Series combination of capacitive reactances — qualitative effect on total Xc When capacitive reactances are connected in series, what happens to the total capacitive reactance of the combination?
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Aan increase in total XC
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Ba decrease in total XC
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Cno change in total XC
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Dtotal opposition to voltage in the circuit
Answer
Correct Answer: an increase in total XC
Explanation
Introduction / Context:Knowing how reactances combine helps anticipate impedance and voltage distribution in AC networks. For series networks, impedances simply add as complex quantities.
Given Data / Assumptions:
- Two or more capacitive reactances Xc1, Xc2, ... connected in series.
- Sinusoidal steady-state analysis.
- Ideal linear elements.
Concept / Approach:Impedances in series add: Z_total = Σ Zi. For purely capacitive branches, Zi = -jXci. Thus Xc,total = Xc1 + Xc2 + ... . Adding positive magnitudes yields a larger total reactance magnitude, meaning greater opposition to AC current.
Step-by-Step Solution:Write each branch impedance: Zi = -jXci.Series sum: Z_total = -j(Xc1 + Xc2 + ...).Magnitude increases with each additional series reactance: |Z_total| = Xc1 + Xc2 + ... .Therefore, the total capacitive reactance increases when connected in series.
Verification / Alternative check:Duality with resistors: resistances in series also add. In contrast, capacitors themselves (as components) in series reduce equivalent capacitance, but their individual reactances at a given frequency still add.
Why Other Options Are Wrong:
- Decrease or no change: contradicts series impedance addition.
- “Total opposition to voltage”: imprecise; reactance describes opposition to AC current at a given frequency.
Common Pitfalls:
- Mixing up capacitor combination rules (for C values) with reactance combination (for Xc values).
- Forgetting frequency dependence; Xc changes with f even if component values are fixed.
Final Answer:an increase in total XC