Definition
The value of an alternating current (AC) voltage that produces the same heating effect in a resistance as a direct current (DC) voltage of the same numerical value. Effective voltage equals 0.707 times the peak voltage of a sine wave, and is also called the root-mean-square (RMS) voltage.
Plain English
AC voltage is constantly changing, so we need a single number to describe how much work it can really do. Effective voltage is that number — it tells you how much steady DC voltage would do the same job, like producing the same amount of heat in a wire.
Context Anchor
Seen in aircraft electrical-system study when comparing AC generator output, inverter output, and meter readings.
Derivation
‘Effective’ comes from the Latin effectivus, meaning ‘producing a result.’ The name fits: it’s the voltage figure that describes the actual working effect of AC, not its peak or its average.
Why Pilots Care
Correct effective-voltage values prevent miscalculating loads on aircraft electrical systems and ensure reliable operation of avionics and charging equipment.
Analogy
Think of effective voltage as the steady DC value that would do the same job as the rising and falling AC value. The AC voltage keeps changing, but its effective value gives you a practical single number to compare.
Intuition Check
Effective does not mean “the voltage left after losses” or “the best voltage.” Here it means the AC voltage value that has the same practical effect as a DC voltage.
Example Sentence 1
The aircraft’s AC bus operates at an effective voltage of 115 volts, even though the peak voltage of the waveform is closer to 163 volts.
Example Sentence 2
Avionics troubleshooting requires measuring effective voltage rather than peak voltage to avoid incorrect load estimates.