Electrical hazards
Heating effect of current
- When a current passes through a resistor (or wire), energy is transferred to heat
- The temperature of the resistor (or wire) increases due to the collisions of the free electrons within the wire
- Some of the energy is dissipated into the surroundings by heating
The heating effect of current is used in many applications, such as electric hobs
Hazards of electrical systems
- Mains electricity can be dangerous if safety procedures are not followed
- Voltages as low as 50 V can pose a serious risk of electrocution
- Common electrical hazards include:
- damaged insulation
- overheating cables
- damp conditions
- excess current from overloading of plugs, extension leads, single and multiple sockets when using a mains supply
Electrical danger sign
The risk of electrocution is indicated by hazard signs but other risks which would not be signposted are listed below
Damaged insulation
- If the insulation around an electrical cable is damaged, the metal part of the wire may become exposed
- If a person touches the exposed wire, they could be subjected to a lethal electric shock
- There is also a chance that current will flow between the exposed wire and any piece of metal it comes into contact with
Overheating of cables
- If an excess of current flows in a wire, this can lead to overheating
- This could cause the insulation to melt, or even cause a fire
Damp conditions
- Damp conditions can be dangerous in the presence of electricity since water is an electrical conductor
- If moisture comes into contact with a live wire, this could set up
- a short circuit within the device, which could cause a fire
- a conductive path for current to flow through a person to the earth, which could cause electrocution
Excess current from overloading
- An excessive current may flow if too many plugs, extension leads or sockets are connected to the mains supply
- The heat created could cause the insulation to melt, or even cause a fire
Electrical fire due to excessive current
Too many appliances plugged into an extension lead can cause overheating and fire
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