Bell Ringer 4-9-10

1. Bell Ringer 4-9-10 • What is kinetic energy? • What is potential energy? • What SI unit measures energy? • Do you think energy can be lost during a transfer of energy? Explain.

2. Chapter 13 Section 3Energy Transformations

3. Energy Transformation • Most forms of energy can be transformed into other forms. • A change from one form to another is calledenergy transformation.

4. Single Transformations • Toaster - electrical energy  thermal energy (to toast your bread) • Cell phone - electrical energy  electromagnetic energy (that travels to other phones) • Human body - chemical energy in your food  mechanical energy you need to move your muscles and  thermal energy to maintain body temperature

5. More Examples • A steam iron __________ energy __________ energy • A ceiling fan __________ energy __________ energy and ___________ energy • A hair dryer __________ energy __________ energy and ___________ energy

6. Multiple Transformations • The mechanical energy used to strike a match is transformed first to thermal energy. • The thermal energy causes the particles in the match to release stored chemical energy, which is transformed to thermal energy. • The light that you see is electromagnetic energy.

7. Another Example • In a car, electrical energy produces a spark. • The thermal energy of the spark releases chemical energy in the fuel. • The fuel’s chemical energy in turn becomes thermal energy. • Thermal energy is converted to mechanical energy to move the car and electrical energy to produce more sparks.

8. Another Example • Using coal to power a generator: Chemical Energy is converted to heat energy (steam) which is converted to mechanical energy (turns blades of turbine) to electrical energy and then back to heat energy (using a toaster at home).

9. One of the most common transformations is between potential and kinetic energy. • Potential Energy  Kinetic Energy

10. Examples of Potential  Kinetic 1. Juggling

11. 2. Pendulum

12. 3. Pole Vault

13. The law of conservation of energy states that when one form of energy is transformed to another, no energy is destroyed in the process. Energy cannot be created or destroyed. Total Amount of energy is constant!!!! Conservation of Energy

14. Energy Efficiency • Energy efficiency is how much useful energy you can get out of a system. • In theory, a 100% energy-efficient machine would change all of the energy put in it into useful work.

15. Examples of Efficiency • The human body is less than 5% efficient….most energy is transferred to heat energy. • An incandescent light bulb converts 10% of electrical energy into light and the rest is converted into thermal energy. • Electrical Power plants are about 35% efficient.

16. Heat • During these transformations some energy may be released in the form of heat (friction). • No machine is 100% efficient because friction transforms mechanical energy to thermal energy.