Explain why a digital ammeter is more suitable than an analogue ammeter when measuring a very small current of a few milliamps in a circuit.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A digital ammeter can measure currents in the milliamps or microamps range, so a few milliamps will give a readable value.
An analogue ammeter normally has a range of 0.1–5 A; a few milliamps would be far below the lowest scale mark and would be difficult to read accurately.
The digital display shows the value as a precise number, eliminating the need for visual estimation.
Using an ammeter whose range places the current in the middle of its scale prevents overload and gives the most reliable measurement – the digital ammeter’s small range achieves this for milliamp currents.
An analogue ammeter normally has a range of 0.1–5 A; a few milliamps would be far below the lowest scale mark and would be difficult to read accurately.
The digital display shows the value as a precise number, eliminating the need for visual estimation.
Using an ammeter whose range places the current in the middle of its scale prevents overload and gives the most reliable measurement – the digital ammeter’s small range achieves this for milliamp currents.
Examiner tips
- Use the command word ‘Explain’ – give reasons, not just facts.
- Mention the range difference and the precision of the display.
- Show why a small‑range meter is safer and more accurate for tiny currents.
Common mistakes
- Saying the analogue meter is ‘more accurate’ – it is actually less suitable for milliamps.
- Forgetting to mention the risk of over‑loading the meter by using a too‑large range.
Mark scheme (4 marks)
- A digital ammeter can measure currents over a much smaller range (milliamps or microamps)
- An analogue ammeter typically measures over a larger range (e.g. 0.1–5 A), so a few milliamps would give a reading too small to read accurately on the scale
- A digital ammeter displays the measurement directly on a display, giving a precise numerical reading
- Using an ammeter whose range gives a reading in the middle of its range avoids damage and gives the most reliable measurement, and the digital ammeter's small range achieves this for milliamp currents
Key terms in this question
digital ammeter · analogue ammeter
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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