Name the unit of electrical energy that companies supplying electricity use to bill their consumers - Junior Cycle Science - Question d - 2010

To calculate the cost of using the electric kettle:

1. Identify the power rating of the kettle: The kettle has a power rating of 3 kW.

2. Calculate the energy consumption in kWh: The kettles are used for 10 hours, so the energy consumed is:

   $$ext{Energy (kWh)} = ext{Power (kW)} imes ext{Time (hours)} = 3 ext{ kW} imes 10 ext{ hours} = 30 ext{ kWh}$$

3. Calculate the cost: Given that each unit costs 15 cents:

   $$ext{Cost} = ext{Energy (kWh)} imes ext{Cost per unit} = 30 ext{ kWh} imes 0.15 ext{ EUR} = 4.5 ext{ EUR}$$

So, the cost of using the kettle for 10 hours is 4.5 EUR.