Current division in parallel circuits — does total current split directly proportional to resistance values?

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction / Context:
Understanding how current divides among parallel branches is essential for sizing components and predicting power dissipation. This item targets the proportionality rule for current division.


Given Data / Assumptions:

  • Two or more resistors connected in parallel across a common voltage source.
  • Ohmic behavior (linear resistors) and steady-state conditions.


Concept / Approach:
In parallel, branch voltages are equal. Using Ohm’s law, branch current Ik = V / Rk. Therefore, current in a branch is inversely proportional to its resistance. Lower resistance draws more current, higher resistance draws less. The current divider formula for two branches is I1 = Itot * (R2 / (R1 + R2)), I2 = Itot * (R1 / (R1 + R2)). Note that each branch current multiplies by the opposite branch resistance in the numerator, embodying inverse proportionality.


Step-by-Step Solution:

Given V across all branches: I1 = V / R1, I2 = V / R2.Take ratios: I1 / I2 = (V / R1) / (V / R2) = R2 / R1.Thus, Ik ∝ 1 / Rk, not Rk.Apply current divider to compute each branch from total current if desired.


Verification / Alternative check:
Example: V = 10 V, R1 = 5 Ω, R2 = 10 Ω → I1 = 2 A, I2 = 1 A. The branch with half the resistance draws twice the current, consistent with inverse proportionality.


Why Other Options Are Wrong:

  • “True” would claim larger resistors get more current, which contradicts Ohm’s law under equal voltage.


Common Pitfalls:
Memorizing formulas without noting symmetry: the “opposite resistance” in the numerator is a cue that current is inversely related to resistance.


Final Answer:
False

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