Conduction: It is the method in which the transfer of heat takes place between atoms and molecules in direct contact.
Convection: It is the method in which the transfer of heat happens by the movement of the heated substance.
Radiation: It is the method in which the transfer of heat takes place by electromagnetic waves.
Classification of Heat
Heat can be classified as follows:
- Hot
- Cold
Hot
Objects with high heat content are defined as hot (Hotness or coolness of an object is a relative term is always measured with respect to a reference object).
Examples of hot objects around us include the sun, fire, hot pans, air from a hairdryer, lava from volcanic eruptions, etc.
Cold
Objects with lower heat content are defined as cold objects. Hotness or coolness of an object is a relative term that is always measured with respect to a reference object.
Examples of cold objects around us include ice, air from an air conditioner, cold drinks, metal vessels kept in open on cold winter days etc.
Sources of Heat
There are many sources of heat but the following are the main sources of heat:
- Sun
- Chemical
- Electrical
- Nuclear