How It Works: Why AC Peaks at 325 V But We Say 230 V

⚙️ How It Works: Why AC Peaks at 325 V But We Say 230 V

AC mains voltage constantly alternates between positive and negative values. In the UK, it peaks at approximately +325 V and -325 V. So why do we say the mains is 230 V?

230 V is the RMS (root mean square) voltage — a mathematical average that takes into account the constantly changing direction and magnitude of AC. RMS voltage is the equivalent DC voltage that would deliver the same power to a resistive load.

The formula relating peak to RMS is: V_rms = V_peak / √2. Since √2 ≈ 1.41: V_rms = 325 / 1.41 ≈ 230 V.

This is important for safety: the live wire is always at a potentially lethal voltage, even when an appliance is switched off, because it's still connected to the supply at the socket.