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Voltage Divider Circuits
37 questions By Tony R. Kuphaldt
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Question 16 of 37
When the 5 kΩ potentiometer in this circuit is set to its 0%, 25%, 50%, 75%, and 100% positions, the following output voltages are obtained (measured with respect to ground, of course):
- At 0% setting, Vout = 0 V
- At 25% setting, Vout = 2.5 V
- At 50% setting, Vout = 5 V
- At 75% setting, Vout = 7.5 V
- At 100% setting, Vout = 10 V
Calculate what the output voltages will be if a 1 kΩ load resistor is connected between the “Vout” terminal and ground:
- At 0% setting, Vout =
- At 25% setting, Vout =
- At 50% setting, Vout =
- At 75% setting, Vout =
- At 100% setting, Vout =
Reveal answer- At 0% setting, Vout = 0 V
- At 25% setting, Vout = 1.29 V
- At 50% setting, Vout = 2.22 V
- At 75% setting, Vout = 3.87 V
- At 100% setting, Vout = 10 V
Notes:This question is really nothing more than five loaded voltage divider problems packed into one! It is a very practical question, as potentiometers are very often used as variable voltage dividers, and students must realize the effects a load resistance will have on the characteristics of such dividers. Point out to them the extreme nonlinearity created by the inclusion of the load resistance.
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Question 17 of 37
Determine the voltages (with respect to ground) at points A and B in this circuit under four different conditions: both loads off, load 1 on (only), load 2 on (only), and both loads on:
Voltage Both loads off Load 1 on (only) Load 2 on (only) Both loads on
VA
VB
Reveal answer
Voltage Both loads off Load 1 on (only) Load 2 on (only) Both loads on
VA 26.4 volts 26.3 volts 22.4 volts 22.3 volts
VB 5 volts 4.46 volts 4.23 volts 3.78 volts
Notes:Students will have to re-consider (and possible re-draw) the circuit for each loading condition, which is one of the major points of this question. The fact that a circuit can “change” just by throwing a switch is an important concept for electronics students to grasp.
Another concept employed in this question is that of voltages specified at single points with an implied reference of ground. Note to students how each voltage was simply referenced by a single letter, either A or B. Of course there is no such thing as voltage at a single point in any circuit, so we need another point to reference, and that point is ground. This is very commonly seen in electronic circuits of all types, and is a good thing to be exposed to early on in one’s electronics education.
A much less obvious point of this question is to subtly introduce the concept of discrete states (loading conditions) available with a given number of boolean elements (switches). Given two load switches, there are four possible states of circuit loading, previewing binary states in digital circuits.
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Question 18 of 37
Calculate both the total resistance of this voltage divider circuit (as “seen” from the perspective of the 25 volt source) and its output voltage (as measured from the Vout terminal to ground):
Note that all potentiometers in this circuit are set exactly to mid-position (50%, or m = 0.5).
Reveal answerRtotal = 9.762 kΩ
Vout = -12.5 V
Notes:Ask your students to explain why the output voltage is expressed as a negative quantity. Is this important, or is it an inconsequential detail that may be omitted if desired?
Also, it might be good to ask your students to show the equivalent circuit (made up entirely of fixed resistors) that they drew in route to solving for total resistance and output voltage. Encourage them to take this step if they have not already, for although it does involve “extra” work, it helps greatly in keeping track of the series-parallel relationships and all calculated circuit values.
Plus signs are missing from these questions and answers, such as in question 11, where the denominator of the voltage divider equation appears as “R1 R2 R3” instead of “R1+R2+R3”. Same in the answer to question 15. Likely elsewhere as well, as Find shows no results for “+” anywhere on the page. I’m using Chrome 88.0.4324.182 on Windows 10, but same on Firefox & Edge. HTML source for the page shows it as “R1 R2 R3”, so it isn’t just a display problem.
Iam a student and i need an explain for this answers how can I get an explanation ?
Ca any one tell in detail how
The formula got formed like this !! ( ER= Et(R/Rt)) thank you