lesson
Change the supply carefully
1 · Learn
In a suitable simple circuit, changing the number or voltage of correctly connected cells can change lamp brightness or buzzer loudness. Components have limits: adding more cells is not a safe way to make an unlimited brighter light.
A fair comparison uses the same rated lamp, wires and arrangement while the approved supply changes. Record what changed and what stayed the same. Cell condition can also affect the result.
2 · Worked example
An adult provides two approved supply settings within a lamp's rating. I compare brightness without changing the lamp at the same time, so the supply is the intended variable.
3 · Your turn
Why is changing both the lamp and the number of cells a poor test of only the cell number?
Check your answer
Two factors changed, so a difference cannot confidently be attributed to the cell number alone.
4 · Apply your learning
Plan a comparison on paper; use supplied observations if safe rated equipment is unavailable.
Adult guidance and safety
Adult controls the equipment and voltage. Do not stack cells beyond ratings, touch hot components or use mains power.
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Check a calculation · Year 5 onward
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