How are convection currents formed in the air?

Answer 1

Simple Answer:

Warm air rises during convection. Perhaps better said, natural convection of air is the rising of less-dense warm air relative to the more-dense cold air.

This is a simple matter of buoyancy. Gravity pulls everything downward, but the pull is proportional to mass and items immersed in a fluid that have lower mass per unit volume than the fluid will tend to float, i.e. experience a buoyant force up as gravity pulls harder downward on the surrounding fluid.

Causes and Explanation:

Everyone says "Warm air rises" and that is an example of natural convection. Convection requires a fluid, heat source and gravity. The heat source causes a temperature gradient in the fluid so that buoyancy of the warmer fluid causes it to rise.

Buoyancy is the reasons bubbles rise and hot air balloons float and anything light, like a piece of wood, raises to the surface. The gravitational force experienced by a volume of material is just its weight, i.e. mass times gravity. Mass is the density of the material times its volume. So, if the object (like wood) has a lower density than water, the force of gravity on the object is less than the equivalent volume of water. The buoyant (upward) force is the difference in the wight of the object and the weight of the same volume of liquid.

Light objects experience the upward buoyant force and if the fluid (air or water or any fluid) is heated and expands, then it has a larger volume and less density and it also experiences the upward force.

The natural buoyancy of warmer fluids causes the force that moves the fluid and that movement is what we call natural convection.

Other Aspects:

1. Convection is why we say "heat rises." And, an interesting side observation is that when water cools near the freezing point, it actually gets lighter as the temperature drops from 4 C to 0 C, hence causing the cooler water in that range to be less dense and more buoyant.
2. There is also something called forced convection where fluid is moved by artificial means such as air pushed by a fan. Most home heating occurs with "forced convection" but years ago natural convection resulting from buoyancy of hat air was the cause for air circulation.
3. Convection is a main driver of our weather, but locally and globally. Surface air warmed when the sun sticks the Earth and is changed to heat which gets absorbed by the air. Surface air tends to rise and takes surface moisture with it. If there is enough of the moisture, it comes back as rain somewhere else. Globally, the oceans give up most of the moisture we later experience as rain and the warmest area of the planet, near the equator, produces large scale convection of air that is essential to global weather patterns.

Answer 2

Hot air rises because it is lighter and cold air is more dense and falls but the higher air goes, the colder it gets because the air above it is cold so it falls back down again and this keeps happening so you get convection currents - geddit?

Answer 3

The general circulation of a heated sphere is for air to rise at the warm equatorial regions as it is less dense, and in the polar regions where the sun angle is low and air is cool it sinks (more dense). Thus a circulation is set up. But the earth is much more complex as the earth rotates air parcels which move from high to low pressure tend to turn to the right. This is due to Coriolis force. Motion of air near the surface is further complicated by friction, mountains, and land sea interfaces.

But if you really want to dig deeper, air flow tends to conserve what is called potential temperature, and will flow on these isentropic surfaces. When saturation is reached motion flows on saturation potential temperature surfaces.

Convection results when air parcels are less dense than the air around them. They flow upward, expand and cool conserving potential temperature until saturation is attained. Then as long as the parcels are less dense than the air around them they ascend conserving the saturation (or wet bulb) potential temperature. Motion only slows down when they reach an environment that is less dense or warmer than the parcels. The parcel gradually stops in a damping sinusoidal motion. Sometimes this occurs with thunderstorms in the stratosphere.

Answer 4

Simple Answer:

Warm air rises during convection. Perhaps better said, natural convection of air is the rising of less-dense warm air relative to the more-dense cold air.

This is a simple matter of buoyancy. Gravity pulls everything downward, but the pull is proportional to mass and items immersed in a fluid that have lower mass per unit volume than the fluid will tend to float, i.e. experience a buoyant force up as gravity pulls harder downward on the surrounding fluid.

Causes and Explanation:

Everyone says "Warm air rises" and that is an example of natural convection. Convection requires a fluid, heat source and gravity. The heat source causes a temperature gradient in the fluid so that buoyancy of the warmer fluid causes it to rise.

Buoyancy is the reasons bubbles rise and hot air balloons float and anything light, like a piece of wood, raises to the surface. The gravitational force experienced by a volume of material is just its weight, i.e. mass times gravity. Mass is the density of the material times its volume. So, if the object (like wood) has a lower density than water, the force of gravity on the object is less than the equivalent volume of water. The buoyant (upward) force is the difference in the wight of the object and the weight of the same volume of liquid.

Light objects experience the upward buoyant force and if the fluid (air or water or any fluid) is heated and expands, then it has a larger volume and less density and it also experiences the upward force.

The natural buoyancy of warmer fluids causes the force that moves the fluid and that movement is what we call natural convection.

Other Aspects:

1. Convection is why we say "heat rises." And, an interesting side observation is that when water cools near the freezing point, it actually gets lighter as the temperature drops from 4 C to 0 C, hence causing the cooler water in that range to be less dense and more buoyant.
2. There is also something called forced convection where fluid is moved by artificial means such as air pushed by a fan. Most home heating occurs with "forced convection" but years ago natural convection resulting from buoyancy of hat air was the cause for air circulation.
3. Convection is a main driver of our weather, but locally and globally. Surface air warmed when the sun sticks the Earth and is changed to heat which gets absorbed by the air. Surface air tends to rise and takes surface moisture with it. If there is enough of the moisture, it comes back as rain somewhere else. Globally, the oceans give up most of the moisture we later experience as rain and the warmest area of the planet, near the equator, produces large scale convection of air that is essential to global weather patterns.

Answer 5

the air above the candle flame gets hot and expands. The hot air becomes less dense and rises vertically out of the chimney.cooler air is then drawn intothe box through the outer chimney to replace the hot air which has escaped .The movements of the hot and cold air set up a convection current .The smoke produced by a piece of smouldering paper held above the cooler chimney makes the convection current visible.

Answer 6

It is simply that hot air is of less density and it moves upwards bringing cold air as replacement. This cold air when warmed up it flows upwards and bringing cold air again in replacement. Accordingly the convection current occurs.

Answer 7

simple diagram showing convection in liquid

Answer 8

Convection is when less dense, warm air rises. The buoyancy of hot or warm air that has risen results in air currents.

Answer 9

???????????????????????????????????????...………...………...………………………..Confused