Double Insulation

Double Insulation

An electrical appliance which is double insulated does not have an earth wire fitted. The appliance is designed in such a way that the electrical parts can never come into contact with the outer casing of the device. Common double insulated appliances are hair dryers, radios and cassette players.

A wet double insulated appliance is exceptionally dangerous - water is a good conductor of electricity and will easily reach the live electrical components within the case. Any human user touching the casing will then receive an electric shock. It is important to note that the human conductivity is increased when hands are wet, allowing a greater current to flow through the casualty.

For this reason, do not operate a mains radio, hairdryer or double insulated appliance in any wet area - especially a bathroom

Do not touch any person who has been electrocuted until you are sure that the electricity supply has been shut off.

Taken from:http://www.users.zetnet.co.uk/computing/MainPage/SecDepts/Physics/Resources/Glossary/DoubleIns.html