When two objects in the vicinity of each other have different electrical charges, an electrostatic field exists between them. An electrostatic field also forms around any single object that is electrically charged with respect to its environment. An object is negatively charged (-) if it has an excess of electrons relative to its surroundings. An object is positively charged (+) if it is deficient in electrons with respect to its surroundings.


The phase change of liquid water into water vapor. This is the process whereby atoms or molecules in a liquid state gain sufficient energy to enter the gaseous state. It is the opposite process of condensation.

Evaporator Coil

A series of metal tubes similar to a radiator in an automobile. Evaporators are used to change the state of refrigerant from a liquid to a cold low pressure gas.

Expansion Tube

A small diameter tube connecting the condenser coil and evaporator coil which facilitates the refrigerants change of state from a liquid to a gas.