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Basic Circuit Troubleshooting
18 questions By Tony R. Kuphaldt
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Question 7 of 18
Suppose this battery and light bulb circuit failed to work. Using nothing but a voltmeter, how would you check the circuit to determine where the problem is located? Note: the letters indicate “test points” along the wiring where you may probe with the circuit with your voltmeter.
Reveal answerThere are several strategies which may be employed to find the location of the problem in this circuit. One popular technique is to “divide the circuit in half” by testing for voltage between points C and H first. The presence of absence of voltage between these two points will indicate whether the problem lies between those points and the battery, or between those points and the light bulb (assuming there is but a single problem in the circuit - a large assumption!).
Notes:A circuit like this is very easy to construct, and makes for an excellent classroom demonstration piece. I’ve used such a circuit, constructed on a piece of pegboard 2 feet by 4 feet, with metal screws acting as test points, for students to develop their troubleshooting skills in front of the class where everyone may observe and learn together.
It has been my experience that students who experience difficulty troubleshooting circuits in general usually experience difficulty troubleshooting this simple circuit in particular. Although the circuit itself couldn’t be simpler, the fundamental concept of voltage as a quantity measurable only between 2 points is confusing for many. Spending lots of time learning to troubleshoot a circuit such as this will be greatly beneficial in the future!
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Question 8 of 18
Suppose this battery and light bulb circuit failed to work:
Using a voltmeter, a technician measures full battery voltage between the points C and H. What does this single measurement indicate about the condition of the circuit? Be as specific as you can.
Reveal answerBased on this one measurement, we are able to determine that the battery is outputting full voltage, and that the circuit wiring is continuous from the negative battery terminal to point C, and from the positive battery terminal to point H. The fault is an öpen” somewhere to the right of points C and H - possibly more than one.
Notes:Some measurements given definite answers, while others only indefinite answers. In this particular question, the single voltage measurement tells us definite things about the left-hand side of the circuit, but little about the right-hand side. It is very important for students to develop the logical skill of distinguishing necessary conclusions from possible conclusions in troubleshooting scenarios. A skill like this takes time and practice to develop, so be sure to spend adequate time throughout the course with your students honing it!
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Question 9 of 18
Suppose this battery and light bulb circuit failed to work:
Using a voltmeter, a technician measures full battery voltage between the points C and H. The result of this single measurement indicates which half of the circuit there is a definite problem in. What would you recommend as the next voltmeter measurement to take in troubleshooting the circuit, following the same “divide in half” strategy?
Reveal answerTo “divide the circuit in half” again, measure voltage between points D and I.
Notes:Some troubleshooters refer to this strategy as “divide and conquer,” because it divides the possibilities of fault location by a factor of 2 with each step. Make sure your students understand that being able to immediately determine which part of a system is not faulted is a valuable time-saver.
May I know the people who created these examples? through APA 6 or 7 format of citation?
Some good brain teasers. It was nice getting my head wrapped around the idea of getting voltage on a common side of a circuit (due to a break on that side) 🤠