Electricity is the flow of electrons from one place to another. Electrons can flow through any material, but does so more easily in some than in others. How easily it flows is called resistance. The resistance of a material is measured in Ohms.
Matter can be broken down into:
- Conductors: electrons flow easily. Low resistance.
- Semi-conductors: electron can be made to flow under certain circumstances. Variable resistance according to formulation and circuit conditions.
- Insulator: electrons flow with great difficulty. High resistance.
Since electrons are very small, as a practical matter they are usually measured in very large numbers. A Coulomb is 6.24 x 1018 electrons. However, electricians are mostly interested in electrons in motion. The flow of electrons is called current, and is measured in AMPS. One amp is equal to a flow of one coulomb per second through a wire.
Making electrons flow through a resistance requires an attractive force to pull them. This force, called Electro-Motive Force or EMF, is measured in volts. A Volt is the force required to push 1 Amp through 1 Ohm of resistance.
As electrons flow through a resistance, it performs a certain amount of work. It may be in the form of heat or a magnetic field or motion, but it does something. This work is called Power, and is measured in Watts. One Watt is equal to the work performed by 1 Amp pushed by 1 Volt through a resistance.
AMPS is amount of electricity.
VOLTS is the Push, not the amount.
OHMS slows the flow.
WATTS is how much gets done.