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Syllabus Dot Point
electrical safety
Fuse Boxes
Fuse boxes contain safety devices called fuses or circuit breakers which are designed to prevent an excess of electric current entering your house by only allowing a certain maximum current to flow in. When the electrical current is too large, an electromagnet attracts a spring loaded switch which breaks the circuit and cuts the power supply. The switch must be reset before any current can flow again.
Safety tip: Circuit breakers and fuses prevent electrical fires and overheating that can be caused by an overload of electrical current.
Household Circuits
Circuits in houses are generally wired in parallel, which allows you to operate each light or power point independently of the others. This also means the current running through any one section of the parallel circuit stays small enough to prevent problems because in parallel circuits the current is split up and travels along each separate path.
Safety tip: When you use a power board or double adaptor, each device plugged in creates a new parallel circuit, but the total current for all of the devices must flow in the one house circuit. The current drawn by multiple devices in the circuit means that it is possible to exceed the maximum current draw allowed by the circuit fuse or circuit breaker. If the fuse or circuit breaker fails to operate then this can cause wires to overheat because even good conductors do provide some resistance to electric currents. This is why it can be very dangerous to piggyback double adaptors or to plug too many devices into a single power point. Usually, but not always, power boards have their own built in circuit breaker.
Other safety devices used in household circuits
Safety Switches or Residual Current Device (RCD) – This is your lifeline against electric shock which is usually kept in the fuse box alongside a circuit breaker or fuse. Mainly known as safety switches in Australia but sometimes called RCD, these safety devices detect leaking current from faulty switches, wiring or electrical appliances. If it detects a problem that could put you at risk, it will turn the power off within 0.03 of a second. Each safety switch has a ‘test’ button, so it’s important that they are tested every couple of months.
Earth wires – Earth wires are designed to protect you from electric shock. They are attached to power points which join to a main earth wire, which is attached to a metal pipe and/or special metal electrode (metal stake) driven into the ground. The idea is that the electricity is given a more conductive path to the earth rather than through a person.
Surge diverter – These protect your personal appliances from voltage surges such as those resulting from a lightning strike. They do not protect people from electric shock. The surge diverter captures the voltage spikes in the wiring within the unit itself. This stops the voltage spike from transferring into your appliance and damaging it.
Earth spike C Block "The Entrance Campus"
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