efficiency
percentage efficiency = efficiency x 100
The greater the percentage of the energy that is usefully transformed in a device, the more efficient the device is.
The maximum percentage efficiency is 100% 71

72. Question 3
Calculate the percentage efficiency of a light bulb if it produces 30J of light when supplied with 240J of electrical energy.
efficiency =
useful energy output
total energy input
efficiency = 30J ÷ 240J
= 0.125
% efficiency = efficiency x 100
Percentage efficiency of light bulb = 12.5% 72