Types of electrical appliance
There are three main classes of electrical appliance, Class I, Class II & Double Insulated.
Depending on the class of the electrical appliance this would dictate the need for the appliance to be earthed.
Class I - Appliances with a metal casing such as a washing machine or brass bulb holder.
Class II - these have a plastic casing and may not be earthed such as a TV, or desk fan.
Double insulated - normally low voltage plastic cased appliances such as phone chargers. The plastic casing with any live parts being insulated twice in order to protect the user from touching them.
UK LAW in regards to electrical appliances
Under UK electrical regulations CLASS I appliances must be earthed. The job of the earth connection is to disconnect the power supply automatically if a fault develops in an appliance.
A internal fault such as a live wire coming lose could cause the metal casing of an appliance to become live, posing a serious risk of electric shock to any one who comes into contact with the appliance.
Read our page regarding earth continuity to learn more about what the earth connection does.
A major part of Portable Appliance Testing is to carry our an earth continuity test, to check that the earth connection is functioning properly to make sure the appliance is safe for use.