Ch # 08 Transmission of heat Flashcards
(21 cards)
Define thermal energy ?
The kinetic energy of particles in matter is called thermal energy.
In which direction heat flows?
Heat flows from an object at higher temperature
to an object at lower temperature.
Define transmission of heat?
The transfer of heat energy from one object to the other is called transmission of heat.
Define conduction?
The transfer of heat through matter without the actual movement of particles from their position is called conduction.
Define bad conductor?
Materials which do not allow heat to flow through them easily are called bad conductors
Bad conductors also called?
Heat insulators
Define good conductor?
Materials which allow heat to flow through
them easily are called good conductors of heat.
Define molecules?
All solids (metals and non-metals) are made of tiny particles called molecules.
How heat energy is transferred in metals?
In metals, heat energy is transferred from one
place to another both by the vibrations of particles as well as by the movement of free electrons.
Why the process of conduction in liquids and gasses is slow than solids(metals) ?
The process of conduction in liquids and gases is very slow as compared to solids (metals). The particles in liquids and gases are not held closely together.
Hint used in Everyday Applications of Conduction of Heat?
Bibi put
Hint used in Everyday Applications of Conduction of Heat?
Bibi put
_Birds feathers
_Ice is covered with jute rugs
_Blankets and woolen clothes slow down transfer of heat
_Insulating material is filled between the double
walls of a refrigerator.
_double-PAN windows are used
_cooking UTENSILS
_Thermos bottles
Define convection?
The transfer of heat in which molecules of a medium actually
move to the source of heat energy to absorb heat and then
move away from it, is called convection.
Define convection current?
The upward and downward movement of molecules of water or
air is called a convection current.
Why convection is not possible in solids?
Convection occurs in liquids and gases only because their
molecules can move freely. The molecules of a solid are held
closely together. They cannot move freely, therefore, convection
is not possible in solids.
What is advantage of gliding flight of bird?
They enjoy gliding. During gliding flight a bird does not move its wings, but glides on air currents. A lot of energy of birds is saved during gliding.
List the Everyday Applications of Convection Currents?
Household ventilation
Domestic water heater
Air conditioner
Define radiation?
The transfer of heat energy from a hot body to a cold body directly, without heating the space in between the two bodies is called radiation.
Why black surface is a Good absorber and good radiator?
Because black surface absorb most of the radiations.
Hint of Everyday Applications of Radiation of Heat?
Fsc P(Pakistan)
Fire
Summer days
Cooling fins
Plastics
Hint of Vaccum flask?
Carpals Mat
Container
Air between glass walls
Reduce the rate of transfer of heat
Protected glass bottle by fixing it in a metal
Amount of heat is lost by conduction
Lost by conduction
Silvered and smooth glass walls prevent transfer of heat
Metal bottles
Aluminium on the vacuum side
Three ways transfer of heat.
