How is heat energy transferred?

Question

Nora Arzate · Accepted Answer

There are three ways that heat can be transferred: conduction, convection, and radiation.

As in the case of a metallic strip, conduction is the transfer of heat from one heated side to the other through the constituent particles, which then supply the heat to the adjacent particles. Eventually, the other end of the strip heats up as well, and heat transfer ceases completely when the two ends reach thermal equilibrium.

When we heat a saucepan of water on the stove, the water at the bottom heats up first, and eventually we find the entire water is boiling, not just the bottom part. This is known as convection. It is observed that in conduction, there is no movement of particles from their mean positions. However, in the case of fluids, when one side gets heated, the particles heat up and start moving faster, colliding with others and allowing colder particles to take up heat.

Since constituent particles are involved in the previous two methods of heat transfer, it follows naturally that a material medium must exist for conduction and convection to occur. However, since the universe is known to be a free space (vacuum), we are still unsure of how the sun's heat gets to us.

To explain this, we have to understand that the sun (and other stars as well) emit Electromagnetic radiation which are oscillating electric and magnetic fields propagating through space. They don't necessarily need a material medium. You might be familiar from your studies on electricity and magnetism that an electric field and a magnetic field store energy of energy densities #(epsilon""_0E^2)/2# and #B^2/(2mu""_0)# respectively . So, you've got your answer, radiation carries energy without the need of a material medium in form of electromagnetic fields. This is how, the sun's heat reaches us.

Lily Adams · Answer

undefined Heat energy is transferred through three main processes: conduction, convection, and radiation.

1. Conduction: Heat transfer by conduction occurs when two objects at different temperatures are in direct contact with each other. Heat energy flows from the object with higher temperature to the object with lower temperature, causing the particles in the cooler object to gain kinetic energy and increase in temperature.

2. Convection: Convection involves the transfer of heat energy through the movement of fluids (liquids or gases). As the fluid is heated, it becomes less dense and rises, while cooler, denser fluid sinks. This creates a circular motion known as convection currents, which transfer heat from one place to another.

3. Radiation: Radiation is the transfer of heat energy through electromagnetic waves. Unlike conduction and convection, radiation does not require a medium and can occur through empty space. Heat from the sun reaching the Earth is an example of radiation, as is the warmth felt from a fire or a hot object.