When using a voltmeter, how should the meter be connected to test voltage?

To accurately measure voltage with a voltmeter, it is essential to connect the meter in parallel with the load. This configuration allows the voltmeter to measure the potential difference across the load without significantly affecting the circuit's operation. When connected in parallel, the voltmeter can capture the voltage at the specific points of interest without altering the current flowing through the load.

If a voltmeter were connected in series with the load, it would create a break in the circuit and prevent current from flowing, which would not yield a meaningful voltage reading. Similarly, while measuring voltage at the power source might provide useful data for some applications, it doesn't give a complete understanding of how voltage behaves across individual components in the circuit. Grounding the voltmeter does not pertain to typical voltage measurement practices, as it does not provide any readings about the potential difference across components. Thus, connecting in parallel is the correct and standard approach for voltage measurement using a voltmeter.