We use many electrical appliances in our houses, college, offices like a fan, heater, refrigerator, charger, vacuum cleaner, etc. Electrical Appliances are divided into certain classes according to the IEC 61140 standard and used to differentiate between the protective-earth connection requirements of devices. These are Class 0, Class I, Class II, and Class III.
Fig. Class II Appliance

Electrical Appliance Classes

(a) Class 0
Class 0 appliances have no protective earth connection. They feature only a single level of insulation between live parts and exposed metalwork. The sales of such items have been prohibited in much of the world on safety grounds.
(b) Class I

Class I appliances must have their chassis connected to electrical earth i.e. connected to the ground, by a separate earth conductor. The earth or ground connection is achieved with a 3-conductor mains cable, typically ending with 3-prong AC connector which plugs into a corresponding AC outlet. The symbol for class I appliances is shown above.

(c) Class II
A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth (ground). The symbol for class II appliances is shown above.
(d) Class III

This appliance is designed to be supplied with a separated/safety extra-low voltage (SELV) power source. The voltage from a SELV supply is low enough that under normal conditions a person can safely come into contact with it without risk of electrical shock. The symbol for class III appliances is shown above.
Electrical Appliance Classes

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