Series resistors share a single current path, so their voltage drops add.
Difficulty
Beginner
Read time
5 min
Prerequisites
Basic algebra and consistent SI units
Source
OpenStax, College Physics 2e, §21.1 (Paul Peter Urone and Roger Hinrichs)Textbook reference retained from the OpenFormulaGraph dataset; adaptation credits and license are provided below.
Adapted from OpenFormulaGraph, under CC BY 4.0.
FormuLab adapted the notation, explanations, assumptions, and topic placement, and expanded the numerical check into a worked example.
Series resistors share a single current path, so their voltage drops add. Their equivalent resistance is the sum of their individual resistances. The same rule extends to more than two resistors.
| Symbol | Meaning | Units |
|---|---|---|
| Equivalent series resistance | ||
| First resistance | ||
| Second resistance |
Replace a series pair by one equivalent resistor.
Find the total resistance of a divider chain.
Ideal resistors of 3.00 Ω and 5.00 Ω are connected in series. Find their equivalent resistance.
Textbook reference retained from the OpenFormulaGraph dataset; adaptation credits and license are provided below.
Adapted from OpenFormulaGraph, under CC BY 4.0.
FormuLab adapted the notation, explanations, assumptions, and topic placement, and expanded the numerical check into a worked example.
Assumptions
FormuLab is a study reference. Verify formulas, units, assumptions, and course-specific conventions before relying on them.
© 2026 FormuLab. All rights reserved.