What is the function of a voltmeter in electrical systems?

The function of a voltmeter in electrical systems is to measure the electric potential difference, or voltage, between two points in a circuit. This measurement is crucial for understanding how much electrical energy is available to do work in the system. A voltmeter provides critical information about the voltage level, which helps in diagnosing issues within an electrical circuit, ensuring that components are operating within their specified voltage range.

Measuring the rate of charge in a battery relates to current and is typically performed by an ammeter, making that option not suitable for the voltmeter's function. Indicating total energy consumption would require measuring both voltage and current, which is typically the role of a wattmeter, not a voltmeter. Detecting the presence of electrical currents is more appropriately attributed to devices like ammeters or current sensors, while calculating resistance requires measuring voltage and current simultaneously, thus using Ohm's Law rather than a voltmeter alone.