domestic electricity

What unit is used to measure energy used in the home?

Kilowatt hours (kWh), also known as Units.

How is 1 kWh defined?

It is the energy converted by a 1 kW device for 1 hour.

What is the formula to calculate the units used in kWh?

Units used (kWh) = Power (kW) x time (hours).

How do you calculate the cost of electricity used?

Cost = Units used × Cost per unit.

What is the importance of converting between units in electricity calculations?

Power is often given in Watts and time in seconds or minutes, requiring conversion for accurate calculations.

What does a higher efficiency rating indicate about a device?

It indicates that the device is more efficient, which helps compare devices that perform the same function.

What are the two types of current electricity can be supplied in?

Alternating Current (AC) and Direct Current (DC).

What is the characteristic of Alternating Current (AC)?

Voltage constantly changes size and current constantly changes direction; supplied by the National Grid.

What is the characteristic of Direct Current (DC)?

Voltage and current have a constant size and direction; supplied by batteries.

What is a ring main circuit?

It is a type of electrical circuit in homes that allows current to travel two ways, enabling thinner wires and lower current.

What are the three wires in a ring main circuit?

Live, Earth, and Neutral.

What does the live wire do in a ring main circuit?

It carries a current into the house at a high voltage.

What is the purpose of the earth wire?

It carries no current under normal operation and protects users from electric shock by directing fault current safely to the ground.

What happens if the live wire touches the casing of a device?

The current will travel safely to the earth through the earth wire rather than through a person.

What is the function of a fuse in an electrical circuit?

It stops the current if it becomes too large by melting a wire, which requires replacement once it 'blows'.

What is a Miniature Circuit Breaker (MCB)?

A safety device that stops the current if it becomes too large and can be reset.

What is the function of a Residual Current Circuit Breaker (RCCB)?

It stops the current if there is a difference between the current in the neutral and live wires, protecting users from electric shock.

How quickly does an RCCB react to a fault?

It reacts to a very small difference and very quickly, and can be reset.

What is the voltage supplied in a typical home circuit?

230V.

What is the advantage of using a ring main circuit for sockets?

You can add more sockets anywhere on the ring, and each will have the same voltage.

What is the significance of the current being the same in the live and neutral wires during normal operation?

It ensures that the circuit is functioning correctly.

if the power a microwave oven is 850 watts for a total of 30 mins, calculate the cost of electricity it uses if each unit (kWh) costs 12p

Units used = P (kW) x t (h) = 0.85 x 0.5

Cost = 0.425 x 12p = 5.1p