ScienceAges 13-15

Percentage energy efficiency

Calculate the percentage efficiency of a device from useful energy output and total energy input. Review suitability for your learners before teaching.

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Age band:Ages 10-12 Ages 13-15

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Worksheet StudioPractice pack · Ages 13-15

Percentage energy efficiency

Take your time. Show your thinking.

1. A machine is supplied with 420 J of total energy and transfers 399 J as useful energy output. Calculate its percentage efficiency.
In: 420 J → Useful: 399 J · Wasted: 21 J
2. A machine is supplied with 40 J of total energy and transfers 38 J as useful energy output. Calculate its percentage efficiency.
In: 40 J → Useful: 38 J · Wasted: 2 J
3. A machine is supplied with 100 J of total energy and transfers 30 J as useful energy output. Calculate its percentage efficiency.
In: 100 J → Useful: 30 J · Wasted: 70 J
4. A machine is supplied with 340 J of total energy and transfers 119 J as useful energy output. Calculate its percentage efficiency.
In: 340 J → Useful: 119 J · Wasted: 221 J
5. A machine is supplied with 180 J of total energy and transfers 108 J as useful energy output. Calculate its percentage efficiency.
In: 180 J → Useful: 108 J · Wasted: 72 J
6. A machine is supplied with 240 J of total energy and transfers 84 J as useful energy output. Calculate its percentage efficiency.
In: 240 J → Useful: 84 J · Wasted: 156 J
7. A machine is supplied with 240 J of total energy and transfers 180 J as useful energy output. Calculate its percentage efficiency.
In: 240 J → Useful: 180 J · Wasted: 60 J
8. A machine is supplied with 40 J of total energy and transfers 18 J as useful energy output. Calculate its percentage efficiency.
In: 40 J → Useful: 18 J · Wasted: 22 J
9. A machine is supplied with 420 J of total energy and transfers 357 J as useful energy output. Calculate its percentage efficiency.
In: 420 J → Useful: 357 J · Wasted: 63 J
10. A machine is supplied with 260 J of total energy and transfers 195 J as useful energy output. Calculate its percentage efficiency.
In: 260 J → Useful: 195 J · Wasted: 65 J
11. A machine is supplied with 320 J of total energy and transfers 64 J as useful energy output. Calculate its percentage efficiency.
In: 320 J → Useful: 64 J · Wasted: 256 J
12. A machine is supplied with 460 J of total energy and transfers 345 J as useful energy output. Calculate its percentage efficiency.
In: 460 J → Useful: 345 J · Wasted: 115 J

12 questions · Seed 104729 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 13-15

Percentage energy efficiency

Answers and reasoning. Review before teaching.

1. A machine is supplied with 420 J of total energy and transfers 399 J as useful energy output. Calculate its percentage efficiency.
95%
Efficiency = (useful energy output ÷ total energy input) × 100% = (399 ÷ 420) × 100% = 95%.
2. A machine is supplied with 40 J of total energy and transfers 38 J as useful energy output. Calculate its percentage efficiency.
95%
Efficiency = (useful energy output ÷ total energy input) × 100% = (38 ÷ 40) × 100% = 95%.
3. A machine is supplied with 100 J of total energy and transfers 30 J as useful energy output. Calculate its percentage efficiency.
30%
Efficiency = (useful energy output ÷ total energy input) × 100% = (30 ÷ 100) × 100% = 30%.
4. A machine is supplied with 340 J of total energy and transfers 119 J as useful energy output. Calculate its percentage efficiency.
35%
Efficiency = (useful energy output ÷ total energy input) × 100% = (119 ÷ 340) × 100% = 35%.
5. A machine is supplied with 180 J of total energy and transfers 108 J as useful energy output. Calculate its percentage efficiency.
60%
Efficiency = (useful energy output ÷ total energy input) × 100% = (108 ÷ 180) × 100% = 60%.
6. A machine is supplied with 240 J of total energy and transfers 84 J as useful energy output. Calculate its percentage efficiency.
35%
Efficiency = (useful energy output ÷ total energy input) × 100% = (84 ÷ 240) × 100% = 35%.
7. A machine is supplied with 240 J of total energy and transfers 180 J as useful energy output. Calculate its percentage efficiency.
75%
Efficiency = (useful energy output ÷ total energy input) × 100% = (180 ÷ 240) × 100% = 75%.
8. A machine is supplied with 40 J of total energy and transfers 18 J as useful energy output. Calculate its percentage efficiency.
45%
Efficiency = (useful energy output ÷ total energy input) × 100% = (18 ÷ 40) × 100% = 45%.
9. A machine is supplied with 420 J of total energy and transfers 357 J as useful energy output. Calculate its percentage efficiency.
85%
Efficiency = (useful energy output ÷ total energy input) × 100% = (357 ÷ 420) × 100% = 85%.
10. A machine is supplied with 260 J of total energy and transfers 195 J as useful energy output. Calculate its percentage efficiency.
75%
Efficiency = (useful energy output ÷ total energy input) × 100% = (195 ÷ 260) × 100% = 75%.
11. A machine is supplied with 320 J of total energy and transfers 64 J as useful energy output. Calculate its percentage efficiency.
20%
Efficiency = (useful energy output ÷ total energy input) × 100% = (64 ÷ 320) × 100% = 20%.
12. A machine is supplied with 460 J of total energy and transfers 345 J as useful energy output. Calculate its percentage efficiency.
75%
Efficiency = (useful energy output ÷ total energy input) × 100% = (345 ÷ 460) × 100% = 75%.

12 questions · Seed 104729 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Percentage energy efficiency

Take your time. Show your thinking.

1. A machine is supplied with 420 J of total energy and transfers 399 J as useful energy output. Calculate its percentage efficiency.
In: 420 J → Useful: 399 J · Wasted: 21 J
2. A machine is supplied with 40 J of total energy and transfers 38 J as useful energy output. Calculate its percentage efficiency.
In: 40 J → Useful: 38 J · Wasted: 2 J
3. A machine is supplied with 100 J of total energy and transfers 30 J as useful energy output. Calculate its percentage efficiency.
In: 100 J → Useful: 30 J · Wasted: 70 J
4. A machine is supplied with 340 J of total energy and transfers 119 J as useful energy output. Calculate its percentage efficiency.
In: 340 J → Useful: 119 J · Wasted: 221 J
5. A machine is supplied with 180 J of total energy and transfers 108 J as useful energy output. Calculate its percentage efficiency.
In: 180 J → Useful: 108 J · Wasted: 72 J
6. A machine is supplied with 240 J of total energy and transfers 84 J as useful energy output. Calculate its percentage efficiency.
In: 240 J → Useful: 84 J · Wasted: 156 J
7. A machine is supplied with 240 J of total energy and transfers 180 J as useful energy output. Calculate its percentage efficiency.
In: 240 J → Useful: 180 J · Wasted: 60 J
8. A machine is supplied with 40 J of total energy and transfers 18 J as useful energy output. Calculate its percentage efficiency.
In: 40 J → Useful: 18 J · Wasted: 22 J
9. A machine is supplied with 420 J of total energy and transfers 357 J as useful energy output. Calculate its percentage efficiency.
In: 420 J → Useful: 357 J · Wasted: 63 J
10. A machine is supplied with 260 J of total energy and transfers 195 J as useful energy output. Calculate its percentage efficiency.
In: 260 J → Useful: 195 J · Wasted: 65 J
11. A machine is supplied with 320 J of total energy and transfers 64 J as useful energy output. Calculate its percentage efficiency.
In: 320 J → Useful: 64 J · Wasted: 256 J
12. A machine is supplied with 460 J of total energy and transfers 345 J as useful energy output. Calculate its percentage efficiency.
In: 460 J → Useful: 345 J · Wasted: 115 J

12 questions · Seed 104729 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Percentage energy efficiency

Answers and reasoning. Review before teaching.

1. A machine is supplied with 420 J of total energy and transfers 399 J as useful energy output. Calculate its percentage efficiency.
95%
Efficiency = (useful energy output ÷ total energy input) × 100% = (399 ÷ 420) × 100% = 95%.
2. A machine is supplied with 40 J of total energy and transfers 38 J as useful energy output. Calculate its percentage efficiency.
95%
Efficiency = (useful energy output ÷ total energy input) × 100% = (38 ÷ 40) × 100% = 95%.
3. A machine is supplied with 100 J of total energy and transfers 30 J as useful energy output. Calculate its percentage efficiency.
30%
Efficiency = (useful energy output ÷ total energy input) × 100% = (30 ÷ 100) × 100% = 30%.
4. A machine is supplied with 340 J of total energy and transfers 119 J as useful energy output. Calculate its percentage efficiency.
35%
Efficiency = (useful energy output ÷ total energy input) × 100% = (119 ÷ 340) × 100% = 35%.
5. A machine is supplied with 180 J of total energy and transfers 108 J as useful energy output. Calculate its percentage efficiency.
60%
Efficiency = (useful energy output ÷ total energy input) × 100% = (108 ÷ 180) × 100% = 60%.
6. A machine is supplied with 240 J of total energy and transfers 84 J as useful energy output. Calculate its percentage efficiency.
35%
Efficiency = (useful energy output ÷ total energy input) × 100% = (84 ÷ 240) × 100% = 35%.
7. A machine is supplied with 240 J of total energy and transfers 180 J as useful energy output. Calculate its percentage efficiency.
75%
Efficiency = (useful energy output ÷ total energy input) × 100% = (180 ÷ 240) × 100% = 75%.
8. A machine is supplied with 40 J of total energy and transfers 18 J as useful energy output. Calculate its percentage efficiency.
45%
Efficiency = (useful energy output ÷ total energy input) × 100% = (18 ÷ 40) × 100% = 45%.
9. A machine is supplied with 420 J of total energy and transfers 357 J as useful energy output. Calculate its percentage efficiency.
85%
Efficiency = (useful energy output ÷ total energy input) × 100% = (357 ÷ 420) × 100% = 85%.
10. A machine is supplied with 260 J of total energy and transfers 195 J as useful energy output. Calculate its percentage efficiency.
75%
Efficiency = (useful energy output ÷ total energy input) × 100% = (195 ÷ 260) × 100% = 75%.
11. A machine is supplied with 320 J of total energy and transfers 64 J as useful energy output. Calculate its percentage efficiency.
20%
Efficiency = (useful energy output ÷ total energy input) × 100% = (64 ÷ 320) × 100% = 20%.
12. A machine is supplied with 460 J of total energy and transfers 345 J as useful energy output. Calculate its percentage efficiency.
75%
Efficiency = (useful energy output ÷ total energy input) × 100% = (345 ÷ 460) × 100% = 75%.

12 questions · Seed 104729 · Age guidance, not curriculum certification