Let a spherical block of ice at -7 °C be exposed to atmospheric air at 30 °C with the gravitational direction as shown in the figure below. What will be the overall direction of air flow in this situation?
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When dealing with temperature-induced air movement, remember that hot air rises and cold air sinks due to differences in density.
Step 1: Understanding the situation.
The spherical block of ice is at a lower temperature (-7°C), while the surrounding air is at a higher temperature (30°C). This creates a temperature gradient between the block and the surrounding air. Step 2: Air behavior due to temperature difference.
Since the ice block is colder than the surrounding air, the cold air near the ice block is denser than the warmer air. According to the principles of fluid mechanics and thermodynamics, cold air is heavier and tends to sink, while warm air is lighter and rises. Step 3: Convection effect.
This difference in temperature and density between the cold air near the ice block and the surrounding warmer air creates a convection current. The cooler air near the block will sink due to its higher density, while the warmer air will rise. Step 4: Overall air flow direction.
Since the cold air sinks, the overall direction of air flow near the ice block will be downward. Therefore, the correct answer is (B) downward.
