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Potentiometers
18 questions By Tony R. Kuphaldt
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Question 7 of 18
Draw a schematic diagram showing a potentiometer being used as a simple variable resistor for varying current to a light bulb. Also, designate which way the “wiper” should be moved to make the bulb glow brighter.
Reveal answer
Notes:Make note of the fact that only two of the potentiometer’s three terminals need be used if a simple variable resistor is desired.
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Question 8 of 18
What is the difference between the following potentiometers, as indicated by their respective symbols?
Reveal answerThe symbol on the left belongs to a standard, knob-adjustable potentiometer. The symbol on the right belongs to a “trimpot,” which is a potentiometer adjustable only by a screwdriver, intended for non-routine adjustments.
Notes:Ahhh, the joy of symbols! Do not be surprised if students are able to dredge up all kinds of electronic component symbols from symbol libraries you’ve never seen before.
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Question 9 of 18
What would you expect the voltmeter in the following circuit to do when the potentiometer wiper is moved to the right?
What would you expect the voltmeter to register if the wiper were set precisely at the 50% (half-way) position?
Reveal answerAs the wiper is moved to the right, we should expect to see the voltmeter register an increasing voltage, ranging between 0 and 12 volts DC.
Follow-up question: a useful problem-solving method is to imagine multiple “test case” scenarios, sometimes referred to as thought experiments, for the purpose of identifying a trend. For instance, in this circuit you might imagine what the voltmeter would register with the wiper moved all the way to the left, and then with the wiper moved all the way to the right. Identify the voltmeter’s readings in these two scenarios, and then explain why the analysis of “test cases” like these are useful in problem-solving.
Notes:Ask your students to describe possible applications for a circuit like this. Where might we wish to utilize a potentiometer in such a way that it outputs a variable voltage, from a constant voltage source?
