Series resistors — evaluating the claim: “Total series resistance equals the difference between largest and smallest resistor.” Is this statement true or false?

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction / Context:
This item checks fundamental circuit theory for series connections. In series, the same current flows through each element, and resistances combine in a straightforward way. Misconceptions here can cascade into errors in power dissipation and voltage-divider design.


Given Data / Assumptions:

  • N resistors R1, R2, …, RN connected in series.
  • Ideal components (no temperature coefficients or parasitics considered).


Concept / Approach:
The equivalent resistance of series elements is the sum of their resistances because voltage drops add while current is common: R_eq = R1 + R2 + … + RN. A “difference between largest and smallest” (R_max − R_min) ignores the contribution of intermediate elements and is physically unjustified except in trivial corner cases that still do not generalize.


Step-by-Step Solution:

State series rule: R_eq = sum over all individual resistances.Counterexample: with 2 Ω, 5 Ω, 8 Ω in series, R_eq = 2 + 5 + 8 = 15 Ω; R_max − R_min = 8 − 2 = 6 Ω, not equal to 15 Ω.Explain why: each resistor adds an incremental voltage drop at the same current, so contributions are additive, not canceling.


Verification / Alternative check:
Measure total resistance with an ohmmeter across the series string—the reading is the arithmetic sum. Kirchhoff’s Voltage Law likewise confirms additive drops around the loop.


Why Other Options Are Wrong:

  • Choosing “True” contradicts both KVL and the definition of resistance in series.


Common Pitfalls:
Confusing series and parallel formulas; mistakenly subtracting because voltage drops can oppose in some AC phasor contexts (which is not applicable to purely resistive DC series networks).


Final Answer:
False

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