Methods of heat transfer Flashcards
Why do objects transfer heat?
If two objects with two different temperatures meet, then they need to reach a thermal equilibrium. The thermal energy from the object with the higher temp flows into the object with lower temp, till the 2 objects have the same temp., attaining thermal equilibrium.
What are the methods of heat transfer?
- Conduction - any heat which you feel from contact
- Convection - any heat moving upwards
- Radiation any heat you feel from afar
Explain conduction
In solids, conduction is very efficient. When two solids meet, they want to reach a thermal equilibrium. The particles of the warmer solid start to vibrate, and then the particles next to those particles vibrate. In a solid, the particles are very closely packed together, so thermal energy is easily transferred. Once the other solid reached the same temp, they stop transferring energy.
Explain convection.
- A heat source heats up fluid materials which are closest to the heat source. As these materials have a high temperature, they have more KE, which means they are moving away from each other. This results in them having less density
- As that part of the fluid has less density than other parts, the lighter part will rise, and the denser part will sink to be heated up.
- This creates a cycle known as a convection cycle.
How does a beaker heat up?
- The heat from the heat source heats up the beaker
- The beaker heat up the few water molecules in contact via conduction
- As the water molecules, heat up, the kinetic energy increases and density lowers at that area, as the particles move away from each other.
- However, the other parts of the water have a higher density, so they sink
- The water with lower density rises and the water with high density sinks and gets heated
- This happens till a thermal equilibrium is achieved.
- This process is known as a ‘convection cycle.’
Explain radiation.
- Radiation is a type of electromagnetic ray which is carried in the form of energy waves. It is the infrared section of the electromagnetic rays
- The sensation of radiation for a human being is how cold or hot the object is
- Just like any other energy transfer, radiation move from a high thermal energy zone to a low thermal energy zone. Hence, this can be termed as a method of heat transfer as well.