This post is about Practical Electricity – Safety devices and Common Electrical Hazards.
Common Electrical Hazards
Damaged Insulation – If the plastic covering of a wire is damaged, the exposed wire can give a severe electric shock if touched.
Overheating of Cables – When too much current flows through a wire that is too thin, or if a long wire is tightly coiled, the wire can overheat. This may cause a fire or melt the insulation, exposing live wires.
Damp Conditions – Water can conduct electricity. If moisture comes into contact with live wires, it can cause a short circuit, which may lead to a fire or increase the risk of electrocution.
Overloading of Plugs and Sockets – Plugging too many devices into an extension cord, multi-plug adapter, or power socket can cause excessive current flow. This generates heat, which may result in a fire.
Electrical Safety Measures
Insulation & Double Insulation
The conducting part of a wire is usually made of copper or another metal.
If exposed, it can cause electric shocks when touched.
To prevent this, wires are covered with an insulating material like rubber or plastic.
Double insulated appliances are designed so that the live wires cannot touch the metal casing. These appliances do not require an earth wire.
Earthing
Many electrical appliances have metal casings, which can become dangerous if a live wire inside touches the casing.
If this happens, the casing would become live, posing an electrocution risk.
The earth wire acts as a safety feature:
– It provides a low-resistance path to the ground.
– A large current flows through the earth wire, and also through the live wire.
– This high current causes the fuse to melt and break the circuit.
– This cuts off electricity to the appliance, making it safe.
Fuses & Circuit Breakers (Trip Switches)
Fuses are safety devices that stop the flow of electricity if the current becomes too high (due to a fault or power surge).
A fuse consists of a thin wire inside a glass cylinder.
If the current is too large:
– The wire heats up and melts.
– This breaks the circuit, stopping the current.
Trip switches (circuit breakers) in the consumer unit (where electricity enters a building) perform the same function:
– If the current is too high, the switch trips (automatically turns off).
– This stops the current flow, preventing damage or fire.
Choosing the Correct Fuse
Fuses come in different ratings, commonly 3A, 5A, and 13A.
To select the right fuse, we calculate the required current using: I = P/V.
Where:
I = Current (A)
P = Power of the appliance (W)
V = Voltage (V)
The fuse rating should be slightly higher than the calculated current but not too high, to ensure protection.
That’s it!
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