If an electrical wire is accidentally stripped of its insulation, it is possible that the metal body of an electrical appliance will begin conducting electricity. One speaks of an insulation defect and the risk of electrocution is high for any person who touches the appliance.

For this reason, in all countries, the norms for electrical installations require that electrical appliances connected to the household current must also be connected to the earth. This connection must  present the lowest possible resistance so that current from the defect flows to the earth rather than taking any other path.