Tips & Tricks
Answering Difficult Electrical Questions
by: Vince Fischelli (CEO, Veejer Enterprises, INC.)
I began working in the automotive service industry in 1968 after 10 years in military electronics. The last ve of those years I was teaching electronics. My new civilian job had me repairing the new emerging technology of AM-FM stereo radios for new cars. Part of my job was to answer tech-line questions from dealership technicians with electrical problems. As the new technician I had to answer all tech-line calls “to pay my dues.” Piece of cake I thought, no problem. Boy was I wrong.
One of the rst calls I got (remember it is 1968) was a technician who said: “Help! I have voltage feeding back into ground. What do I do?” He was connecting a blower motor ground wire to the chassis producing a large electrical spark as soon as the “hot” blower motor ground wire connected the chassis. In his mind he had voltage feeding back into ground. In my mind, I had no idea how voltage could feed back into ground. That was a new concept to me. What was happening of course, the technician was repairing a broken ground wire with the circuit powered ON. If he had simply turned OFF the ignition key before connecting the ground wire, there would have been no spark.
Well, let the games on the phone begin and they did. Confusing calls like this continued to make me question the likelihood of success in my rst new civilian job. I eventually realized that it was poor or no electrical training in the automobile industry that generated confusing electrical questions I never encountered in military classes. Military students had already attended basic electrical school before my classes, and their questions were based on sound electrical principles and easy to answer. I had no ready answer for confusing questions from auto technicians.
As I began to teach electrical troubleshooting classes in the vehicle service industry, I realized confusing electrical questions resulted from technicians being confused about the concepts of voltage and electron current in a circuit. Knowledgeable students keep the two concepts separate and ask easy questions about each that have an answer.
Here is the solution to understanding confusing electrical questions. You cannot answer a voltage question with an answer about electron current. You cannot answer an electron current question with an answer about voltage. ASK THE STUDENT IF THEIR QUESTION IS ABOUT THE VOLTAGE IN THE CIRCUIT OR THE ELECTRON CURRENT FLOWING THROUGH THE CIRCUIT. Then watch their blank stare as you have just explained to them the reason for their confusion. Once they clarify, if they can, their question is either about voltage in a circuit or electron current flowing through a circuit, is a correct answer possible and their confusion vanishes. The sooner the better you explain the difference between voltage and electron current in every circuit you present, the sooner the student understands.
To illustrate, the figure on the facing page is a simple circuit. Circuit A shows the switch in the OFF position. There is no electron current so the lamp (load) is OFF or OUT. Take a moment to describe the component parts of a circuit, the circuit symbols used and the wires connecting the component parts to complete the circuit. Discuss the voltage source (called B+) is present but the circuit doesn’t work until the switch is CLOSED because there is no electron current through the circuit.
In Circuit B the switch is CLOSED and electron current flows from the negative terminal of the voltage source, B-, through the load and CLOSED contacts of the switch and ultimately arrive at B+, the positive terminal of the voltage source.
This simple circuit illustration explains the fundamental truth of any circuit. If sufficient electron current flows through a circuit, the load operates or “works.” Now the door is open to discuss what happens in a circuit when the electric current is missing or too low. Voltage and electron current are two different parameters in a circuit. Voltage is measured in volts and electron current is measured in amperes, or amps for short. The question can only be a voltage question of a current question. Keep them separate.