P2.7 Energy and power Flashcards
What is a power rating?
The power rating is the number in watts or kilowatts that tells you the rate at which an appliance transfers energy.
What is a watt?
A watt is the unit of power, symbol W
What is a kilowatt?
1 kilowatt = 1000 watts, symbol kW
What is a kilowatt hour?
Kilowatt hours is the unit of energy used by electricity companies, symbol kWh
What is the equation to calculate power?
The energy to calculate power is:
Power (W) = Energy (J)/Time(S)
When you pay an electricity bill, what are you paying for?
When you are paying an electricity bill, you are paying for a fuel, such as coal to be burnt in a power station.
What does the power station generate by burning fuels?
The power station generates the potential difference that we call ‘mains electricity’.
What are you charged for by using an appliance?
You are charged for the number of hours that you use each appliance, and for the power of the appliance.
What can you calculate energy use in?
You can calculate energy use in Joules or Kilowatt hours.
What could you do to reduce your bills?
To reduce your energy bills you could: * use fewer appliances * use appliances that require less power to produce the same output * use the appliance for fewer hours
What is the equation to work out energy using kilowatt hours?
energy (kWh) = power (kW) × time (h)
To find the cost of electricity you need to use kilowatts (kW) as the unit for power and hours (h) for time.
Why does insulation reduce the rate at which you need to supply energy to heat the house?
Insulation reduces the rate at which energy is transferred to the surroundings, so insulation reduce the rate at which you need to supply energy to heat the house.
What is the equation for power and components?
Power (W) = Potential difference(V) x Current A)
What is the equation of calculating the cost of electricity?
Cost of electricity = Power(kW) x time(h) x cost per unit (p)
