Grade 11 - Resistance (Thermal Systems)

PRESCRIBED LEARNING OUTCOMES

• identify factors causing resistance to heat flow in a thermal system
• describe the advantages and disadvantages of resistance in a thermal system
• identify methods used to reduce and increase thermal resistance
• describe R-value as used to indicate the relative insulating value of materials
• discuss the relationship between the transfer of thermal energy and the type and physical dimensions of material through which it is transferred
• describe the relationship between thermal resistance, temperature difference, and rate of heat flow in a thermal system
• calculate the thermal resistance of a material, using values for:
• temperature
• heat flow rate
• thickness
• cross-sectional area
• thermal conductivity

SUGGESTED INSTRUCTIONAL STRATEGIES

• As a class activity, have students fill two containers, one insulated and one uninsulated, with hot water. Ask them to place a thermometer in the centre of each container and record the temperatures at 2-minute intervals over a 20-minute period. Have students plot temperature versus time for the two containers on the same graph. Lead a class discussion on the effect of insulation on the transfer of thermal energy.
• Ask students to bring in a variety of insulated coffee cups and compare the effectiveness of their insulation.
• Invite an expert on energy insulation in the home to present information about insulation and conservation. Ensure that the advantages and disadvantages of various insulating methods are covered. Have students develop recommendations to improve the efficiency of their homes or selected buildings.
• Provide thermal imaging photos showing houses with different levels of insulation and ask students to interpret them. Discuss the interpretations, emphasizing specifics about conservation of energy.

SUGGESTED ASSESSMENT STRATEGIES

• As students calculate thermal resistance from given values, look for evidence that they are able to:
  • identify variables
  • predict the effect of modifying variables
  • use appropriate units and terminology
• Have students design home heating systems that maximize heat transfer from source to location of use. In assessing their projects, look for evidence that students are able to:
  • create feasible designs
  • select efficient energy sources
  • consider a variety of factors in designing their systems (e.g., R-value, temperature difference, thickness, cross-sectional area, thermal conductivity)
  • correctly perform appropriate calculations
• Form groups and ask each to make a poster presentation of a heat collector designed to minimize heat waste. Assessment criteria might include:
  • calculation of potential heat loss
  • appropriate application of thermal resistance, temperature resistance, and flow rate
  • organization and quality of presentation
  • simplicity and feasibility of design
• Have students respond in their journals to prompts such as:
  • One way to improve thermal transfer is _________________ .
  • A difficulty in making calculations in real-world applications is _________________ .
  • The advice I would give someone analysing thermal transfer problems is _________________ .
  • One question I have about resistance and thermal transfer is _________________ .

RECOMMENDED LEARNING RESOURCES

Applications of Physics 11 and 12 develops an understanding of the concepts of physics through the design, construction, and use of a variety of devices. Although the resources listed below provide a range of teaching and learning opportunities in physics, none of them provide a comprehensive resources package that completely supports the philosophy and approach of the British Columbia curriculum in the applications of physics. Please see the Appendix B Introduction for further information.

Print Materials

• 75 Easy Physics Demonstrations
• Cambridge Coordinated Science: Physics
• Heinemann Advanced Science: Physics
• Physics: Principles and Problems, American Edition
• Physics: Principles and Problems, Canadian Edition

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Last Modified: April 1, 1998.
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