The Dangers of Mains Electricity

There is always a potential for danger when dealing with electricity. We call a sudden increase in current a surge. This can be caused by a range of factors, such as a faulty appliance, bad wiring, lightning strikes and many more factors. Surges can lead to fires or electric shocks.

Built-in safety measures, such as fuses and earth wires, reduce the risk of such damage. Both fuses and earth wires act in a similar way, breaking the circuit when the current gets too high.

Fuses

A fuse contains a thin piece of wire which is connected to the live wire. When there is a surge, the high current will flow through the fuse. As the wire is very thin, it heats up quickly, which causes the wire to melt. Once the wire melts, the circuit breaks, which means that no more current can flow.

Fuses come in little cases with a thin wire inside.

Fuses have different ratings, which indicate the current level at which they will break the circuit.

For example:

  • A 5 amp fuse will break the circuit when there is a surge that raises the current above 5 amps
  • A 10 amp fuse will break the circuit when there is a surge that raises the current above 10 amps

This meant that for a 5-amp appliance, you should use a fuse rated slightly above 5 amps so that the appliance operates safely without causing the fuse to blow.

Advantages and disadvantages of using fuses

Advantages

  • The cheapest form of protection in an electrical circuit
  • Relatively simple and easy to use
  • Do not require maintenance
  • Easy to remove and replace without touching a live wire

Disadvantages

  • Fuses are permanently broken after a surge melts the wire, which means that they need to be replaced before the circuit can work again.
  • Fuses have a one-time use, whereas circuit breakers can be reused multiple times.

Earthing

There can be an electrical fault in the circuit, for example, if the live wire loosens and touches the casing. If a person touches the casing, they will receive a huge electric shock. To prevent this, the earth wire gives the current an alternative path to flow. However, this also prevents the appliance from operating.

The earth wire is made of copper, which means that it provides a low-resistance pathway for the electric current. This current is directed into the ground. So, instead of passing through the human, it follows a different pathway into the ground.

Circuit Breakers

Like fuses, circuit breakers break the circuit when the current exceeds a certain level. However, circuit breakers are electrical switches that do not get permanently damaged when they break the circuit.

Instead, they turn off once they get tripped. So, the circuit breaker can easily be reset instead of needing to be replaced.

Advantages and disadvantages of using circuit breakers

Advantages

  • Unlike fuses, circuit breakers do not need to be replaced after they break the circuit. Instead, they can easily be reset.
  • In some cases, the current is not large enough to melt the fuse, but it can still harm the person using the electrical appliance. In these cases, using a circuit breaker instead of a fuse will provide better protection.
  • Circuit breakers can respond faster than fuses.

Disadvantages

  • Circuit breakers are more expensive to install, repair and replace than fuses.
  • They can be overly sensitive and trip for reasons unrelated to electrical overloads.

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