Parallel networks — if you add more resistors in parallel, do total resistance and total current behave as stated? Claim: Adding resistors in parallel increases total resistance and decreases total current.

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction / Context:
This statement probes the hallmark property of parallel circuits: how total or equivalent resistance changes as additional branches are added, and how that affects the current drawn from a fixed-voltage source.


Given Data / Assumptions:

  • Resistors connected in parallel between the same two nodes of an ideal voltage source.
  • Ohm’s law applies; source voltage remains constant.
  • No wire resistance or parasitic effects.


Concept / Approach:
The equivalent resistance of resistors in parallel is found from conductances: 1/Req = 1/R1 + 1/R2 + … . Adding another parallel branch adds positive conductance, so Req must decrease. With a fixed source voltage, the total current Itot = V / Req therefore increases when Req decreases. Thus the claim in the stem is the opposite of the true behavior.


Step-by-Step Solution:

Start with two resistors: 1/Req = 1/R1 + 1/R2 → Req = (R1 * R2) / (R1 + R2) < min(R1, R2).Add a third resistor R3: new 1/Req' = 1/Req + 1/R3 → Req' < Req.For fixed V: Itot = V / Req increases as Req decreases.Therefore, adding resistors in parallel decreases total resistance and increases total current drawn.


Verification / Alternative check:
Numerical example: V = 12 V; R1 = 12 Ω gives Itot = 1 A. Add R2 = 12 Ω in parallel: Req = 6 Ω, Itot = 2 A. Add R3 = 12 Ω: Req = 4 Ω, Itot = 3 A. The pattern confirms the rule.


Why Other Options Are Wrong:

  • Choosing “True” confuses parallel with series behavior. Series connections increase resistance as more resistors are added; parallel decreases it.


Common Pitfalls:
Using arithmetic averages or adding magnitudes directly; always combine parallel resistances via reciprocals or conductances.


Final Answer:
False

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