Power and Efficiency
Task 1: Answer the following questions
1. What is the unit for energy?
2. Energy used per second is measured in watts. How many watts are there in a kilowatt?
Task 2: Look at the following objects, underneath each appliance identify the useful energy
transfer and one way energy might be wasted.
Useful
Wasted
Task 3: Complete the diagram to show the energy transfer that occurs when a car uses its
fuel to move.
Task 4: Complete the table to show the energy transfers in the 4 objects.
Task 5: Calculate the energy efficiency of the washing machine as a percentage.
A washing machine uses 3000 Joules of energy.
500 Joules is transformed from electrical energy
into sound. 25 Joules is transformed into light
energy. The rest of the energy is used usefully.
Answer:
Task 6: Use the Sankey diagrams below to explain which light bulb is the most efficient.
Answer: