Electricity: Electricity in the Home

Domestic Use of Electricity

• The UK mains supply has a frequency of 50 Hz and is about 230 volts for most homes.

• Alternating current (AC) is used in homes because it can easily be stepped up or down in voltage by transformers.

• Plug sockets in the home are connected in parallel. This means each appliance receives the full mains voltage and can be independently controlled.

• Objects in the home that use electricity are referred to as electrical appliances. They are designed to transfer electrical energy into useful energy forms such as heat, light, sound, or kinetic energy.

• Most electrical charges are caused by friction – the transfer of electrons from one material to another.

Safety Features in Electrical Appliances

• Electrical appliances have safety features to protect the user including fuses, circuit breakers and earth wires.

• Fuses contain a thin wire that melts and breaks if the current is greater than the fuse rating, breaking the circuit and protecting the device.

• Circuit Breakers work in a similar way to fuses, but can be reset by simply flipping the switch back, whereas a fuse has to be replaced.

• The earth wire creates a safe route for the current to flow through if something goes wrong with the appliance, it’s usually connected to the metal casing of an appliance.

• The live wire is brown, the neutral wire is blue, and the earth wire is striped green and yellow.

Energy and Power in Electrical Systems

• The power (P) drawn by an electrical device is the product of the voltage (V) applied across its terminals, and the current (I) passing through it. The formula is P = VI.

• Power is measured in watts (W), where 1 watt = 1 joule of energy transferred per second.

• The energy transferred by a device can be calculated by multiplying the power of the device by the time it has been on for. The formula is Energy = Power x Time.

• The kilowatt-hour (kWh) is a unit of energy typically used for billing domestic electricity usage.

• To calculate the number of kilowatt-hours of electricity used, multiply the power of the appliance in kW by the time the appliance is used for in hours.

Understanding these concepts is crucial for understanding how electricity is used and handled safely in the home.