The effective value of a sine wave of voltage or current is:

The 'effective' value of an alternating current or voltage is the value that produces the exact same heating effect in a resistor as a direct current (DC) of the same value. In electronics, this is synonymous with the Root Mean Square (RMS) value. Mathematically, the RMS or effective value of a pure sine wave is calculated by dividing its maximum (peak) value by the square root of 2. This calculation results in approximately 0.707. Therefore, the effective value is always 70.7% of the maximum peak value. Options like 63.6% represent the average value, which is not the same as the effective work-producing value.