Voltmeter

Key Stage 3

A picture showing an analogue voltmeter.

A voltmeter is a measuring device used to measure the potential difference between two points in a circuit.

Voltmeters are added in parallel to components in a circuit to find the potential difference between two points.

An ideal voltmeter has infinite resistance because otherwise adding an voltmeter to a circuit would change the Potential Difference between two points.

Voltmeters can be analogue with a needle pointing to numbers on a dial or it can be digital with a number display.


A voltmeter placed in parallel with a bulb.

A voltmeter is a measuring device used to measure the potential difference between two points in a circuit.

Voltmeters are added in parallel to components in a circuit to find the potential difference between two points.

An ideal voltmeter has infinite resistance because otherwise adding an voltmeter to a circuit would change the potential difference between the two points.

Voltmeters can be analogue with a needle pointing to numbers on a dial or it can be digital with a number display.

Using a voltmeter on components in series.

To measure the potential difference across bulb 1 the voltmeter must be placed in parallel with bulb 1.	To measure the potential difference across bulb 2 the voltmeter must be placed in parallel with bulb 2.

Using a voltmeter on components in parallel.

To measure the potential difference across bulb 1 the voltmeter must be placed in parallel with bulb 1.	To measure the potential difference across bulb 2 the voltmeter must be placed in parallel with bulb 2.

In this case both voltmeters will give the same measurement because the components themselves are in parallel.