2. HEAT
HEAT is energy (thermal) in transit, energy that
transfers from one body to another because of
temperature difference.
Heat flows from an area of high temperature to an
area of low temperature (unless an external work is
done).
Heat is measured with the following SI units:
joules (J); calorie (cal); kilocalorie (kcal or Cal)
where: 1 cal = 4.184J and 1 Cal = 1000cal
3. SOURCES OF HEAT
A. NATURAL SOURCES
1. the Sun
2. interior of the Earth
B. ARTIFICIAL SOURCES
1. chemical action
2. mechanical energy
3. electrical energy
4. nuclear energy
4. THERMAL ENERGY AND TEMPERATURE
THERMAL ENERGY
- also called Internal Energy
- the total energy in a system or body; the sum
of kinetic and potential energy of the atoms or
molecules of a body
TEMPERATURE
- measure of the degree of hotness or
coldness of a body
- the average kinetic energy of the molecules
of a body
12. METHODS OF HEAT TRANSFER
1. CONDUCTION – heat transfer through solids
*Thermal conductivity – ability of a material to allow
heat to pass through
* Kinds of material based on thermal conductivity:
a. conductors – allow heat to pass through
b. insulators – resist heat transfer
2. CONVECTION – heat transfer through fluids (liquids and
gases), which involves currents/flow
3. RADIATION – heat transfer through empty space,
through electromagnetic radiation, such as light,
microwave, etc.
