IGCSE 0625 / Section 4.3.2 / Core

One loop, one current.

String the components in a single loop and the current has only one road to travel, so it is the same everywhere. The push from the supply, though, gets shared out along the way.

The key idea

In a series circuit there is a single path, so the current is the same at every point. The supply voltage is shared as potential difference across the components, and the total resistance is the sum of the individual resistances.

Definition · learn the exact words

In a series circuit the components form a single loop. The current is the same at every point, the supply voltage is shared between the components, and the resistances add.

R total = R₁ + R₂ + ...

More resistors in series means a larger total resistance and a smaller current.

Section 01

Follow the single loop.

Add resistors in series and watch the current stay equal everywhere while the voltage shares out.

Stage 1 · Learn

Check series

Four quick checks. Each correct answer earns XP and lights this skill on your star map.

Quick check+10 XP

In a series circuit the current is...

Quick check+10 XP

In a series circuit the supply voltage is...

Quick check+10 XP

The total resistance of resistors in series is...

Quick check+10 XP

Adding more resistors in series makes the total resistance...

Section 02

Same current, shared voltage.

The one rule that current is equal everywhere, and the two that voltage shares and resistances add.

Worked example

A 3.0 Ω resistor and a 5.0 Ω resistor are connected in series. Find the total resistance.

Step 1 · Add the resistancesR = R₁ + R₂
Step 2 · SubstituteR = 3.0 + 5.0
Step 3 · AnswerR = 8.0 Ω
Examiner trap

In series the current is the same all the way round, it is not shared. It is the voltage that is shared between the components, and the resistances add up.

Stage 2 · Exam

Exam-style questions

Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.

Finish the four checks above to unlock the exam questions
Exam style+20 XP

A 3.0 Ω and a 5.0 Ω resistor are in series. The total resistance is...

Exam style+20 XP

Two identical lamps are connected in series across a 6.0 V supply. The voltage across each lamp is...

Exam style+20 XP

The current leaving the battery in a series circuit is 0.40 A. The current through a resistor further round the loop is...

Skill unlocked

Series, mastered.

Series circuits are mapped. Keep the chain going.

-Rank -Level -Score -Topics
Go deeper · practice
Six original Cambridge-style questions
Current, voltage and resistance rules in a series circuit and adding resistances. Attempt each, then reveal the worked solution.
Stage 3 · master the unit
Electricity and magnetism challenge
Mixed questions across the whole unit, each one worth XP. Start this only when you feel confident across every topic in the unit, not just series.
Start the unit challenge →