Which value is used to equate AC voltage to DC voltage for equivalent work?

The RMS value, or Root Mean Square value, is the correct choice because it provides a way to quantify the effective value of an alternating current (AC) or voltage in terms of direct current (DC) equivalent. This is particularly important in electrical engineering and practical applications, as AC voltages fluctuate with time in a sinusoidal manner.

The RMS value is calculated as the square root of the average of the squares of instantaneous values over one complete cycle. This allows it to effectively convey how much power an AC voltage would deliver compared to a corresponding DC voltage. For example, an RMS voltage of 120V AC would deliver the same amount of work as a steady 120V DC voltage.

Understanding the RMS value is crucial because simply taking the average or peak values of AC voltage does not accurately reflect its real-world effectiveness and power delivery in a circuit. Hence, the RMS value is a foundational concept in electrical engineering for comparing and working with AC and DC voltages.