What does “16 V AC” mean?
A light bulb should give the same brightness with 16 V AC as it does with 16 V DC. That’s by definition. “16 V AC” means “AC as efficient as 16 V DC”.
Instead of “16 V AC” we could write “16 Veff AC” to indicate that it is the effective voltage. Without further specification voltages normally refer to the effective voltage.
With “16 V DC” we will have 16 V all of the time. With AC the output voltage will be 0 V 100 times a second (at 50 Hz) or 120 times a second (at 60 Hz) respectively.
So to get the same brightness from 16 V AC, the peak voltage will have to be higher than 16 V. And it is. With sine wave AC the peak voltage is the effective voltage multiplied by square root of 2. That’s about 41 % more.
So with 16 V AC and a sine wave, the voltage will rise from 0 V to a peak of 22.6 V, will go down to 0 V again, will sink further to -22.6 V and back to 0 V – and the next cycle begins.
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