PhysicsChapter 11: Electricity

Resistors in Series

Resistors connected end to end with no junction form a series combination. The circuit has one path, so the same current passes through every resistor.

Rules to remember

Key equation

I=I₁=I₂=I₃=⋯

Key equation

V=V₁+V₂+V₃+⋯

Key equation

R_eq=R₁+R₂+R₃+⋯

Current is the same through all resistors.
Individual voltage drops add to the source voltage.
Equivalent resistance is greater than every individual resistance.
For N identical resistors, Req=NR.

Voltage division

Key equation

V₁V₂=R₁R₂

Because the current is common, the larger resistance has the larger voltage drop.

Quick solved example

For 2 Ω, 3 Ω and 5 Ω in series across 20 V:

Key equation

R_eq=2+3+5=10\ Ω

Key equation

I=2010=2\ A

Key equation

V₁=4\ V, V₂=6\ V, V₃=10\ V

Did you understand this topic?

Your answer is saved with your learning record. It does not mark the topic as mastered.

Exam preparation

Exam Focus

Quick revision

Revision Zone

Review the key facts, formulas and checks before you move on.