WorksheetsPower & Efficiency
Total questions: 10
Worksheet time: 5mins
What is power measured in?
Joules (J)
Watts (W)
Kiliwatt-hours (kWh)
Volts (V)
How can you find the power of an appliance?
see how hot it gets when switched on
see what voltage it needs
look for the efficiency label
look for the power rating on the label
What type of diagram is used to show energy efficiency?
Bar chart
Sankey diagram
Flow chart
Power diagram
How do we calculate percentage efficiency?
(useful energy out ÷ total energy in) × 100
(useful energy in ÷ total energy out) x 100
(total energy out ÷ useful energy in) x 100
Calculate the efficiency of a bulb with an input energy of 50J, which outputs 40J of thermal energy and 10J of light energy.
10%
20%
25%
50%
Calculate the payback time in years of double glazing, which costs £2000 and saves you £40 a year.
2 years
5 years
40 years
50 years
You have used 784 kWh of electricity since your last meter reading. Each kWh costs 14p. Calculate the cost of your bill.
£56.00
£109.76
£560.00
£10976.00
Which kinds of appliances transfer the most energy?
heaters and cookers
lights
TVs and radios
computers
What does ‘payback time’ mean?
The time it takes to pay off the loan on a new appliance.
How long a new appliance will last without needing repairs.
The time it takes to save enough money on energy bills to pay for a change.
The time it takes a new appliance to reduce your energy bills.
Freezer A costs £200 and freezer B costs £150. Someone buying freezer A would save £20 per year on energy bills. What is the payback time if someone buys freezer A instead of B?
0.4 years
0.6 years
1.6 years
2.5 years
