IB Physics SL B 1 10 Thermal Transfer Mechanisms Questions
Practise conduction, convection and radiation using insulation, surfaces, fluids and planetary energy pathways in exam questions.
- Syllabus
- First assessment 2025
- Course
- Physics SL
- Level
- SL
Practise conduction, convection and radiation using insulation, surfaces, fluids and planetary energy pathways in exam questions.
An electrically heated pad is designed to keep a pet warm.
The pad is heated using a resistor that is placed inside the pad. The dimensions of the resistor are shown on the diagram. The resistor has a resistance of 4.2Ω and a total length of 1.25 m .
When there is a current in the resistor, the temperature in the pad changes from a room temperature of 20∘C to its operating temperature at 35∘C.
The design of the pad encloses the resistor in a material that traps air. The design also places the resistor close to the top surface of the pad.
Explain, with reference to thermal energy transfer, why the pad is designed in this way.
Air is a poor «thermal» conductor
Lack of convection due to air not being able to move in material
Appropriate statement about energy transfer between the pet, the resistor and surroundings
The rate of thermal energy transfer to the top surface is greater than the bottom «due to thinner material»
Marking guidance:
Accept air is a good insulator
3 max