1. Physics Unit 1 Revision
Energy

2. Energy Thursday, 08 November 2018
Energy Stores
Learning Outcomes
By the end of this lesson you will be able...
To describe how energy can be stored.
To describe how energy can be transferred.
To understand the conservation of energy.
Keywords
Conservation, wasted, useful
Starter: List all the forms of energy you know.

3. Forms of energy
Electrical energy
Heat energy
Light energy
Sound energy
Chemical energy
Kinetic energy
Gravitational potential energy
Elastic potential energy

4. ENERGY TRANSFER Law of conservation of energy
Energy can neither be created or destroyed, but it can be transferred usefully, stored or dissipated.

5. EXAMPLES OF ENERGY TRANSFER
Electrical  heat + sound + light
This means that the kettle is using electrical energy and it is transferring it into heat, sound and light.
Useful energy is heat and light
Wasted energy is sound and…

6. EXAMPLES OF ENERGY TRANSFER
Electrical  heat + sound + light
Wasted energy is energy which is dissipated so that it is stored in les useful ways.
E.g. the heat in the surroundings

7. Energy transfer Light energy Heat energy Electrical energy
Which one is the wasted energy?

8. Energy transfers in a petrol mower

9. Gravitational
potential energy
Kinetic energy

10. Potential energy P.E + K.E P.E + K.E Potential energy
just before it hits the ground
Electrical energy
from engine

11. Energy Thursday, 08 November 2018
Sankey and Efficiency
Learning Outcomes
By the end of this lesson you will be able...
To interpret Sankey diagrams
To draw Sankey diagrams
To calculate efficiency
Keywords
Useful
Starter: If something is efficient what does this mean?
Homework due _________________

12. Gravitational potential energy
Kinetic energy
Heat energy
Gravitational potential energy
Electrical energy
Chemical energy
Light energy
Watch this space!
Write down which form of energy is the useful energy . You will have 8 seconds for each slide.

13. You need to learn this equation:
Efficiency = 𝑢𝑠𝑒𝑓𝑢𝑙 𝑜𝑢𝑡𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟 𝑡𝑜𝑡𝑎𝑙 𝑖𝑛𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟 x 100
Efficiency = = 0.2 x 100 = 20%

14. Use 1 small square on a graph paper to represent 1 J of energy
7 squares = 7 joules
10 Joules electrical energy
3 squares = 3 joules
1 square is 1 joule of energy

15. Energy Thursday, 08 November 2018
Kinetic energy
Learning Outcomes
By the end of this lesson you will be able...
To define kinetic energy.
To recognise what factors affect the kinetic energy of an object.
To use the equation for calculating the kinetic energy of a moving object.
Keywords
KE, velocity
Starter: What is kinetic energy? Give some examples of objects with kinetic energy.

16. Kinetic energy = ½ x mass x velocity2
Any object that moves will have kinetic energy.
The amount of kinetic energy an object has can be found using the formula:
Kinetic energy = ½ x mass x velocity2
Joules kg m/s
KE = ½ mv2
You need to learn this equation

17. Energy Thursday, 08 November 2018
Potential energy
Learning Outcomes
By the end of this lesson you will be able...
To define gravitational and elastic potential energy.
To recognise what factors affect the potential energy of an object
To use the equation for calculating gravitational potential energy and elastic potential energy
Keywords
Elastic, gravitational
Starter: Can you recall the equation for acceleration?

18. Ep
m x g x h

19. GPE = mass x change in height x gravitational field strength
Example question: Calculate change in GPE, when a 1000kg aeroplane, takes off up to a height of 500m.
Gravitational field strength on earth= 10N/Kg
=1000kg x 500m x 10N/kg
=5,000,000J

20. Elastic potential energy
A force acting on an object may cause the shape of an object to change. Elastic objects can store elastic potential energy if they are stretched. For example, this happens when a catapult is used.

21. Changing shape
Elastic objects can also store elastic potential energy when they are squashed. For example, this happens when a squash ball is dropped onto a hard surface.
Work is done on an elastic object when its shape changes and it stores elastic potential energy. It is possible to calculate the amount of energy stored when stretching or squashing an elastic material, what do you think this might depend on?

22. Energy Thursday, 08 November 2018 Kinetic energy + Potential energy
Learning Outcomes
By the end of this lesson you will be able...
To describe that energy is conserved using GPE and KE
To calculate changes in GPE
Keywords
Conservation
Starter:
What’s your favourite rollercoaster ride? What energy changes take place on it?

23. Energy Thursday, 08 November 2018
Power
Learning Outcomes
By the end of this lesson you will be able...
To recap how to calculate work done and power.
To calculate the power of a person.
Keywords
Work done
Starter: Can you remember the units of work done?
What is the difference between mass and weight?

24. Work and energy
When a force causes a body to move through a distance, energy is transferred and work is done.
work done = energy transferred.
Both work and energy are measured in joules (J). 24

25. Work and friction
Work done against frictional forces is mainly transformed into heat.
Rubbing hands together causes them to become warm.
Brakes pads become hot if they are applied for too long. In this case some of the car’s energy may also be transferred to sound in the form of a ‘squeal’ 25

26. The work equation
work done = force applied × distance moved in the direction of the force
W = F x d
work, W is measured in joules (J)
force, F is measured in newtons (N)
distance, d is measured in metres (m) 26

27. W F d also: force = work done ÷ distance moved and:
distance = work done ÷ force W F d 27

28. Power (P)
Power is the rate at which energy is transferred of the rate of work done.
power = work done power = energy
time taken time taken
P = W P = E
t t
power, P is measured in watts (W)
work done, W energy, E is measured in joules (J)
time, t is measured in seconds (s)
One watt is the same as one joule per second. 28

29. Energy Thursday, 08 November 2018
SHC
Learning Outcomes
By the end of this lesson you will be able...
To understand the idea of specific heat capacity of a material.
To calculate SHC by investigation
Key phrase
Specific heat capacity
Starter:
Which is the fastest way to cook? Boiling or frying? Why do you think that is?

30. SHC
The specific heat capacity of a material is the amount of energy needed to raise the temperature of 1kg of the material by 1°C. It’s units are J/kg°C.

31. SHC
You do not need to learn this equation

32. SHC

33. Energy Thursday, 08 November 2018
SHC theory
Learning Outcomes
By the end of this lesson you will be able...
To understand how materials with different specific heat capacities are used.
Keywords
No new words
From last lesson… what is the equation for specific heat capacity, can we put it into a triangle?

34. E m x c x θ What does each symbol mean?
What are the units for each symbol?
You do not need to learn this equation E
m x c x θ

35. Energy Thursday, 08 November 2018 Reducing Unwanted Energy Transfers
Learning Outcomes
By the end of this lesson you will be able...
To describe how to reduce heat transfer in buildings.
To describe how to reduce friction in machines
Keywords
Insulation, lubrication, thermal conductivity
Starter: How do we insulate our houses... Make a list

36. Loft Insulation
Glass fibres in the insulation are long and thin so don’t conduct heat very well.
The material is mainly air which is a bad conductor (because the particles are a long way apart).
The glass fibres stop the air circulating so there is no heat transfer by convection through the insulating material.
NB the ceiling stops the warm air escaping from the room.

37. Cavity Wall Insulation
Two layers of masonry mean that moisture can’t soak through the wall (reducing cooling by evaporation).
The air space does not insulate well because although air is a bad conductor it can circulate and transfer heat by convection.
The air space is filled with foam, fibres or polystyrene balls so that the air cannot circulate and heat transfer by convection is reduced.
Modern cavity walls are built with solid foam panels in the cavity. These are covered in aluminium foil to reduce heat transfer by radiation.

38. Payback time
All these examples of insulation cost money to install but save money on heating bills. The time it takes to pay back the cost of the insulation because of the savings made by installing it is called the payback time.
payback time = initial cost of installing insulation (£) (years) savings per year (£/year)

39. Energy Thursday, 08 November 2018
Energy Resources
Learning Outcomes
By the end of this lesson you will be able...
To describe different energy resources including the advantages and disadvantages of each.
To determine the most suitable fuel for a particular use depending on the characteristics of the fuel.
Keywords
Renewable, reliable
Starter: Write down all the different energy resources you know.
Extra challenge: Next to each write R (renewable)
or NR (non-renewable)

40. Geothermal Energy – energy from the Earth
Deep underground, the Earth’s rocks are naturally very hot. We can turn their heat energy into electrical energy to use in our homes – we call this ‘geothermal energy’.
Cold water is pumped below the ground.
Hot rocks heat the water, turning it into steam.
The steam is used to generate electricity.
Renewable
No pollution (CO2), because nothing gets burned
Doesn’t damage the environment
Very few places in the world where you can do this
Costs a lot of money to drill deep into the ground

41. Wave Energy – energy from sea waves
The sea’s waves have kinetic energy. Using machines that bob up and down in the waves, this energy can be turned into electrical energy which we can use in our homes.
wave energy machines bobbing up and down in the waves
Need lots of machines to get a reasonable amount of energy
The machines costs a lot of money
The machines can look ugly
The machines can be damaged by storms
Renewable
No pollution (CO2), because nothing gets burned

42. Hydroelectric Energy – energy from rivers
The water flowing in a river has kinetic energy. We can turn this into electrical energy to use in our homes. We usually need to build a dam, and let the water flow through it gradually.
Renewable
No pollution (CO2), because nothing gets burned
We can store the water up high, and then whenever we need the energy we can let the water out
Costs a lot of money to build a dam
The dam can ruin the local environment, because it changes where the water naturally flows. Some animals and plants may die.

43. Tidal Energy – energy from sea tides
If you’ve ever been to the coast, you may have noticed that the sea level goes up and down, because of tides. When the tide is high, the water has lots of gravitational potential energy, which we can turn into electrical energy to use in our homes.
At high tide, we trap the water behind a dam.
At low tide, the water is released, and its energy is used to generate electricity.
Renewable
No pollution (CO2), because nothing gets burned
Reliable, because there are always two tides every day
Cheap to run, once it’s built
Costs a lot to build the dam
The dam may cause local flooding

44. Solar Energy – energy from the Sun
The Earth gets heat and light energy from the sun all the time. Can we use it – yes we can! The Sun’s energy can either be:
changed into electrical energy to use in homes, using solar cells;
or used to heat water for homes, using solar panels.
Renewable
No pollution (CO2), because nothing gets burned
Solar cells and solar panels are expensive
Only works if it’s sunny!

45. Wind Energy – energy from the wind
Using wind turbines, we can turn the kinetic energy of the wind into electrical energy which we can use in our homes. This is ‘wind energy’.
Renewable
No pollution, because nothing gets burned
Turbines are quite cheap and easy to build, so they can be used even in poor countries
Turbines can be ugly and noisy
Only works if it’s quite windy! If the wind stops, you get no energy.

46. Biofuel/biomass Energy – energy from plants
The chemical potential energy stored in things that were once alive (e.g. trees) can be turned into heat energy by burning them. (We can also turn it into electrical energy to use in our homes.)
Trees absorb the sun’s energy. The trees change this energy into chemical energy, which they store inside themselves.
When we burn wood, we turn this energy into heat, which is useful for cooking and heating.
Renewable – as long as we keep planting trees to replace the ones we cut down
Doesn’t need any special equipment, so it can be used very easily, even in poor countries
Doesn’t add to the greenhouse effect
Large areas of land are needed to grow enough trees

47. End of Physics Unit 1 Revision
Energy