P2 - Energy Transfer By Heating Flashcards
Conduction
One way heat moves from place to place in solids, heat is carried through vibrations
In insulators (non-metals), it is only caused by passing vibrations from atom to atom
Conduction in a solid
A solid is heated up
The free electrons from the metal absorb heat energy, making them move faster (heat energy to kinetic energy)
The free electrons collide into metal ions, causing vibrations
Some of the kinetic energy of the free electron is absorbed by the ions, vibrating faster
Convection
When heat is transferred in liquids and gases
Convection in a liquid
Heat is initially transferred through conduction
The water in the region of the heat source is heated
It expands, becomes less dense, and rises, replaced by the cooler denser water that surrounds it
The water in turn is heated, expands becomes less dense, and rises
This process continues and a convection current is set up and heat is transferred through the liquid
Convection in a gas
Air close to the source is heated
It expands, becomes less dense, and rises; replaced by the cooler denser air that surrounds it
The air in turn is heated, expands becomes less dense, and rises
The process continues and a convection current is set up and heat is transferred through the air
Infrared radiation
Electromagnetic radiation, when radiation is absorbed by an object it is heated, and its temperature rises
Radiation can work through the vacuum of space
Specific heat capacity (SHC)
The quantity of energy needed to raise the temperature of a 1kg object by 1°C
Specific heat capacity formula
Change in thermal energy / mass x temperature change
ΔJ / m x ΔT
M = mass (kilogram, kg)
ΔJ = change in thermal energy (joules, J)
ΔT = temperature change (celsius, °C)
U-value
A measure of heat loss, the higher the u-value the more the insulation loses heat
