Our mains is '230 V', but I read the peak is about 325 V — which is right?
Both.
Both. AC voltage swings up and down, so we quote its rms (effective) value, which delivers the same heating as a steady DC of that value. The rms and peak are related by Vrms = V0/√2. So a 230 V rms supply actually peaks at V0 = 230 × √2 ≈ 325 V. Meters and ratings use rms; the instantaneous voltage still reaches the higher peak.
Key point
Vrms = V0/√2, so 230 V rms ≈ 325 V peak.
Common mistake
reading the stated mains voltage as the peak value.
Memory tip
stated AC voltage is rms; multiply by √2 for the peak.
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