Series–parallel in practice: A “loaded voltage divider” (a resistor divider that feeds a finite load) is a common and important application of series–parallel circuits. Determine whether this usage description is accurate.
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ACorrect
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BIncorrect
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CTrue only if the load is very large
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DValid only in low-voltage electronics
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EApplies to AC circuits only
Answer
Correct Answer: Correct
Explanation
Introduction / Context:Many real circuits use resistor dividers to derive reference or bias voltages. The moment a load is attached to a divider output, the circuit becomes a series–parallel network: the lower divider resistor is effectively in parallel with the load. Recognizing this is essential for predicting output sag and source current changes.
Given Data / Assumptions:
- Two-resistor divider from a DC supply.
- Finite load R_L from the divider output to ground.
- Resistive behavior; frequency effects ignored.
Concept / Approach:With a load present, the bottom leg and R_L form a parallel combination. The output voltage becomes V_out = V_in * (R_bottom || R_L) / (R_top + (R_bottom || R_L)). This is a textbook series–parallel transformation and a standard example used to introduce loading effects in basic circuit courses.
Step-by-Step Solution:
Identify the divider: R_top and R_bottom in series across V_in.Attach R_L across the output node to ground.Compute R_lower_eff = R_bottom || R_L.Use the series formula to compute V_out and confirm series–parallel nature.Verification / Alternative check:Measure V_out with and without the load; the loaded case is lower, matching the series–parallel formula prediction.
Why Other Options Are Wrong:
- Incorrect / only large load / low-voltage only / AC only: The classification as series–parallel does not depend on voltage level or frequency for resistive circuits and holds for any finite load.
Common Pitfalls:Designing a divider without considering R_L, leading to excessive voltage sag or wasted current; forgetting to buffer the divider with an op-amp follower when a stiff source is required.
Final Answer:Correct