本题目来源于试卷: gc textbook chater 14 heat，类别为 IB物理学
[问答题]
Does an ordinary electric fan cool t yabnkqn57 e 0 iqfl(c05w/of:he air? Whyv y8ypnu/ys ;: or why not? If not, why use it?
参考答案:
An ordinary fan does not cool the air
directly. It actually warms the air
slightly, because the motor used to power the fan will exhaust some heat into
the air, and the increase in average kinetic energy of the air molecules caused
by the fan blades pushing them means the air temperature increases
slightly. The reason for using the fan
is that it keeps air moving. The human
body warms the air immediately around it, assuming the air is initially cooler
than the body. If that warmed air stays
in contact with the body, then the body will lose little further heat after the
air is warmed. The fan, by circulating
the air, removes the heated air from close to the body and replaces it with
cooler air. Likewise, the body is also
cooled by evaporation of water from the skin.
As the relative humidity of the air close to the body increases, less
water can be evaporated, and cooling by evaporation is decreased. The fan, by circulating the air, removes the
humid air from close to the body and replaces it with less humid air, so that
evaporation can continue.
本题详细解析:
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