Heat Transfer
1. Conduction - Heat transferred from warmer to cooler areas in solid objects.
In the oven, the metal tray
heats up and helps transfer
heat to the biscuits. Metal is
a good conductor.
Heat moves from the burner to
the pot. Most pots have plastic
handles. Wood and plastic are
not good conductors. They are
called insulators.
Heat from the hot drink
moves to the mug.
2. Convection - Heat transferred through currents in liquids or gases.
Warm gas or liquid rises.
Cooler gas or liquid sinks.
The movement of the liquid
or gas is called a convection
current.
The air, which is a gas, is heated
right in front of the heater.
Warm air is lighter than cool
air, so it rises. Cool air comes
down to take its place. This
then gets warmed and rises.
A fish tank heater heats
water. Heat moves in a
circular motion.
3. Radiation - Heat transferred through infrared rays.
Radiation is the spreading out of heat rays. We feel heat from the Sun as it
travels to the Earth by infrared rays.
All objects give out and take in thermal radiation, which is also called infrared
radiation. The hotter an object is, the more infrared radiation it emits.
We feel heat from
a light bulb as it
radiates heat into the
surrounding air.
A fire is an example of radiant heat.
No particles are involved in the process
of radiation, unlike conduction and
convection. Radiation can even work
in space.