Basic Electrical Theory
Generally, electric current flow can be classified as one of two general types: Direct Current
(DC) or Alternating Current (AC). A direct current flows continuously in the same direction.
An alternating current periodically reverses direction. We will be studying DC and AC current
in more detail later in this text. An example of DC current is that current obtained from a
battery. An example of AC current is common household current.
Real and Ideal Sources
An ideal source is a theoretical concept of an electric current or voltage supply (such as a
battery) that has no losses and is a perfect voltage or current supply. Ideal sources are used for
analytical purposes only since they cannot occur in nature.
A real source is a real life current or voltage supply that has some losses associated with it.
The important information contained in this chapter is summarized below.
Conductor - material with electrons loosely bound to its atoms or that permits
free motion of large number of electrons
Insulator - material with electrons tightly bound to its atoms; requires large
amounts of energy to free electrons from its nuclei
Resistor - material that conducts electricity, but opposes current flow
Electron Current Flow - current flow from negative to positive potentials
Conventional Current Flow - current flow from positive to negative potentials
Direct Current - current flow continuously in the same direction
Alternating Current - current flow periodically reverses direction
Ideal Source - theoretical current or voltage supply with no losses
Real Source - actual current or voltage supply with losses