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High school physics
Course: High school physics > Unit 12
Lesson 4: DC Ammeters and voltmetersDC Ammeters and voltmeters review
Review the key terms and skills related to voltmeters and ammeters, including where to place them in a circuit.
Key terms
| Term | Meaning | |
|---|---|---|
| Ammeter | Instrument used to measure current. | |
| Voltmeter | Instrument used to measure electric potential difference. |
How are ammeters and voltmeters represented in a circuit?
Ammeters are typically represented by a circle with a letter A inside (Figure 1).
Voltmeters are typically represented by a circle with a letter V inside (Figure 2).
How to use ammeters and voltmeters
Ammeters measure the current through components. To measure the current going through a component, the ammeter is connected in series with the components we want to investigate. Resistors in series experience the same current (Figure 3). Typically, ammeters have negligible resistance, so they do not affect the circuit.
For example, if we want to find the current through R, start subscript, 1, end subscript in the circuit below, the ammeter is placed in series with R, start subscript, 1, end subscript.
Voltmeters measure the electric potential drop across components. The voltmeter is placed in parallel with the component of interest because components in parallel experience the same potential difference.
For example, if we want to measure the electric potential drop across resistor R, start subscript, 2, end subscript, the voltmeter should be arranged in parallel with the resistor (R, start subscript, 2, end subscript).
Learn more
For deeper explanations, see our video on ammeters and voltmeters.
To check your understanding and work toward mastering these concepts, check out the exercise on ammeters and voltmeters.
Want to join the conversation?
is there any instrument made to measure resistance(4 votes)
Yes, a multimeter can measure voltage, current, and resistance.(6 votes)
- Ideally the internal resistance of a voltmeter should be infinite and that of an ammeter should be zero. Why is it so?(2 votes)
- Hello,
In a voltmeter you are measuring in paralell. You do not want to be involved in the circuit essentially, only measure it. So you want nothing to go through the voltmeter and electricity takes the path of least resistance, so it will not go through the voltmeter if it has lots and lots of resistance. In an ammeter, you are measuring current, the electricity is going through the meter. You do not want your measurement to affect the current, and you do that by having lots of resistance. Hope this helps.
AP Physics Student(2 votes)