Discussion of the section on convection and radiation

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You can bake potatoes in a conventional oven, or in a microwave oven. Baking potatoes in the oven takes "40 minutes to an hour, depending on their size" in a 425o F oven, while in a microwave, the length of time to cook depends on how many potatoes you are trying to cook: 4 minutes for one, 8 minutes for 2, ... , a half-hour for 8. The two ways to cook a potato differ in many respects; please note that the dials set different things.

Q1: Explain why a microwave oven cooks a potato faster than a conventional oven.


Q2: Explain why it takes twice as long to cook two potatoes as one potato, in a microwave, and yet the time in a conventional oven is the same for one or more.

Q3: When my Uncle David roasts potatoes in the oven, he turns them over half-way through. If he doesn't, they get burned on the bottom. Which method of transport of thermal energy causes the burning?

Conduction     
Convection     
Radiation     
Change of phase     

Q4: On some nights, the grass gets cold and dew or frost forms on it. What process of transfer of thermal energy is most responsible for making the grass cold?

Conduction     
Convection     
Radiation     
Change of phase     

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