Explain the function of earth wire. Why is it necessary to earth metallic appliances?

to prevent any electric shock to the user. (more info below)

Explanation:

The metallic structure of electrical equipment is bound to the earth by means of earth wire, such that any electrical current leakage is transmitted to the field. This stops the consumer from experiencing any electrical shocks. That's why the electrical devices ought to be earthed.

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an ion is a charged atom or molecule. it is charged because the number of electrons do not equal the number of protons in the atom or molecule. an atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.