Page 1 - Lesson Notes- Convection

SAI INTERNTIONAL SCHOOL
Class 7
Lesson Notes
Subject- Physics
Ch- Heat and Temperature
Subtopic- Convection

Convection:

Convection is the process of transfer of heat in which heat is transferred in
fluids through the actual movement of particles.

• Heat transfer in liquids and gases takes place through convection.
• This method of transfer of heat takes place in liquid and gases only as
their particles are loosely packed and free to move.
• Sea breeze and Land breeze are the example of convection currents.

Applications of Convection:

• Air conditioners are installed near the ceiling of the room because they
release cool air into the room. As cool air is denser, it sinks while the
warm air present in the room being less dense rises and move towards
the ceiling. Which again gets cooled by the AC. This process continues
and results in effective cooling of the room.
• Exhaust fans are fitted near the ceiling of the kitchen. They ensure the
escape of hot air and gases that rises up as hot air is lighter .
• Room heaters are placed on the floor of a room, this results in effective
heating of the room. As cool air being denser settles near the floor
which then heated by the room heater.
• Formation of sea breeze and land breeze is due to convection.

Activity:

Observing Convection Currents in Water

Aim:
To observe how heat is transferred through liquids by convection.

Materials Required:

• A transparent glass or beaker
• Water
• Potassium permanganate crystals (or food coloring)
• Candle or spirit