describe the process of convection
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Convection is the circular motion that happens when warmer air or liquid — which has faster moving molecules, making it less dense — rises, while the cooler air or liquid drops down. ... Convection currents within the earth move layers of magma, and convection in the ocean creates currents.
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Convection is the process of moving heat around by putting it into the molecules of a gas or liquid and then moving that hot gas or liquid to a new place where the heat can be released. Convection occurs naturally in our weather systems. If you sit by a large body of water on a sunny summer day you may notice later in the day a breeze coming off the water towards land (on-shore breeze). This is caused when the sun has had time to heat up the land, which in turn heats up the air in contact with it. This hot air expands and rises because it is less dense. As the warm air rises, the cooler air over the water rushes in to replace the warm rising air (the breeze you feel) and the warm air migrates up and over the lake, where it cools and settles down onto the lake. There you have a complete cycle of air flow that moves heat away from the land and spreads it out to cooler locations.
Convection can occur in very large scale. Hurricanes occur because hot tropical ocean water heats the air and makes it rise, thus starting the cycle. The winds of the hurricane is simply the cooler air rushing from the surrounding high pressure areas in to replace the hot rising air in the middle (low pressure because the air is less dense and rising). Convection can also occur in small scales too. Your oven distributes heat by convection as air touches the hot elements and then rises up and the cooler air drops down and moves in to replace it. Of course, convection is only one method of moving heat around. The other major methods are conduction and radiation. Condiction is where the heat passes through a material without making the molecules move to a new location. The hot molecules vibrate faster than their neighbors and they bump into them which makes them move more (get hotter). Also infrared radiation moves heat. Feel the warmth of a fireplace from across the room. That's infrared radiation. It can even pass through glass, like the glass fire doors in front of the fireplace that would totally prevent heat from transferring out by convection.
Convection can also occur artificially. A forced-air furnace heats the air and then uses a fan to pump it throughout the house through the hot air ducts to all the rooms where the hot air can then release the heat to warm up all parts of the house. Notice the cold air returns are always located low in the walls or the floors and bring the cooler air back to the furnace so it can be heated again. When I was a child, furnaces didn't use forced air and the heat was convected through the house passively via open grates in the floors and ceilings and just by having an open house. This was most effective in smaller multi story houses where the heat could rise up to the upper floor rooms. The outer rooms were always colder in winter as the heat had a long way to go to reach them. That's why older houses centered on the kitchen where heat from the wood stove could spread more easily to the living room, dining room and even beds, if they were all open to the one central space. We wore fuzzy jammies, night caps and lots of blankets on our beds to stay warm.
Convection can occur in very large scale. Hurricanes occur because hot tropical ocean water heats the air and makes it rise, thus starting the cycle. The winds of the hurricane is simply the cooler air rushing from the surrounding high pressure areas in to replace the hot rising air in the middle (low pressure because the air is less dense and rising). Convection can also occur in small scales too. Your oven distributes heat by convection as air touches the hot elements and then rises up and the cooler air drops down and moves in to replace it. Of course, convection is only one method of moving heat around. The other major methods are conduction and radiation. Condiction is where the heat passes through a material without making the molecules move to a new location. The hot molecules vibrate faster than their neighbors and they bump into them which makes them move more (get hotter). Also infrared radiation moves heat. Feel the warmth of a fireplace from across the room. That's infrared radiation. It can even pass through glass, like the glass fire doors in front of the fireplace that would totally prevent heat from transferring out by convection.
Convection can also occur artificially. A forced-air furnace heats the air and then uses a fan to pump it throughout the house through the hot air ducts to all the rooms where the hot air can then release the heat to warm up all parts of the house. Notice the cold air returns are always located low in the walls or the floors and bring the cooler air back to the furnace so it can be heated again. When I was a child, furnaces didn't use forced air and the heat was convected through the house passively via open grates in the floors and ceilings and just by having an open house. This was most effective in smaller multi story houses where the heat could rise up to the upper floor rooms. The outer rooms were always colder in winter as the heat had a long way to go to reach them. That's why older houses centered on the kitchen where heat from the wood stove could spread more easily to the living room, dining room and even beds, if they were all open to the one central space. We wore fuzzy jammies, night caps and lots of blankets on our beds to stay warm.
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