Basic Electricity

Simple Circuits

41 questions By Tony R. Kuphaldt

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Question 19 of 41

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 answer

Based 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 “open” 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!
Question 20 of 41

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 answer

To “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.
Question 21 of 41

Suppose this battery and light bulb circuit failed to work:

Using a voltmeter, a technician measures 0 volts 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 answer

Based on this one measurement, we are able to determine that there is definitely a problem in the circuit somewhere on the left-hand side (from points C and H, left). The exact nature of the problem is unknown, but there is definitely a problem of some nature in that half of the circuit.

There may or may not be a problem on the right-hand side of the circuit, as well. Given this single voltage measurement, we simply cannot tell.

Notes:
There are times when a voltmeter indication of 0 volts is just as informative concerning a circuit fault as a non-zero measurement. In this case, the measurement tells us that a definite problem exists in one half of the circuit.