Flashcards in End Of Unit Questions Deck (12):
How may energy be wasted in an electrical heater?
As light from the glowing filament
How may energy be wasted in an electrical kettle?
Heating the body of the kettle itself and also possibly sound
How many kilowatts are equivalent to 30,000watts?
Which is more powerful, a 2000W hairdryer or a 2.2kW hairdryer?
What quantity is measured in kilojoules?
Energy is measured in kilojoules
An electrical light bulb transfers 6000J of energy in 1 minute. What is its power?
How much electrical energy in kWh is transferred when a 2kW iron is used for 30 minutes?
Why is the electrical energy supplied by the mains measured in kWh?
The joule is too small to be useful in this situation
A machine has an input power rating of 100kW and a useful power output of 40kW. What is its percentage efficiency?
Electricity costs 12p per kWh. What is the cost of using a 2.5 kW heater for 2 hours?
It costs 6.6p to use a 1.2kW microwave oven for 30 minutes. What is the cost per kWh of the energy supplied?