Facebook
Google
GitHub
LinkedinNetwork Analysis Techniques
AC Network Analysis
24 questions By Tony R. Kuphaldt
-
Question 7 of 24
Explain why this bridge circuit can never achieve balance:
Reveal answerEven though impedance magnitudes may be balanced, the phase angles cannot.
Follow-up question: explain why it would not work to use an oscilloscope as the “detector” in this bridge circuit:
Hint: beware of ground connections!
Challenge question: explain how you could use this same oscilloscope as the detector in this bridge circuit without changing the ground location at the lower terminal of the AC source.
Notes:Explain to your students that AC bridges, while fundamentally the same as DC bridges, do have their differences. Their knowledge of AC circuit calculations (with complex numbers) should be enough for them to see why this is so.
-
Question 8 of 24
Calculate the impedance value necessary to balance this AC bridge, expressing your answer in both polar and rectangular forms:
Reveal answerZ = 1.975 kΩ ∠ 90o (polar form)
Z = 0 j1.975 kΩ (rectangular form)
Follow-up question: what type and size of component will provide this exact amount of impedance at 400 Hz?
Notes:So long as complex quantities are used, AC bridge circuits “balance” just the same way that DC bridge circuits balance. Consequently, this is really nothing new for your students if they’ve already studied DC Wheatstone bridge circuits.
-
Question 9 of 24
Calculate the impedance value necessary to balance this AC bridge, expressing your answer in both polar and rectangular forms:
Also, describe what sort of device might be appropriate to serve as a “null detector” to indicate when bridge balance has been achieved, and where this device would be connected to in the bridge circuit.
Reveal answerZ = 337.6 Ω ∠ -90o (polar form)
Z = 0 - j337.6 Ω (rectangular form)
The simplest “null detector” for this type of AC bridge would be a sensitive pair of audio headphones, as 600 Hz is well within the audio range, and would be heard as a tone in the headphones.
Follow-up question: what type and size of component will provide this exact amount of impedance at 600 Hz?
Notes:So long as complex quantities are used, AC bridge circuits “balance” just the same way that DC bridge circuits balance. Consequently, this is really nothing new for your students if they’ve already studied DC Wheatstone bridge circuits.
