---
title: "Alternating current (AC) — what it means"
description: "Alternating current. On a power supply it marks the mains input side. What the symbol looks like, what happens if you ignore it, and where its meaning differs by cou"
url: https://atoneplace.net/symbol/electrical-ac/
site: "At One Place"
---

# Alternating current (AC)

**Alternating current (AC): Alternating current. On a power supply it marks the mains input side.**

∿

## What it looks like

A single wave — one shallow S laid on its side.

## What it means

On the label of an adapter the wave sits beside the input figures — for instance 100–240 V and 50/60 Hz, which is what makes a charger usable worldwide with only a plug adaptor. A wave with a straight line above or below it means the equipment works on both AC and DC. Getting the two confused matters most with replacement power supplies, where feeding AC into a DC input destroys the device immediately.

> Defined by IEC 60417-5032. Where a symbol differs between standards, the difference is described above rather than resolved — both versions are in circulation on real labels.

## Other electrical and appliance symbols

| Symbol | Means |
| --- | --- |
| CE mark | The manufacturer declares the product meets the EU rules that apply to it. |
| UKCA mark | The manufacturer declares the product meets Great Britain's rules — the British counterpart to CE. |
| UL Listed | A complete product tested by Underwriters Laboratories against its safety standard. |
| UL Recognized Component | A component certified for use inside a larger product — not a certification of the finished item. |
| FCC mark | The device meets US limits on radio-frequency interference. |
| RoHS compliant | The product restricts ten hazardous substances, including lead, mercury, cadmium and four phthalates. |
| Crossed-out wheelie bin (WEEE) | Do not put this in household waste — take it to a separate collection for electrical items or batteries. |
| Crossed-out bin with Pb, Cd or Hg | A battery for separate collection which also contains lead, cadmium or mercury above the reporting threshold. |
| Double insulated (Class II) | The appliance is protected by two layers of insulation and needs no earth connection. |
| Protective earth (ground) | This terminal must be connected to the protective earth conductor. |
| IP rating (IP67, IPX4) | How well the enclosure keeps out solids and water. First digit solids 0–6, second digit water 0–9. |
| EU energy label (A to G) | How efficient the appliance is, on a scale from A to G, alongside consumption figures. |
| EnergyGuide label (US) | The estimated annual energy cost of this appliance in the US, and how it compares with the range for its class. |
| Direct current (DC) | Direct current. On a power supply it marks the output side. |
| Barrel jack polarity (centre positive or centre negative) | Which conductor of a barrel plug is positive: the inner pin or the outer sleeve. |

## Common questions

### What does the alternating current (ac) symbol mean?

Alternating current. On a power supply it marks the mains input side.

### What does it look like?

A single wave — one shallow S laid on its side.

## Related pages

- [Direct current (DC)](https://atoneplace.net/symbol/electrical-dc/)
- [Barrel jack polarity (centre positive or centre negative)](https://atoneplace.net/symbol/electrical-polarity/)
- [Protective earth (ground)](https://atoneplace.net/symbol/electrical-protective-earth/)
- [CE mark](https://atoneplace.net/symbol/electrical-ce/)
- [UKCA mark](https://atoneplace.net/symbol/electrical-ukca/)
- [UL Listed](https://atoneplace.net/symbol/electrical-ul-listed/)
- [UL Recognized Component](https://atoneplace.net/symbol/electrical-ul-recognized/)
- [FCC mark](https://atoneplace.net/symbol/electrical-fcc/)
- [RoHS compliant](https://atoneplace.net/symbol/electrical-rohs/)
- [Crossed-out wheelie bin (WEEE)](https://atoneplace.net/symbol/electrical-weee/)
- [Crossed-out bin with Pb, Cd or Hg](https://atoneplace.net/symbol/electrical-battery-bin/)
- [Double insulated (Class II)](https://atoneplace.net/symbol/electrical-double-insulated/)
- [Protective earth (ground)](https://atoneplace.net/symbol/electrical-protective-earth/)

## Sources

- Official vendor product documentation — At One Place (/about/)