11th grade Compare devices that change energy from one form to another worksheet

Compare devices that change energy from one form to another

Grade 11 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Ari's generator runs on 5000 J of fuel. The engine is 30% efficient, the generator 90% and the lamp 80%. How much light energy comes out?
2. 2.

   Bo's generator runs on 800 J of fuel. The engine is 20% efficient, the generator 85% and the lamp 40%. How much light energy comes out?

3. Read this first

   Three small wind turbines (example data)

   design	energy in (J)	electrical out (J)	mass (g)	cost ($)
   A	400	120	600	24
   B	500	160	900	30
   C	300	105	450	45

4. 3.

   Using the turbine table, which design is the most efficient, and by how much, Jun?

   • B, at 32%, since it gives the most electrical energy
   • A, at 30%, since it has the lowest cost
   • C, at 105%, its electrical energy as a percent
   • C, at 35%
5. 4.

   Using the turbine table, the turbine must weigh at most 700 g and cost at most $40. Which design qualifies, and how efficient is it, Kira?

   • A and B, since both cost under $40
   • Only A qualifies, at 30%
   • C, since it is the most efficient
   • B, since it gives the most electrical energy
6. 5.

   A 750 W motor is 85% efficient and runs 4.0 h. How much energy does it waste, Milo?

   • 3,000 Wh, the energy put in
   • 450 Wh
   • 2,550 Wh, the useful energy
   • 112.5 Wh, one hour of the waste
7. 6.

   A pump must lift 60 kg of water each second through 5.0 m. It is 60% efficient. What input power does it need, Noah?

   • 2,940 W, the useful power
   • 4,900 W
   • 490 W
   • 1,764 W, from 2,940 × 0.60
8. 7.

   An electric car stores 60 kWh. Its motor is 90% efficient and its wheels need 0.18 kWh per km. What is its range, Pia?

   • About 333 km, leaving out the motor loss
   • About 270 km, taking 90% of 300 km
   • About 300 km
   • About 370 km, from 60 ÷ (0.18 × 0.90)
9. 8.

   Kettle A is 90% efficient at 1,800 W; kettle B is 85% efficient at 2,400 W. Which heats 1.0 kg of water by 80 °C (334,880 J) in under 3 min, Ren?

   • Only B, in about 164 s
   • A, since it is more efficient
   • Neither, since both take over 3 minutes
   • Both, since both are over 85% efficient
10. 9.

    A 1,200 kg car slows from 20 m/s to rest. Regenerative braking recovers 60% of its kinetic energy. How much is recovered, Tala?

    • 144 kJ
    • 240 kJ, the whole of the kinetic energy
    • 288 kJ, using mv² without the one half
    • 96 kJ, 40% of the kinetic energy
11. 10.

    Sunlight gives 1,000 W per m². A solar panel is 20% efficient. What area gives 1,200 W, Zee?

    • 6.0 m²
    • 1.2 m², leaving out the efficiency
    • 0.24 m², multiplying by 0.20
    • 30 m², using 4% efficiency