Damaged insulation exposes conducting wire to the air, which can cause a short-circuit if two exposed wires touch, or an electric shock if sufficient current contacts a human
Overheating of cables can cause the insulation to melt, releasing toxic fumes, or a fire
Damp conditions are dangerous because water is an electric conductor and touching an electrical appliance with wet hands can cause an electric shock
Precautions
Fuses
Fuses are thin wires that melt and break above a certain current, preventing the current getting too high in the circuit; fuses are contained in cartridges, making them easy to replace
The fuse amperage required can be calculated from the power rating of the device and the mains voltage value of 230 V
Circuit breakers
Circuit breakers are switches that turn off above a certain current and can be turned on again
It consists of a switch and an electromagnet: when a large current flows through the circuit, the induced magnetism causes the switch to open, breaking the circuit