How do temperature changes create convection currents?

Answer 1

When they get hotter, gasses and fluids have a lower density (they weigh less per cubic inch) so they rise above the cooler material.

Another answer

Most of the time a convection current happens within the Earth, in the layer which we call the mantle. Like the rock cycle, it has no certain beginning. Heated material becomes less dense. As it becomes less dense, it rises to the surface. At the surface, it cools, which causes it to become more dense, and that causes it to sink. It gets heated, and the process starts all over again.

Answer 2

Convection is the flow of heat (or mass) through a bulk, macroscopic movement of the atoms and/or molecules of a fluid from a hot region to a cool region, as opposed to the microscopic transfer of heat between atoms and/or molecules involved with conduction. Convection occurs in fluids.

Suppose we consider heating up a local region of air. As this air heats, the molecules spread out, causing this region to become less dense than the surrounding, unheated air. The heated, less dense air will rise and will be replaced by cooler, more dense air due to buoyant forces. This movement of hot air into a cooler region is then said to transfer heat by convection.

Heating a pot of water on a stove is a good example of the transfer of heat by convection in a liquid. When the stove is first turned on heat is transferred first by conduction between the element through the bottom of the pot to the water. However, eventually the water molecules adjacent to the botttom get hotter than the surrounding water molecules. They are less dense, and rise from the bottom to be replaced by cooler, more dense molecules. This is the transfer of heat from the hot water at the bottom to the cooler water at the top by convection. Convection currents will be set up and heat will be transferred throughout the water in the pot.p

In summary, convection currents are responsible for the movement of heat (and mass) within a fluid system.

Heat wants to go from where it is to where it isn't. When atoms and or molecules of a fluid (a gas or liquid, for example) are hotter then their companion particles, they are less dense and rise in the fluid. Cooler, more dense groups of atoms or molecules take their place. Convection currents are thus set up, and heat travels "around" the system via those currents.

A link to the Wikipedia article on convection is provided.

A:

Convection currents occur when a fluid is in contact with a heat source. They are a method of heat transfer that is exploited in our own homes as radiators use this effect to heat our homes.

Cold air for example will come in contact with the radiator and become heated up. This warm air is less dense than cold air so it rises upwards towards the ceiling. From here it spreads out across the room and sinks as it begins to cool down. From here the cycle starts again.

Answer 3

Ocean currents result from two processes - the action of wind on the surface of the water, and from variation in water temperature that causes movement- a process known as convection. Convection occurs because the oceanic waters heat up becoming less dense.

Answer 4

As temperature changes, the density of air changes. With changes in density you get pressure gradients, which produce movements of large masses of air. In this respect, it is "convection." Think of it as horizontal convection.

The other, more obvious instance is the bouancy effect of warmer, less dense air in cooler, denser air. Like a less dense cork in denser water, the less dense air rises - i.e. convection occurs. In contrast with the first example this is more vertical convection. The convection can result either from air at the bottom getting warmed up - or- air at the top getting cooled off and sinking while the warmer air below rises.

Of course the two effects can combine to cause convection to move more or less in any direction.

Obstacle to air flow can also redirect the air and make the convection more chaotic and intersecting convection currents can further scramble the direction of flow.

Answer 5

When a fluid (such as air or water) is heated, it expands and becomes less dense, causing it to rise. As it rises, it cools and becomes denser, then sinks. This movement of fluid due to temperature changes creates convection currents.