Convection occurs when heat is transferred through a gas or liquid by the hotter material moving into a cooler area. Discover what convection really is and review several examples of this phenomenon.
It’s important to understand convection’s definition before considering examples, so you’re clear on what convection really is. Convection is a transfer of heat related to the movement that occurs within a fluid due to the rising of hotter materials paired with the sinking of colder materials. This occurs because hotter materials have less density than colder ones.
In meteorology, convection is the transfer of heat and other atmospheric properties by the movement of masses of air, particularly in an upward direction. In geology, it is the slow movement of material below the Earth's crust. Some convection is manmade.
There are numerous examples of convection in everyday life, including several common household occurrences.
- boiling water - When water boils, the heat passes from the burner into the pot, heating the water at the bottom. This hot water rises and cooler water moves down to replace it, causing a circular motion.
- radiator - A radiator puts warm air out at the top and draws in cooler air at the bottom.
- steaming cup of hot tea - The steam you see when drinking a cup of hot tea indicates that heat is being transferred into the air.
- ice melting - Ice melts because heat moves to the ice from the air. As a result, the ice melts from a solid to liquid.
- frozen food thawing - Frozen food thaws more quickly under cold running water than if it is placed in water. This is because the action of the running water transfers heat into the food faster than if the frozen item was placed in still water.
- forced convection - When a fan, pump or suction device is used to facilitate convection, the result is forced convection. Everyday examples of this can be seen with air conditioning, central heating, a car radiator using fluid, or a convection oven.
Many weather conditions are the result of convection. From a meteorology perspective, convection is just an upward motion of air in the atmosphere. This sounds simple enough, but it can lead to severe weather in certain conditions.
- convective clouds - When the air has a lot of moisture, the convection currents will carry that moisture up into the sky to form convective clouds. When droplets build up in the clouds sufficiently, the result will be precipitation in the form of a convective thunderstorm.
- squall lines - A squall line is a type of convective thunderstorm. This type of convective event produces a line of thunderstorms accompanied by high wind and blowing rain.
- supercell - A supercell is a more severe form of a convective thunderstorm. This type of storm typically lasts for an extended period of time (an hour or longer) and has a high chance of forming dangerous tornadoes.
While less commonly observed than everyday examples of convection that happen at home and weather phenomena, there are a number of other examples of convection associated with air movement.
- hot air balloon - A heater inside a hot air balloon heats the air, causing the air to move upward. This causes the balloon to rise because the hot air gets trapped inside. When the pilot wants to descend, the individual will release some of the hot air. Cool air takes its place, causing the balloon to lower.
- the stack effect - Also referred to as the chimney effect, the stack effect is the movement of air in and out of buildings, flues or other objects because of buoyancy. In this case, buoyancy refers to the different densities in the air between air inside and the air outside. The buoyancy force increases due to the greater height of the structure and a greater difference between heat level of the inside and outside air.
While the impact of geological convection isn’t something that people can observe in real time, it greatly affects the natural world. A number of natural phenomena are related to convection related to geology.
- mantle convection - The rocky mantle of the Earth moves slowly because of the convection currents that transfer heat from the interior of the Earth up to the surface. This is the reason the tectonic plates move gradually around the Earth. Hot material is added at the growing edges of a plate and then it cools. At the consumption edges, material becomes dense by contracting from the heat and sinks into the Earth at an ocean trench. This triggers the formation of volcanoes.
- gravitational convection - Because fresh water is buoyant in salt water, dry salt diffuses downward into wet soil. This is an example of gravitational convection.
- oceanic circulation - Convection causes the oceans to continually circulate globally. Warm water around the equator circulates towards the poles and the cooler water at the poles moves towards the equator.
While stars are not below the earth’s surface, you can also see the principles of convection at play when considering convection associated with stars, which can also be referred to as stellar convection. A star has a convection zone where energy is moved by convection. Outside the core is a radiation zone where plasma moves. A convection current forms when the plasma rises and the cooled plasma descends.
These different examples of convection show how convection occurs throughout many human-made and natural occurrences. Now that you are familiar with examples of convection, consider expanding your knowledge of related scientific phenomena. Start by exploring ten condensation examples common in real life.