For the exam you will need to remember that:
1 Watt = 1 Joule per second or 1 j/s
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A more powerful kettle transfers more electrical energy into heat energy every second, so the water should boil quicker. This is because the greater the power of a device the faster it transfers energy from one form to another
eg a 2 watt kettle transfers 2 j/s whereas a 5 watt kettle will transfer 5 j/s (More energy is transferred because there is more to start with)
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