Question

To which wire of a cable in a power circuit should the metal case of a geyser be connected?

Answer 1

The term earthing, which is also denoted as grounding, is based on research that demonstrates that connecting to Earth's electrical energy encourages physical welfare. The act of Earthing denotes a physical connection between the electrical frequencies of the human body with that of Earth.

Complete answer:
Earthing is used to safeguard us from an electric shock. It safeguards the electrical circuit and the living beings by laying out a path (that is a protective conductor) for a reproach current to flow to earth. It also generates the protective device (that is either a circuit-breaker or fuse) to switch off the electric current to the circuit that has the reproach.
The earth wire colour is characterized as green and yellow stripes, that is in in line with the IEC that is the International Electrical Commission’s regulations. It has the key safety function of connecting the metal casing of the geyser of electrical appliances with the ground.

Therefore, the metal case of a geyser must be connected to the green wire, which is an earthed wire, of the cable in a power circuit.

Note: If a house or a factory or a power line is not earthed, people could get electrocuted. Without an earth connection, the safety switches will not work and an electrical fault could cause a house or a factory or a power line to become 'live' as the current flows to earth.