Fig. 1 shows three roof panels being tested for a satellite. Panel A is dull black, panel B is matt white and panel C is shiny silver. Each panel contains a...
Question 1 Report
Fig. 1 shows three roof panels being tested for a satellite. Panel A is dull black, panel B is matt white and panel C is shiny silver. Each panel contains an identical electric heater. In space, energy can leave the panels only by radiation because there is no air around the satellite.
(a) Which panel is the best emitter of thermal radiation? [1]
(b) What colour and surface should be used for a panel that must lose energy slowly? [1]
(c) Explain why conduction cannot transfer energy from a satellite panel into space. [2]
Fig. 1 shows a bowl of cooked rice being reheated in a microwave oven. The centre of the bowl is cooler than the outside when the oven stops. A student covers the bowl, leaves it for two minutes, and then measures the temperature at several positions. Energy continues to move through the food after the microwave source is switched off.
(a) What type of waves transfer energy from the oven source to the food? [1]
(b) Describe why energy moves from the hotter outside of the rice to its cooler centre after heating. [2]
(c) Give one reason why the student should stir the rice before eating it. [1]
Answer Details
Satellite roof panels
- (a) Panel A, the dull black panel, is the best emitter of thermal radiation. [1] Dull black surfaces are good emitters, whereas shiny surfaces are poor emitters.
- (b) A panel intended to lose energy slowly should have a shiny silver, or light shiny, surface. [1]
- (c) Conduction needs particles to transfer energy by collisions. [1] Space is a vacuum and has no particles, so conduction from the panel into space cannot occur. [1]
Reheated rice
- (a) The oven source transfers energy to the food using microwaves. [1]
- (b) There is a temperature difference between the hotter outside and cooler centre. [1] Thermal energy is transferred by conduction from hotter regions to cooler regions. [1]
- (c) Stirring makes the temperature more even, reducing the risk of burns from hot regions and helping ensure all the food is hot. Any one of these is acceptable. [1]
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