ENERGY TRANSFORMATIONS…

1. ENERGY TRANSFORMATIONS… - Satinder Virdi

2. Specific Expectations D3.1 describe a variety of energy transfers and transformations, and explain them using the law of conservation of energy D3.2 explain the concepts of and interrelationships between energy, work, and power, and identify and describe their related units D3.3 explain the following concepts, giving examples of each, and identify their related units: thermal energy, kinetic energy, gravitational potential energy, heat, specific heat capacity, specific latent heat, power, and efficiency

3. Introduction to the topic Work, work, work. You might head off to your job one day, sit at a computer, and type away at the keys. That's all we do here. Is that work? To a physicist, only parts of it are. Sitting and looking at a computer screen is not work. Tapping on the keyboard and making the keys move is work. Your fingers are applying a force and moving the keys. Driving to your job is not work because you just sit, but the energy your car engine uses to move the car does work. You have to exert a force AND move something to qualify as doing work.

4. Lesson Sequence • Work done • Concept of energy • Different types of energy • Inter-conversion between different energy forms • Law of conservation of energy

5. Pre-requisites • Concept of Displacement, Acceleration • Scalars and Vectors • Concept of Force • Newton’s Laws of motion • Resolution of vectors

6. Work Done Work is done when a force that is applied to an object moves that object in the direction of the force. Then, work done is calculated by multiplying the force by the amount of movement of an object Mathematically: (W = F * d).

7. Describing Work Mathematically • W = f*d*cosΘ • Force and displacement are rightward. Hence the work done is positive. • Force left, displacement right. Hence the work done is negative. • Force up, displacement left. Hence the work done is zero.

8. Work Done or not ? • A teacher applies a force to a wall and becomes exhausted. • A book falls off a table and free falls to the ground. • A waiter carries a tray full of meals above his head by one arm across the room. • A rocket accelerates through space.

9. Answers • No. The wall is not displaced. • Yes! There is a downward force (gravity) which acts on the book to displace it. • No. There is an upward force, and there is a horizontal displacement but the force does not cause the displacement • Yes the expelled gas is the force (thrust) which accelerates the rocket through space.

10. Energy We use the concept of energy to help us describe how and why things behave the way they do. We talk about solar energy, nuclear energy, electrical energy, chemical energy, etc. If you apply a force to an object, you may change its energy. That energy must be used to do work, or accelerate, an object. Energy is called a scalar; there is no direction to energy (as opposed to vectors). We also speak of kinetic energy, potential energy, and energy in springs. Scientists measure energy in units called joules.

11. Active Energy vs. Stored Energy Kinetic and potential energies are found in all objects. If an object is moving, it is said to have kinetic energy (KE). Potential energy (PE) is energy that is "stored" because of the position and/or arrangement of the object.

12. Kinetic Energy Kinetic energy exists whenever an object which has mass is in motion with some velocity. Everything you see moving about has kinetic energy Kinetic Energy Lab

13. Potential Energy Potential energy is described as the energy stored by an object due to its position or condition. Potential Energy Lab

14. Thermal Energy Thermal energy is the internal energy in substances - the vibration and movement of atoms and molecules within substance.

15. Specific Heat Capacity The specific heat capacity of a substance is the amount of energy that must be added to raise 1.0 kg of the substance by 1.0 K. The SI unit used to measure it is J/Kg/K Heat Capacity The heat capacity of a substance is the amount of energy that must be added to raise given mass of the substance by 1.0 K. The SI unit used to measure it is J/K Latent Heat Also known as Hidden Heat, it is the amount of heat required to change the state of the unit mass of a substance, with out rise in temperature. The SI unit used to measure it is J/Kg

16. Power Power is the rate at which work is done. Since work is defined as a transfer of energy, power can also be defined as the rate at which energy is transferred.

17. Efficiency The efficiency of a machine or device describes the extent to which it converts input energy or work into the intended type of output energy or work.

18. Law of conservation of energy Law of Conservation of Energy :- Energy can neither be created nor destroyed. Energy is always changing from one kind to another. The total energy of an object never changes. • http://www.youtube.com/watch?v=jid7Nlzfet8

19. Some misconceptions • Force = energy • The presence of energy enables the body to exert force and hence equivalent amount of work is performed. • Energy is only in living things • Even non-living things have energy, fossil fuel is a simple example. • Energy can be made, used and lost • One form of energy gets converted in the other form, while performing work, but nothing gets lost if all the energy forms are considered together.

20. Accommodation for special needs students and English Language Learners Following accommodations will be made: • providing additional time to complete tests or assignments • permitting oral responses • computer options and use of technology • preferential sitting as outlined in their Individual Education Plans (IEPs). Gifted students can be challenged to complete extensions of topics covered in class to their everyday lives such as using green alternatives for chemicals • extensive use of visual clues such as - graphic organizers, pre-teaching vocabulary, pre-viewing text books, peer tutoring, using a variety of learning resources such as bi-lingual dictionaries and simplified texts.

21. Project • Draw a flow map showing the flow of energy transformations in a car from starting vehicle to driving. You should have 5 different types of energy.

22. Expected Solution: Sound (mechanical) Electrical Thermal Mechanical Electrical Chemical Electrical Light (Electromagnetic)

23. Assessment & Evaluation • Quiz on conservation of energy • Simulation Lab – Kinetic and Potential Energy Labs • Project - Rubric forthe project and oral presentations (Communication, Application) • Unit Test (Knowledge/Understanding, Application, and Communication) with emphasis on Application of the concepts learned.

24. Practical Application • Wind power energy path • Water power energy path

25. Some useful Internet Sites Work-Energy simulation lab worksheet : • http://romano.physics.wisc.edu/winokur/fall2007/EnergySimulations.pdf Build a coaster • http://www.learner.org/interactives/parkphysics/ Concept simulation – Illustrates the relationship between kinetic and potential energy • Potential and Kinetic Energy Experiment For Law of conservation of energy (Newton’s Cradle): • http://www.youtube.com/watch?v=jid7Nlzfet8 • http://www.youtube.com/watch?feature=player_detailpage&v=51RCyBr_nGk