# 1 With a partner next to you identify

• Slides: 15

1. With a partner next to you, identify 3 examples of Conduction, Convection, and Radiation (total 9 examples) not discussed in class. 2. Describe your observations of the heat transfer in each example. 3. Describe what is causing the heat transfer in each example. U 3 g – L 2

March 23, 2010 DRILL Answer the following in your notebook: 1. What is a more scientifically correct way of saying “the ice cubes made my water cold”? 2. Identify the methods of heat transfer expressed in the pictures/diagrams below: Convection Radiation Conduction U 3 g – L 3

TEST FRIDAY – Unit 3 F and Unit 3 G (Fluid and Thermal Technology) U 3 g – L 2

• • Thermal energy always travels from a region of higher temperature to a region of lower temperature. Therefore, the driving force for heat transfer is Difference in Temperature • Three methods of heat transfer: 1. Conduction 2. Convection 3. Radiation U 3 g – L 2

1. Conduction The transfer of heat through a substance by collision of molecules. • Conduction happens through solids. • Metals are usually best conductors. • Free electrons greatly aid in the transfer of thermal energy. • Fluids are less conductive of heat due to larger distances between atoms. U 3 g – L 2

1. Conduction U 3 g – L 2

2. Convection The transfer of heat by movement of a fluid. • Natural Convection – Fluid surrounding a heat source receives heat and rises (due to lower density) – Surrounding cooler fluid moves in to replace it. – Cooler fluid is heated, rises, and cycle continues. U 3 g - L 1

2. Convection • Forced Convection – Fans or other means are used to propel a fluid. – An convection current is induced. – Car engine and A/C are examples U 3 g – L 2

3. Radiation The transfer of heat by electromagnetic waves • • All objects, hot or cold, emit heat by radiation No medium is necessary – radiation works in a perfect vacuum (the sun’s heat through space) Light contains heat radiation The visible spectrum carries less heat than the infrared spectrum U 3 g – L 2

3. Radiation U 3 g - L 1

Is it Conduction, Convection, or Radiation? 1. Warm water rises in a lake. Cold water descends. Convection 2. The sun transfers its heat to our planet through space. Radiation 3. A thermometer under your tongue shows that you have a high fever. Conduction 4. On cloudless nights, heat escapes from our planet and goes into space. Radiation U 3 g – L 3

5. You place a spoon into a cup of cocoa and it gets hot over time. Conduction 6. A thermos bottle has a shiny interior. What type of heat transfer does it prevent? Radiation 7. Heat in the room moves with the warm currents from warmer areas to cooler areas. Convection 8. Brownies bake in a glass pan using these 2 methods. Radiation (from oven) and Conduction (through pan) 9. You feel the heat of a wood stove when you stand U 3 g – L 3 next to it. Radiation and Convection

TEST FRIDAY – Unit 3 F and Unit 3 G (Fluid and Thermal Technology) U 3 g – L 2

1. Identify 5 thermal technologies not mentioned in class today • (Remember, a thermal technology produces, stores, controls, transmits or gets work from heat energy) 2. Identify the problem that the technology system solves 3. List the technological subsystems that are used in the technology 4. Identify the technology that preceded it (i. e. what was used before the technology was invented? ) U 3 g – L 2

1. Complete the Fluid and Thermal Technology Test Review sheet. 2. What you don’t finish in class, you must finish for homework. 3. LETTER all answers. U 3 g – L 3