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Convective flow should be family to anyone who has noted the boiling
of a heated liquid. The most elementary type of convection can be
explained by the fact that heat rises. In the simplest cases, convective
flow begins when a fluid is heated, it expands and thus become less
5 dense than the layers above. The warmer and lighter bottom layer
then tends to rise and the cooler layer tends to sink in a continuous
cycle. The same mechanism of convective flow is responsible for the
great ocean currents and for the global circulation of the atmosphere.
In an ocean, the water is warmed by the Sun to a depth of perhaps
10 thirty meters, and evaporation near the water's surface is responsible
for the cooling effect.
1. The main purpose of this passage is to
2. According to the passage, what happens as a fluid is warmed ?
3. What does the passage say about ocean currents ?
4. According to the passage, which of the following is the result of convective flow ?
5. A simple example of convection could be seen in
Xem lại bài Reading-Comprehension-Lesson 86 và bài Reading-Comprehension-Lesson 85
