What is the effective value that voltmeters typically indicate?

Voltmeters are designed to measure the effective value of alternating current (AC) voltage, which is most commonly represented as Root Mean Square (RMS) voltage. The RMS value of a voltage provides a meaningful measure for assessing the energy delivery capability of an AC voltage, as it represents the equivalent direct current (DC) voltage that would deliver the same amount of power to a load.

When you consider an AC waveform, such as a sine wave, its variances over time can make it difficult to gauge its performance or effects based solely on peak or average values. The RMS value accounts for this by mathematically translating the varying voltage levels into a single, constant value that reflects its overall power capacity.

In contrast, peak voltage merely shows the maximum level reached by the waveform, and instantaneous voltage indicates the voltage at a specific moment in time. Average voltage can be misleading when working with AC signals, as it does not accurately reflect the power capacity due to the wave's cyclical nature. Thus, for applications that involve assessing and comparing electrical energy, the RMS value becomes the standard reference, making it the value that voltmeters typically indicate.