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Kirchhoff’s Laws
48 questions By Tony R. Kuphaldt
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Question 25 of 48
Use Kirchhoff’s Voltage Law to calculate the magnitude and polarity of the voltage across resistor R4 in this resistor network:
Reveal answer
Notes:In your discussion, be sure to explore more than one “loop” when using KVL. Not only does this demonstrate the arbitrary nature of your loop choice, but it also serves as a double-check for your work!
It is not necessary to know anything about series-parallel or even parallel circuits in order to solve the R4‘s voltage - all one needs to know is how to use Kirchhoff’s Voltage Law.
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Question 26 of 48
A very old but highly accurate technique for measuring voltage is to use a sensitive meter (a galvanometer) as a “balance” indicator between two voltage sources: the unknown source and a calibrated, adjustable source called the standard:
The technique is to adjust the standard voltage source until the galvanometer registers exactly zero. When this condition is met, the system is said to be “balanced,” indicating that the two voltage sources are equal in magnitude to each other. This voltage magnitude is then read from the calibrated adjustment dial on the standard source.
Explain how this voltage measurement technique exploits Kirchhoff’s Voltage Law, which states that the algebraic sum of all voltages in a loop must equal zero:
EΣ(loop) = 0 Reveal answerI’ll leave the answer for you to demonstrate!
Notes:Potentiometric voltage measurement is not only practical, but for quite a while in the early field of electrical measurements it was the only way to accurately measure voltage from “weak” (high-impedance) sources. It is still used today in electrical metrology, and serves as a simple application of KVL for students to examine.
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Question 27 of 48
Calculate the amount of voltage between test points TP1 and TP3, and also the amount of voltage between test points TP2 and TP4:
VTP1−TP3 = VTP2−TP4 =
Reveal answerVTP1−TP3 = 15.83 volts VTP2−TP4 = 22.22 volts
Notes:Ask your students to explain how they obtained their answers. There is more than one correct way to answer this question!
I think there is a mistake in question 28 more specifically step 3 and 4. I think their answers are switched. Step 3 should be 12 and Step 4 should be -24
In the notes for question 4, the diagram should have a 47k resistor, not 4.7k.