Current Flow is the flow rate of electrons. One ampere of current is a flow rate of 6,250,000,000,000,000,000 electrons per second. As you can see, this is a very large number and the ampere (amp) is a large unit of measure. We normally use the "milli" or even "micro" multipliers to scale down this large unit.

There are two ways of referring to the flow of current: Electron versus Conventional. Don't get this confused!

• Electron flow (technically correct) specifies that current flows OUT of the NEGATIVE terminal of a power supply- through the circuit- back to the POSITIVE power supply terminal. This is really what happens. The negative terminal of a power supply has a SURPLUS of electrons, and the POSITIVE terminal has an electron deficiency. When a power supply is connected to a circuit, lost of "free" electrons flow from NEGATIVE power supply terminal - through the circuit- back to the POSITIVE terminal (electrons are attracted to the positively-charged atoms lacking electrons - opposite charges attract).

• CONVENTIONAL current flow is the opposite to that described above. POSITIVE - to - NEGATIVE flow. We will use CONVENTIONAL current flow because it is the most popular model, and the solid-state electronic symbols you will learn in ENT 178, 180, 281 all use arrows to denote conventional flow direction.