3. A description and explanation of the function of circuit breakers, fuses, earthing and double insulation and one other safety device commonly used in the home.
Circuit Breakers:
A circuit breaker prevents a circuit from overloading. It works by continuously measuring the current in a circuit and if it rises above the maximum current it is able to carry safely, an electromagnet breaks the circuit and halts the flow; stopping the circuit from being overloaded. The circuit breaker can be reset and the circuit restored after it has been set off.
Fuses:
A fuse like a circuit breaker is used to prevent a household circuit from overloading. A fuse uses is a resistance wire with a low melting point connected in series into a circuit, meaning the total current of the circuit must pass through it. As the fuse is a resistor it generates heat faster than the rest of the circuit. The fuse has a melting point that is in correlation to the maximum current the circuit can carry, so when the current rises above the circuit’s maximum the fuse will become hot and then melts, breaking the circuit an removing the chance of the circuit being overloaded. Fuses are made with different melting points allowing different strengths of current to flow through it making it practical for all household circuits. The fuses are inside an insulated casing (usually rubber) to prevent the melted fuse becoming a hazard. The disadvantage of the fuse is that once the wire is melted it is unusable and must be replaced for the flow of electricity in the circuit to be restored.
Earthing:
Earthing or an earth wire is fitted in order to protect people from an electric shock from electrical appliances. An earth wire is a good conductor and connects the neutral wire in the fuse box and the individual power outlets in the house to the earth. When something comes into direct contact with an active wire or an object with a live current and there is no earthing wire the person would receive an electric shock from the current that runs through their body to the ground. If an earthing wire were to be in place then rather than the current flowing through the body it travels down the better conducting earth wire to the ground. The current traveling down the earth wire also simultaneously sets off the fuse or circuit breaker, stopping the current.
Double insulation:
Double insulation is another means of protecting people from the current that flows through an appliance. All the electrical wiring in a house is insulated by a layer of rubber or plastic so that the bare wire is not exposed. In many of these appliances there is another second layer of insulation as a buffer incase the first layer fails. This second layer of insulation ensures the electrical wiring is safe to handle and cuts out the chance of a person receiving an electric shock.
Residual Current Device:
A Residual Current Device (RCD) is used to prevent household circuits leaking current. The device is used to detect if any current flows from the circuit to the earth through a person or through other means, and then break the circuit to stop the current flowing before it causes any harm or dangerous electric shock. A RCD greatly reduces the risk of electric shock from a leaking circuit however it is not guaranteed to provide protection every time. It is also called a safety switch and must be installed in any new buildings as standard fuse box equipment.
A circuit breaker prevents a circuit from overloading. It works by continuously measuring the current in a circuit and if it rises above the maximum current it is able to carry safely, an electromagnet breaks the circuit and halts the flow; stopping the circuit from being overloaded. The circuit breaker can be reset and the circuit restored after it has been set off.
Fuses:
A fuse like a circuit breaker is used to prevent a household circuit from overloading. A fuse uses is a resistance wire with a low melting point connected in series into a circuit, meaning the total current of the circuit must pass through it. As the fuse is a resistor it generates heat faster than the rest of the circuit. The fuse has a melting point that is in correlation to the maximum current the circuit can carry, so when the current rises above the circuit’s maximum the fuse will become hot and then melts, breaking the circuit an removing the chance of the circuit being overloaded. Fuses are made with different melting points allowing different strengths of current to flow through it making it practical for all household circuits. The fuses are inside an insulated casing (usually rubber) to prevent the melted fuse becoming a hazard. The disadvantage of the fuse is that once the wire is melted it is unusable and must be replaced for the flow of electricity in the circuit to be restored.
Earthing:
Earthing or an earth wire is fitted in order to protect people from an electric shock from electrical appliances. An earth wire is a good conductor and connects the neutral wire in the fuse box and the individual power outlets in the house to the earth. When something comes into direct contact with an active wire or an object with a live current and there is no earthing wire the person would receive an electric shock from the current that runs through their body to the ground. If an earthing wire were to be in place then rather than the current flowing through the body it travels down the better conducting earth wire to the ground. The current traveling down the earth wire also simultaneously sets off the fuse or circuit breaker, stopping the current.
Double insulation:
Double insulation is another means of protecting people from the current that flows through an appliance. All the electrical wiring in a house is insulated by a layer of rubber or plastic so that the bare wire is not exposed. In many of these appliances there is another second layer of insulation as a buffer incase the first layer fails. This second layer of insulation ensures the electrical wiring is safe to handle and cuts out the chance of a person receiving an electric shock.
Residual Current Device:
A Residual Current Device (RCD) is used to prevent household circuits leaking current. The device is used to detect if any current flows from the circuit to the earth through a person or through other means, and then break the circuit to stop the current flowing before it causes any harm or dangerous electric shock. A RCD greatly reduces the risk of electric shock from a leaking circuit however it is not guaranteed to provide protection every time. It is also called a safety switch and must be installed in any new buildings as standard fuse box equipment.