In last month's article, I covered the basic fundamentals of electricity (see Archives pages at, and will continue and conclude with Circuits and Magnetism.

KINDS OF CIRCUITS:  1. Simple circuit:  In a simple circuit, current flows from the battery through a lamp and back to the battery, to complete the circuit.

2. Series Circuit:  In a series circuit, two or more lamps are connected.  The important thing to know is that in this circuit there is only one path for current flow.  An example of a series circuit is the headlight switch to the headlights, because the electricity goes through the switch before the headlights.  Voltage drop in a series circuit:  This is simply the difference between the voltage at one point in a circuit and the voltage at another point in the same circuit.

3. Parallel Circuit:  This is where the lamps are connected so that there is more than one path for the current to flow.  Part of the current flows through one lamp and part of it through the other lamp, so if one bulb burns out, the other continues to operate because the circuit is not completely broken.  A break in the main conductor will stop the current flow in that part of the circuit.  An example of a parallel circuit would be headlights and tail lights.

4. Ground Circuit:  On vehicles, we use a combination of basic and parallel circuits with one main difference.  Instead of running separate return wires from the components back to the battery, the body, engine and frame are used as common return conductors.  This is referred to as the vehicle ground circuit.  On our cars, it is important to make sure all parts are connected to the ground circuit.  Body, engine and frame should all be connected with ground straps.  If a strap is loose, it could show up in a radio noise, but like our '64 Corvette, the tal lights had a low glow.


        Without magnetism, electrical energy would have few practical applications.  It is essential to the operation of a generator, alternator, coil and starter.  The simplest type of magnet is a permanent bar magnet.  Lines of force leave the magnet at the north pole and enter again at the south pole.  The magnetic field is all of the space outside of the magnet, containing lines of magnetic force.  When a bar magnet is bent into a horse shoe shape, the magnetic field becomes stronger because of the reduction in the distance from north and south poles.


Unlike poles attract, like poles repel

Magnetic lines of force pass through all materials

Magnetic lines pass easily through materials that can be magnetized, like steel or iron, and less easily through air or across an air gap.

Permanent magnets employ hard steel alloys because they retain magnetic strength when they are magnetized.


Magnetic lines of force are created around the wire when a current flows through the wire.  These lines of force are concentric circles formed around the wire.  They have no polarity and no north or south pole.  An Electromagnet is formed, having a north and south pole, by forming a wire into a loop and sending and electric current through the wire.  Lines of force will form around the wire, but now each circular line of force leaves at one side of the wire loop and enters the other side.  Thus, the lines of force all pass through the center of the wire loop, creating the electromagnet.  The more turns of wire, the more lines of magnetic force and the stronger the electromagnet.  Increasing the amount of current flowing in the windings of the electromagnet increases its strength.

An automotive alternator, for example, operates as a pulley turned by a blet connected to the automobile engine's crankshaft, spins a magnet past a stationary set of windings called the stator.  The spinning magnet is actually an eletromagnet.  Alternators are designed this way so that the magnetic field strength can be controlled, in order that output voltage may be controlled independently of rotor speed.  This rotor magnet coil (called the field) is energized by battery power, so that it takes a small amount of electrical power input to the alternator to get it to generate a lot of output power.  

These are some basic automotive electrical fundamentals. Writing this article has helped me to learn a little more about the subject, and I hope it helps you as well, to have a greater understanding of our cars' electrical systems.  Keep 'em driving!