Thermal Processes

Vacuum is NOT air!!

Convection Toy – Angels Carousel

This simple toy is made possible using convection current in the air.

The ‘fan’ of the carousel is similar to the windmill we are familiar with.  Just that the kinetic energy of the wind is created by the stream of hot air rising up from the bottom. It is the opposite of an electric fan.

Processes for Transfer of Thermal Energy

Three processes of thermal transfer: conduction, convection and radiation.

Conduction vs Convection:

Similarity:

• both requires a medium for thermal transfer to take place.

Differences:

• convection cannot take place in solid but conduction can.
• conduction is due to vibration and collision of molecules while convection is due to fluid density changes.

Radiation vs Conduction & Convection

• Radiation can take place in vacuum but both conduction and convection require a medium.

Convection Current – demo

Convection is a process in which thermal energy is transferred within a fluid (liquid or gas) due to the difference in density which creates a current.

The video below shows the convection current in a heated tube filled with water. Colour dye is added to enable us to see the convection current through our naked eyes.