Building Series and Parallel Circuits

Purpose

Measure current and potential difference in series and parallel circuits, and state the rules for each from your own measurements.

Safety

Have every circuit checked before switching on. Never connect an ammeter directly across the battery.

Procedure

Part A — series

1. Build: battery, switch, two identical lamps in one loop.
2. Measure current at three points: before lamp 1, between the lamps, after lamp 2.
3. Measure potential difference across each lamp, then across both together.

Part B — parallel

1. Rebuild with the two lamps on separate branches.
2. Measure current in each branch and in the main line.
3. Measure potential difference across each lamp.

Data

Series

Measurement	Value
Current before lamp 1
Current between lamps
Current after lamp 2
$V$ across lamp 1
$V$ across lamp 2
$V$ across both

Parallel

Measurement	Value
Current in branch 1
Current in branch 2
Current in main line
$V$ across lamp 1
$V$ across lamp 2

Analysis

1. Write a rule for current in series, and one for parallel, using your numbers.
2. Do the same for potential difference.
3. Which arrangement made the lamps brighter? Explain using total resistance.
4. Unscrew one lamp in each circuit. What happens, and why does that explain how houses are wired? See Series and Parallel Circuits.

Hand in

• Both data tables
• Four rules, stated in your own words with supporting numbers
• Analysis answers

Curriculum connection

D2.6

construct series and parallel circuits to compare electric current, potential difference, and resistance in both types of circuits

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A1.2

apply a scientific experimentation process and associated skills to conduct investigations, making connections between their observations and findings and the scientific concepts they are learning

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