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

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Compare devices that change energy from one form to another

Grade 11 Science Worksheet - Challenge Me

NameDate

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

  1. Ari's hand-crank chain has stages of 25%, 80% and 90% efficiency. To store 450 J in a battery, how much work must go in?

  2. Bo's hand-crank chain has stages of 40%, 88% and 50% efficiency. To store 2200 J in a battery, how much work must go in?

  3. Esme's hand-crank chain has stages of 21%, 80% and 50% efficiency. To store 840 J in a battery, how much work must go in?

  4. A plant is 36% efficient, the grid delivers 94% and the motor is 90% efficient. About how much of the fuel energy does useful work, Kira?

    • About 36%, the plant alone
    • About 30%
    • About 73%, the average of the three
    • About 3.0%

  5. From 100 units of fuel, a plant makes 30 units of electricity and 45 units of useful heat for homes. What share of the fuel is put to use, Luz?

    • 30%, counting the electricity alone
    • 75%, counting heat and electricity
    • 45%, counting the heat alone
    • 25%, the share that is wasted

  6. An ad says "our electric heater is 100% efficient, so it wastes nothing." Most electricity comes from plants near 35%. Judge the claim, Milo.

    • False: the heater converts nothing into heat as it runs
    • True at the heater, but 65% of the fuel energy was lost earlier
    • True: no energy is lost anywhere upstream of the heater
    • False: the heater itself wastes most of the energy it uses

  7. Noah wants to compare the efficiency of two motors. Which measurements are best?

    • Each motor's top speed while it spins with no load
    • Electrical energy in and work done on one load, for each
    • The wattage printed on each motor's label plate
    • How hot each motor gets after running for one minute

  8. A battery pack is rated 95% round-trip. A test charges it with 500 Wh and gets 440 Wh back. Judge the rating, Pia.

    • The test shows 88%, which is close enough to 95%
    • The test shows 95%, since 440 + 60 = 500
    • The test shows 12%, so the rating is far off
    • The test shows 88%, 7 points below the rating

  9. Engine X goes from 40% to 50% efficiency; engine Y goes from 80% to 90%. For 100 J of useful work, which saves more fuel energy, Tala?

    • Both save the same, since each gains 10 points
    • Engine Y saves about 50 J; engine X saves about 14 J
    • Engine X saves about 50 J; engine Y saves about 14 J
    • Engine Y saves more, since it is closer to 100%

  10. Zee wants to find where a toy robot wastes the most energy. Which test is best?

    • Measure the energy in and out of each stage
    • Replace the parts with new ones at once
    • Run the robot for longer and watch the battery
    • Measure the energy in and the final speed alone
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11th grade Compare devices that change energy from one form to another worksheet – printable
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About this worksheet

Compare devices that change energy from one form to another. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can find efficiency from powers (useful power m g h ÷ t over input power), and complete an energy balance from bars.
  • I can multiply efficiencies along a chain and work backwards from a target output, and find range, input power and kettle times with efficiency.
  • I can compare designs against constraints and goals (mass, cost, output per dollar), and know the Carnot limit 1 − Tc ÷ Th.
  • I can judge claims (a 100%-efficient heater, a round-trip battery rating, ten points at 40% against ten points at 80%) and design a test that finds where energy is lost.

Standard: HS-PS3-3

Words to know

efficiency: Useful energy out ÷ energy in, as a percent

useful output: The energy in the form the device is for

energy balance: Energy in = useful out + wasted out

criterion / constraint: A goal to do well on / a limit not to break

percentage point: One percent of the whole, as in 40% to 50% = 10 points

Common mistakes

Your child left out g when finding the useful power. Lifting a mass needs m g h, with g = 9.8 m/s².

Your child divided the input by the useful output. Efficiency is useful out over in, so it stays below 100%.

Your child used only the first efficiency. Every stage in a chain loses some energy.

Questions parents ask

What is the most common mistake with compare devices that change energy from one form to another?

Your child left out g when finding the useful power. Lifting a mass needs m g h, with g = 9.8 m/s².

Are these 11th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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