Now you’ve found the final piece of the circuit puzzle:  resistance (Ω). When you put it together with the other three concepts you learned about in this lesson, you have the four basic principles you need in order to study electronics.

The Four Principals

• Charge, a measure of the accumulation of negatively-charged subatomic particles called electrons. Charge is measured in coulombs, and is abbreviated as C.
• Current, which is the amount of charge (the number of electrons) moving past any point in a circuit in a given amount of time. It is measured in amperes, which are usually called “amps,” and abbreviated as A.
• Voltage is the force pushing electrons through a circuit.  You can think of it as the amount of “pressure” moving an electron in a circuit, and it is measured in volts, abbreviated as V.
• Resistance, which is pretty much what it sounds like:  the tendency for any component of a circuit to try to keep electric current from flowing through that component.  Resistance is measured in ohms, and it is abbreviated with the Greek letter omega, Ω.

In the next sections, we’ll explore how these concepts interact in an electric circuit, because they have a very specific relationship that helps us manage electricity to do useful work, and keep us safe at the same time.