Introduction

This PSLE Science question tests your understanding of electric circuits—specifically how current and battery arrangement affect the brightness of a bulb.

The teacher compares four circuits that use identical bulbs and batteries to determine when Bulb L has the same brightness across different setups.

The Question

Mariam sets up four circuits using identical batteries and bulbs.
The goal is to find which circuits produce the same brightness for Bulb L.

The brightness depends on:

• number of batteries 
• whether they are arranged in series or parallel 
• how many bulbs share the current 

Step-by-Step Explanation (Matching Teacher’s Working)

Circuit A

• 1 battery 
• Bulb L has full current
  ➡️ Brightness = normal brightness 

Circuit B

• 1 battery 
• Same setup as A, identical load
  ➡️ Brightness is the same as Circuit A 

Circuit C

• 2 batteries in parallel 
• Parallel batteries do not increase voltage
  ➡️ Total voltage = same as ONE battery
  ➡️ Bulb L brightness stays the same as A & B 

However, in this PSLE Science question’s diagram, Circuit C’s layout splits current between bulbs — not identical to A & B.

So Circuit C does not produce the same brightness.

Circuit D

• 2 batteries, but in a configuration where Bulb L receives the same effective voltage and same load
  ➡️ Bulb brightness matches A and B 

Final Answer

Bulbs A, B and D have the same brightness.

Correct option:
✅ (4) A, B and D only

Key Concepts

Tips for Students

✔ Always check if batteries are in series or parallel
✔ Remember: Parallel batteries = same voltage
✔ Check how many bulbs share the same current
✔ A bulb’s brightness indicates the energy it receives per second

For Parents

Understanding circuits helps students with:

• Electricity topics 
• Energy transfer 
• Interpretation of diagrams 
• Logic-based PSLE questions 

Students often struggle with identifying battery arrangements—practising questions like this builds strong fundamentals.