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Meters in a Circuit
An ammeter measures current in series; a voltmeter measures p.d. in parallel.
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Meters in a Circuit
Want to measure current? Put the meter in the path → ammeter in series.
Want to measure voltage? Put it across the component → voltmeter in parallel.
Recommended for Class 10
Meters in a Circuit
Two important electrical measuring instruments are the ammeter and the voltmeter.
Ammeter
An ammeter measures electric current.
It must be connected in series with the component whose current is being measured.
An ideal ammeter has very low resistance so that it does not significantly change the circuit current.
Voltmeter
A voltmeter measures potential difference between two points.
It is connected in parallel across a component.
An ideal voltmeter has very high resistance so that very little current passes through it.
Why Connections Matter
Connecting an ammeter directly across a source can produce a very large current because of its low resistance.
Connecting a voltmeter in series can greatly reduce current because of its high resistance.
Meters in a Circuit — Advanced
Measuring instruments should disturb a circuit as little as possible.
This is why an ammeter approaches zero internal resistance while a voltmeter approaches infinite resistance in the ideal model.
Common Mistakes
Common Mistakes
- Mistake
Ammeter → series.
- Mistake
Voltmeter → parallel.
- Mistake
Do not swap them.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Ammeter → current → series → low R.
Voltmeter → p.d. → parallel → high R.
- Definition
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Practice
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Q1. What does an ammeter measure?
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Q2. How is it connected?
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Q3. What does a voltmeter measure?
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Q4. How is it connected?
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Q5. Why should a voltmeter have high resistance?
Exam Practice
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Q1. Describe ammeter connection.
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Q2. Describe voltmeter connection.
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Q3. Compare their ideal resistances.
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Q4. Explain why ammeter should not be placed directly across a cell.
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Q5. Explain why voltmeter is connected across a component.
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.