How is a voltmeter connected to a component to measure applied voltage?

To measure the voltage (electric potential difference) across a component, a voltmeter must be connected in parallel with that component. This allows the meter's probes to touch both sides of the component simultaneously to measure the difference in pressure without interrupting the rest of the circuit. Voltmeters are specifically designed with a very high internal resistance so that they draw almost no current when connected across a circuit. If you were to incorrectly connect a voltmeter in series, its high resistance would severely restrict the current, stopping the circuit from functioning normally.