Energy

1
Energy

• GCSE Physics

2
Forms of energy

• 3.5.1 describe energy transfers involving the
  following forms of energy chemical, heat,
  electrical, sound, light, magnetic, nuclear,
  kinetic and potential (gravitational and strain).

3
Reference

• Physics CCEA pg 1 and 2

4
33 Longer
5
(No Transcript)
6
Some Energy Facts

• The U.S. has five percent of the world's
  population and uses 23 percent of the world's
  energy.
• In one hour, your heart works hard enough to
  produce the equivalent energy to raise almost 1
  ton of weight 1 yard off the ground.
• A decrease of only 1 in industrial energy use
  would save the equivalent of about 55 million
  barrels of oil per year, worth about 1 billion

7
Basically Energy

• In order to do work we must have a source of
  energy.
• When you eat a healthy nutri-grain bar you store
  up energy which can then be used by your muscles
  to physically do things. For a car to move it
  requires a force which is provided by mechanical
  work.
• Whenever work is done energy is needed.

8
Top Ten Types of Energy

• Kinetic energy an object has because it is
  moving.
• Light rays given off when an object glows.
• Sound vibrations caused when an object moves.
• Electrical produced when a current flows.
• Nuclear energy released when an atom splits.
• Heat moving molecules given out by fast
  vibrations.
• Chemical stored by food and fuels.
• Elastic potential energy stored in a stretched
  or squashed object.
• Gravitational potential energy an object has
  because of its position above the ground.
• Magnetic- energy which exists between magnetic
  materials.

9
Energy Transfer

• Energy tends to change form- take for example the
  food we eat. The chemical energy is then changed
  into kinetic energy (as well as other types of
  energy) for our bodies to do useful work!

10
Energy Transfer
The Dynamo
Output (wasted) energy- heat/sound
Output (useful) energy- electrical/light
Input energy Kinetic
11
The Unit of Energy

• Energy is measured using the Joule or the
  kiloJoule (1000 Joules)
• Check out what energy values can do what work

12
(No Transcript)
13
Conservation of Energy

• 3.1.11 understand that energy is conserved and
  describe energy changes in terms of the principle
  of conservation of energy.

14
Conservation of Energy

• Reference- Page 2
• Write out the law of conservation of energy
• Another way of stating this law is that every
  time energy is transferred the input energy will
  be equal to the total output energy (sum of the
  useful energy and wasted energy)

15
Example

• Every second a car transfers 200 kJ energy in the
  petrol to 80 kJ of moving energy. Represent this
  transfer in a diagram.

Output (useful) energy- Kinetic 80 kJ
Input energy Chemical 200 kJ
Output (wasted) energy- heat/sound 120 kJ
Input Energy Output Energy 200kJ 80kJ 120kJ
16
Try this question-

• A power station uses 1,000,000 kJ of chemical
  energy every second, but it only gives out
  400,000 kJ of electrical energy each second. What
  has happened to the input energy?
• Draw an energy transfer diagram to represent the
  transfer (include quantities and units).

17
Output (useful) energy- Electrical 400 000 kJ
Input energy Chemical 1 000 000 kJ
Transforms to Kinetic
Output (wasted) energy- Heat/Sound 600 000 kJ
The input energy has changed form to kinetic and
then to both useful electrical energy and wasted
energy. The input energy and output energy totals
are equal as energy is conserved.
18
Energy Resources

• 3.1.3 explain how energy resources such as wind
  and fossil fuels are ultimately dependent on the
  Suns energy.

19
Tracing Back the source of all energy

• Listening to a song, electrical energy sent to
  your brain

Loud Speaker Sound Energy
Nerve Cell Electrical Energy
Plug and wires Electrical Energy
Power Station Kinetic Energy
Fuel Chemical Energy
Plants Chemical Energy
20
the Primary Source
The Sun Nuclear Energy
21
Energy Resources

• 3.1.2 recall that there is a variety of energy
  resources, to include, oil, gas, coal, nuclear,
  biomass, wind, wave, solar, geothermal, tidal and
  hydroelectric and distinguish between renewable
  and non-renewable.

22
Types of Energy Resources

• http//www.educapoles.org/loader.swf?pathdocs/pro
  jects/flash_animations/energy_7_different_kinds_of
  _energy_061205.swflgen

23
Energy Resources

• 3.1.4 describe the environmental implications of
  the use of energy resources, limited to
  generation of electricity by fossil fuels,
  nuclear fuels, hydroelectric power, wind farms,
  waves and tides. Appreciate the effect on the
  environment of the use of these energy resources,
  limited to the contribution of burning fossil
  fuels to greenhouse effect (brief outline only),
  land/sea use and nuclear waste.
• 3.1.5 evaluate the advantages and disadvantages
  of using various energy resources to generate
  electricity. This should take into consideration
  reliability, how quickly the different types of
  power station can respond to changes in demand,
  the costs of building, operating and
  de-commissioning power stations and any
  additional information, including quantitative
  information, with which they are provided.

24
How is electricity generated?

• An electromagnet generator (a complex version of
  a dynamo)
• A turbine

25
Energy transfer in a Power Station

• http//www.eon-uk.com/EnergyExperience/497.htm

26
Energy Resource Questions

• In class
• Complete questions 5, 6, 8, 9, 14 and 15 on page
  7 and 8
• For Homework
• Complete questions 1- 3 on page 29

27
Geothermal Energy
The rocks not too far below the surface are quite
hot, 500C about 1 km down.
28
Geothermal

• In some areas there are 'hotspots' where the
  temperature below the surface is very high. This
  is usually near where the earth's tectonic plates
  meet.

29
Geothermal Energy

• Water can be heated by these hot rocks which lie
  beneath the Earths surface.
• The steam from the hot water can be used to turn
  a turbine and generate electricity!

30
Geothermal Energy
Advantages Disadvantages
- Renewable energy resource - Huge quantities of energy available - Deep drilling is very difficult - Drilling can also be expensive
31
Biomass
harvesting switchgrass
32
Biomass

• Biomass is a renewable energy source from wood,
  manure, garbage and agricultural waste.
• When biomass is burned, energy is released as
  heat that can be transformed into electricity or
  fuel.
• Manure can also be turned into electricity using
  the methane gas the solid manure gives off when
  put into a digester.

http//www.energyquest.ca.gov/story/chapter10_flas
h/index.html
33
Biomass
Advantages Disadvantages
It makes sense to use waste materials where we can. The fuel tends to be cheap. Less demand on the Earth's resources. Collecting the waste in sufficient quantities can be difficult. We burn the fuel, so it makes greenhouse gases. Some waste materials are not available all year round.
34
Crossword Puzzle

• http//www.energyquest.ca.gov/games/crossword_puzz
  les/renewable_energy.html

35
Efficiency

• 3.1.14 recall that efficiency is a measure of how
  much energy is transferred in an intended way and
  recall and use the relationships between
  efficiency, input energy and output energy.

36
Efficiency

• Reference Page 12
• - Read page 12 for extra notes on Efficiency

37
Efficiency is a measure of how good a device is
at changing energy from one form to another.
All devices waste energy, so the efficiency of a
device is never 100.
Energy efficient light bulbs are more efficient
than normal light bulbs because they w____ less
energy, and more of the e______ energy that they
are supplied with is converted into l___ energy
and not h___.
aste
lectrical
ight
eat
There is a formula that allows you to calculate
the efficiency of a device or of a process.
38
The efficiency formula
We can express efficiency mathematically using
the equation
Efficiency Useful energy out Total energy in
The efficiency formula is unusual because it has
no units. It is a number between 0 and 1 or a
percentage .
Useful energy measured in Joules (J)
Total energy measured in Joules (J)
39
Efficiency for a bulb

• If you have a filament bulb and it is
  supplied with 100J of electrical energy which it
  converts to 45J of light energy.
• How much energy is wasted?
• In what form is the energy wasted?
• What is the efficiency of the bulb?

55J
Efficiency Useful Total
45J/100J 0.45 or 45
heat