Earth Wire

There are three wires in a power circuit

• live wire which is the wire connected from the power source to the electrical appliance. Electricity flows from the power source to the electrical appliance through this wire. The live wire is brown in colour
• neutral wire which is the wire connected from the electrical source back to the power source. Electricity flows through this wire after the current flow through the electrical appliance and will flow back to the power source. The neutral wire is blue in colour
• earth wire which is the wire connected from the metal casing of electrical appliances to the ground. The earth wire is green in colour, with yellow stripes.

The earth wire, serving as a safety device, is connected to the ground. If there is a fault with the live wire, where the wire touches the metal casing of the electrical appliance, current will flow through the metal casing. If the earth wire is not installed in the electrical appliance and if someone touches the electrical appliance, the current will flow through their body and get electrocuted.

However, with the earth wire, connected to the metal casing of electrical appliance, if there is a fault in the live wire where it touches the metal casing, the current will flow through the metal casing and flow through the earth wire and the earth wire will transfer the current to the ground. Even if a person touches the metal casing, the current will still flow through the earth wire as it has a lower resistance and is easy to flow through. This protects people from getting electrocuted in case of a fault in the live wire

Switches

Switches are used to turn on and off an electrical appliance. A switch can be used as a safety device to cut the flow of current in the circuits in case of an accident where someone touches a live wire.

Two-way switches are used when two switches are used to control a single light bulb.

Lighting Circuits

Lightning circuits are installed with a 5A fuse because small current can light up a bulb. Lighting circuits also seldom carry more than 1A of current.
High powered appliances should never be used in lighting circuits as the high-powered appliances require larger current for it to operate. However, that large current could cause large heating which could melt the fuse and break the entire circuit

ELCB and MCB

 In our house, there is an Earth Leakage Circuit Breaker. This is like a main switch in the electrical circuit at home. When there is excessive current flowing through the wires at home, the Earth Leakage Circuit Breaker will break the entire circuit at home for a short time less than 25ms. This prevents excessive flow in the wires which can prevent overheating

The miniature circuit breaker operates like a fuse, but it can be manually reset without replacing it with another miniature circuit breaker. When there is an excessive current flow, the miniature circuit breaker will trip, breaking the circuit.

Fuse

A fuse is a safety device installed into plugs. It consists of a piece of tin-plated copper wire enclosed in a ceramic tube.

The thickness of the tin-plated copper wire determine how much current flow the fuse can withstand. When there is excessive current flow, the wire will melt, breaking the circuit which protects the wiring of the electrical device as well as to prevent overheating.
A fuse is chosen based on how much current flow is needed to operate the device normally. A fuse that can withstand a slightly larger amount of current compared to the current needed to operate the device normally is used. The most common fuse ratings are 3A, 5A, 10A, 13A and 15A
Example, if the device operates normally at a current of 4A, then a 5A fuse is used; if the device operates normally at 9A, then a 10A fuse is used.