(1) Alternating current. The AC generator produces alternating

current which is unacceptable for automotive systems. The alternator rust have

a rectifier installed to convert AC to DC to satisfy the needs of the storage

battery. In the alternator, the magnetic field is rotated and voltage is

produced in the stationary coils. One advantage of the AC generator is that it

will produce current at low speeds which make it the more acceptable component.

(2) Direct current. The DC generator, as its name implies, produces

DC current, but must be run at a much higher speed than the AC generator. The

DC generator works much the same way as the AC generator, but the magnetic

field is stationary and coils of wire, called an armature, are rotated in the

magnetic field. A magnetic switch, brushes, and a commutator are provided.

3. Ohm's Law states that the voltage impressed on a circuit is equal to the

sum of the product of current measured in ohms. One ohm is the resistance of a

circuit element that permits a steady current of one ampere to flow when a

steady force of one volt is applied to the current. An easy way to remember

Ohm's Law is to think of a triangle with E at the top and I and R in the lower

angles (Figure 12).

E = Volts, I = Current in Amperes, R = Resistance in Ohms

Figure 12. Ohm's Law Triangle.