Ideal voltage source model: Does an ideal voltage source have zero internal resistance so that its terminal voltage remains fixed regardless of load current?
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ATrue
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BFalse
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CTrue only for AC sources
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DTrue only when the load is purely resistive
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EFalse unless two sources are connected in series
Answer
Correct Answer: True
Explanation
Introduction / Context:An ideal voltage source is a theoretical construct used in circuit analysis to simplify behavior: it maintains a specified terminal voltage independent of the current demanded by the load.
Given Data / Assumptions:
- Two-terminal ideal source with fixed voltage Vs.
- No internal energy or thermal limits considered (theoretical model).
- Load may vary arbitrarily.
Concept / Approach:
The ideal voltage source is modeled with zero internal resistance (Rint = 0). With Rint = 0, the terminal voltage equals Vs for any load current. Any nonzero Rint results in a voltage drop V_drop = I_load * Rint, making the terminal voltage depend on load current and invalidating ideal behavior.
Step-by-Step Solution:
Represent the source as Vs in series with Rint.For ideal behavior, set Rint = 0 → V_terminal = Vs independent of I_load.If Rint > 0, then V_terminal = Vs − I_load * Rint varies with load, demonstrating non-ideal regulation.Therefore, the ideal voltage source requires zero internal resistance.Verification / Alternative check:
Duality: the ideal current source has infinite internal resistance. Thevenin equivalents use low Rth to approximate voltage sources; lower Rth approaches the ideal limit.
Why Other Options Are Wrong:
- The ideal definition holds for DC and AC; frequency is irrelevant.
- Load type does not affect ideal source behavior; it remains fixed-voltage by definition.
- Series-connecting sources does not change the internal resistance idealization.
Common Pitfalls:
Confusing practical low-impedance sources (small but nonzero internal resistance) with the idealized zero-resistance model; always distinguish theory from real devices.
Final Answer:
True