PhysicsChapter 7: Current Electricity
Meters in A Circuit
Introduction
Two important electrical measuring instruments are the ammeter and the voltmeter.
Definition
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.
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Meters in A Circuit
Sticky Notes · Quick Revision
A
- Series
V
- Parallel
AMMETER
- Low resistance
VOLTMETER
- High resistance
60-second revision
- Ammeter → current → series → low R.
- Voltmeter → p.d. → parallel → high R.
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