Unit B – Energy Transformations

1. Unit B – Energy Transformations

2. Chapter 5 – Energy Transformations • In this chapter you will learn: • how to identify different types of energy • that some energy conversions absorb energy and some release it • how energy is converted and that energy is lost with each conversion • about the law of conservation of energy

3. 5.1 - Energy • Energy is the ability to do work • Energy causes changes in: • temperature • direction of motion • speed • shape

4. Two Types of Energy • Potential Energy is stored energy • Examples: • chemical energy stored in the food you eat • gravitational potential energy when you are at the top of a hill • Kinetic Energy is energy due to motion • Examples: • the flow of electrons (electricity) • skiing down a mountainside

5. 5.2 – Many Forms of Energy • Energy on the Earth originates as solar energy from the Sun • Energy from the Sun is converted by plants: solar  chemical  kinetic (photosynthesis) (cellular respiration)

7. Energy from the Sun is converted by wind turbines: solar  wind  electricity • Energy from the Sun is converted by solar panels: solar  electricity

8. 5.3 – Understanding Energy Conversions • Energy must get converted so that it is useful • Energy entering a system is called input energy • System that changes the system is called the converter • Energy leaving the system is called the output energy

10. When energy is converted from one form to another, thermal energy is produced • Sometimes heat energy is useful: • ie. heat released during cellular respiration heats your body • ie. chemical reaction in a “hot pack” • When the thermal energy is not useful, it is called waste energy: • ie. heat from a light bulb • ie. heat from a car engine

11. 5.4 – Conservation of Energy • Whenever energy is converted by a device, the amount of energy coming out is equal to the amount of energy coming in

12. What types of energy are produced by a blow dryer? • Thermal energy provides the heat to dry • Kinetic energy in the moving air • Some electricity is converted to sound energy • The glowing elements produce light energy • Friction produces thermal energy that is not used to dry your hair.

13. 5.5 – Energy Conversion Systems • Some output energy produced during an energy conversion is useful (useful output energy) and some output energy is not (waste output energy)

14. No energy conversion is 100% efficient • When energy is converted from one form to another, thermal waste energy will always be produced.

15. Pages 98 - 113 Chapter 6 – Electric Energy at Home

16. Chapter 6 – Electrical Energy at Home • In this chapter you will learn : • about technologies that various forms of energy into electricity • how appliances convert electricity into other forms of energy • how to calculate the efficiency of electrical devices • how to measure electricity and calculate power • why it is important to conserve energy

17. 6.1 – Generating Electrical energy • In the early 1800s, Michael Faraday discovered that moving a magnet through a coil of copper wire generated an electrical current • Faraday used these observations to make the first electric generator

18. A generator is a device that makes electricity • Most electric energy is made in a generator • A generator consists of A magnet and a coil of wire.

19. Electrical current can be increased by: • Increasing the number of coils • Using a stronger magnet • Moving the magnet/ wire faster

20. Energy conversion in a generator: • Not all of the kinetic energy is converted into electrical energy. If energy is conserved during a conversion, what happened to the rest of the kinetic energy?

21. Chapter 6.2 – Generating and Distributing Electric Energy Turbines and Generators • Generators contain one or more turbines

22. In order to make electricity, turbines need to be connected to a generator. • As the blades of the turbine turn, their kinetic energy is transformed into kinetic energy in the generator. • Kinetic energy in the generator is transformed into electrical energy kinetic  electrical

23. Power Generating Plants • Hydro-electric, thermo-electric, and thermonuclear plants all use turbines and generators to produce electricity.

24. Coal-fired Thermo-electric Generation • Coal in Alberta is cheap and plentiful • Emissions pass through a “scrubber” to remove some of the harmful chemicals from the smoke

25. How it works: • Coal is pulverized and combusted • Thermal energy from burning coal converts water to steam • High-pressure steam causes turbine blades to turn • The spinning turbine turns the generator, producing an electric current • The steam leaves the turbine and enters a cooling chamber before returning to the furnace.

27. Hydro-electric Plant • The kinetic energy of falling water is used to produce electricity

28. Hydro-electric generation • What are some possible advantages and disadvantages to using hydro-electric power?

29. Thermonuclear Power Plant • Uranium atoms are split by nuclear fission to release large amounts of thermal energy. • Thermal energy makes steam. • Steam is used to turn turbines, producing electricity.

31. What are some of the advantages and disadvantages of producing electricity with nuclear energy? Japan Nuclear Reactor Explanation

32. Distributing Power - The Power Grid • Electrical generating plants are often located far away from communities. • Electricity must be transmitted hundreds of kilometers along power lines. • About 10% of energy is wasted as thermal energy as it moves along the power lines. • Constructing power plants close to communities creates environmental concerns.

33. Quick Review!

34. 6.3 – Electrical Energy and Power • We can measure how fast energy is transferred from one object to another; how fast work is done • Power is a measure of the rate of energy transfer

35. The formula used to calculate power is: power is measured in Watts (W) energy is measured in Joules (J) time is measured in seconds (s) • A generator produces 2 J of energy every second. How many watts of power does it produce?

36. An aquarium light bulb uses 7 J of electric energy in one second. How many watts of power does it consume in 3 seconds?

37. Speakers on a computer use 40 J of electric energy. How many watts of power do the speakers consume in one minute (60 seconds)?

38. You can calculate how much electric energy is consumed by a device by re-arranging the formula: • The formula used to calculate how much energy is used is: Where energy is measured in watt hours (Wh) power is measured in watts (W) time is measured in hours (h)

39. How much electric energy does a 60 W light bulb use if it is left on for 2 hours? • How much electric energy does a 240 W fan use if it is left on for 1.5 hours?

40. 6.4 – Efficiency and Saving Energy • Some devices are better than others at converting electrical energy into useful output energy • Which of these devices is more efficient at converting electricity into light? How do you know?

41. Energy Efficient Light Bulbs… • How are they made? How it’s Made: Fluorescent Bulbs How it’s Made: Incandescent Bulbs NatGeo energy efficient bulbs

42. Device efficiency is expressed as a percentage (%) • To determine the efficiency of a device: • An incandescent light bulb converts 200 J of electricity into 25J of light. What is the efficiency of the bulb?

43. An electric kettle uses 240 000J to heat water. 196 000J is actually used to heat the water. What is the efficiency of the kettle?

44. Using energy efficient devices will benefit: • Electrical bills by saving money • Environmental by using fewer fossil fuels

45. Chapter 7.1 – Energy for Life • Plants convert the Sun’s solar into chemical potential energy stored in glucose (sugar) • This is done through the process of photosynthesis  solar  chemical potential

46. Animals convert the chemical potential energy in plant and animal cells into mechanical energy • This is done through the process of cellular respiration  chemical potential  mechanical

47. Animals can get energy from eating plants or from eating other animals • Energy stored in the cells of plants and animals is transferred through the food chain

48. Only 10% of energy is transferred to the next level as it moves through an food chain • This is demonstrated by an energy pyramid • Less and less energy is available at each level in a food chain • Fewer organisms can be supported with each level

49. 7.2 – The Need for Energy • Our bodies area able to maintain a constant temperature through the process of homeostasis • If your body temperature drops: • Shivering burns sugar and produces heat • Blood is sent to core of the body to preserve heat • If your body temperature rises: • Blood is sent to skin to release extra heat to air • Perspiration transfers heat energy to the air

50. The rate at which the body uses energy is called metabolism • A person with a high metabolism: • has high energy needs • converts a lot of chemical energy into heat energy • A person with a low metabolism has low energy needs • has low energy needs