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## High school physics

### Course: High school physics>Unit 12

Lesson 4: DC Ammeters and voltmeters

# DC 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

TermMeaning
AmmeterInstrument used to measure current.
VoltmeterInstrument 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).
Figure 1. Symbol for ammeter.
Voltmeters are typically represented by a circle with a letter V inside (Figure 2).
Figure 2. Symbol for voltmeter.

## 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.
Figure 3: Ammeter A, start subscript, 1, end subscript in series with R, start subscript, 1, end subscript so it measures the current through R, start subscript, 1, end subscript. Ammeter A, start subscript, 2, end subscript in series with R, start subscript, 2, end subscript so it measures the current through R, start subscript, 2, end subscript. Ammeter A, start subscript, 3, end subscript in series with the battery so it measures the current through it.
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).
Figure 2: Voltmeter V in parallel measures potential drop across resistor R, start subscript, 2, end subscript in the circuit.