Electricity lesson
Series Circuits: Current, PD & Resistance: Explore current, potential difference, and resistance in series circuits. Learn how components share voltage and…
Series Circuits: Current, PD & Resistance is part of Series and parallel circuits in GCSE AQA Higher Physics.
3 min
Reading time
24
Lessons in this topic
GCSE AQA Higher
Pathway
Expert reviewed
Content review
Series Circuits: Current, PD & Resistance: Explore current, potential difference, and resistance in series circuits. Learn how components share voltage and…
Use this lesson to stay inside Series and parallel circuits while connecting the detail back to the wider Electricity topic.
Read the core explanations from Series Circuits: Current, PD & Resistance before testing yourself from memory.
Picture Christmas lights that all go out when one bulb breaks. That's a series circuit - one continuous loop where everything depends on everything else. Understanding how current, voltage, and resistance behave in series circuits is crucial for GCSE Physics because these principles appear in every electricity exam question.
Series circuits follow three fundamental rules that seem simple but catch many students out. Get these right, and you'll unlock marks in calculations, explanations, and practical work.
If you have a 12V battery and two resistors, the voltages across each resistor will add up to 12V. The bigger the resistance, the bigger its share of the voltage.
Adding more resistors in series always increases the total resistance because every resistor adds extra opposition to the current. In parallel circuits the opposite happens: adding another branch gives charge more than one path to follow, so the total resistance decreases and is always less than the smallest branch resistance. This qualitative contrast is a standard GCSE explanation and helps you decide which rule to apply before you start calculating.
These two equations are your toolkit for every series circuit calculation. The key insight is that current stays the same, so you can use Ohm's law on individual components or the whole circuit.
This practical proves the theory works in real life. Set up a series circuit with a power supply, resistor, ammeter and voltmeter. Change the resistor combination, record current and potential difference, then compare the measured values with your calculated totals. Keep the supply voltage controlled, read meters at eye level, and switch off the circuit between changes to reduce heating errors. The aim is to show that current stays the same in series and that the voltage drops add to the supply voltage.
| Property | Series Circuit | Parallel Circuit |
|---|---|---|
| Current | Same through all components | Splits between branches |
| Voltage | Shared between components | Same across all components |
| Total Resistance | Sum of all resistances | Less than smallest resistance |
| Effect of adding resistors | Increases total resistance | Decreases total resistance |
| If one component breaks | Whole circuit stops | Other components keep working |
The key difference is the path for current. Series has one path (like a single-lane road), while parallel has multiple paths (like a motorway with several lanes).
Series circuit questions follow predictable patterns. First identify whether the circuit is truly series or whether there are parallel branches hidden in the diagram. Then write the rule you need: current is the same, voltages add to the supply, and resistances add directly. Once you have stated the correct rule, substitute values with units and show each step so method marks are protected even if the arithmetic slips.
Common exam traps include mixing up series and parallel rules, forgetting to convert units (mA to A), and not showing working clearly. Always state your formula, substitute values with units, and give your final answer with correct units.
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Explore current, potential difference, and resistance in series circuits. Learn how components share voltage and affect total resistance.
By the end of this lesson, you should be able to Explain why current is the same throughout a series circuit; Calculate total resistance when resistors are connected in series; Describe how potential difference is shared between components in series; Apply Ohm's law to series circuit calculations.
Read each section, then close the notes and explain the idea from memory. Check your explanation against the page and finish with an exam question from Electricity.