(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.
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