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→Key Stage 4
: An ideal [[voltmeter]] has infinite [[Electrical Resistance|resistance]] because otherwise adding an [[voltmeter]] to a [[circuit]] would change the [[Potential Difference|potential difference]] between the two points.
: [[Voltmeter]]s can be [[Analogue Voltmeter|analogue]] with a needle pointing to numbers on a dial or it can be [[Digital Voltmeter|digital]] with a number display.
{| class="wikitable"
|+Using a voltmeter on components in series.
|-
|[[File:CircuitDiagramBatteryBulbBulbSeries.png|center|200px]]
|[[File:CircuitDiagramBatteryBulbBulbSeries.png|center|200px]]
|-
| style="height:20px; width:200px; text-align:center;" |To [[measure]] the [[Potential Difference|potential difference]] across bulb 1 the [[voltmeter]] must be placed in [[Parallel Circuit|parallel]] with bulb 1.
| style="height:20px; width:200px; text-align:center;" |To [[measure]] the [[Potential Difference|potential difference]] across bulb 2 the [[voltmeter]] must be placed in [[Parallel Circuit|parallel]] with bulb 2.
|-
|[[File:CircuitDiagramBatteryBulbVoltmeterBulbSeries.png|center|200px]]
|[[File:CircuitDiagramBatteryBulbBulbVoltmeterSeries.png|center|200px]]
|}
{| class="wikitable"
|+Using a voltmeter on components in parallel.
|-
|[[File:CircuitDiagramBatteryBulbBulbParallel2.png|center|200px]]
|[[File:CircuitDiagramBatteryBulbBulbParallel2.png|center|200px]]
|-
| style="height:20px; width:200px; text-align:center;" |To [[measure]] the [[Potential Difference|potential difference]] across bulb 1 the [[voltmeter]] must be placed in [[Parallel Circuit|parallel]] with bulb 1.
| style="height:20px; width:200px; text-align:center;" |To [[measure]] the [[Potential Difference|potential difference]] across bulb 2 the [[voltmeter]] must be placed in [[Parallel Circuit|parallel]] with bulb 2.
|-
|[[File:CircuitDiagramBatteryBulbVoltmeterBulbParallel.png|center|200px]]
|[[File:CircuitDiagramBatteryBulbBulbVoltmeterParallel.png|center|200px]]
|-
| style="height:20px; width:200px; text-align:center;" colspan = "2"|In this case both [[voltmeter]]s will give the same [[measure]]ment because the [[Electrical Component|components]] themselves are in [[Parallel Circuit|parallel]].
|}