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Energy transfers

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Question 13

The following typical household electrical appliances are used in a home:

  • A electric toaster
  • B desk fan
  • C LED spotlight
  • D doorbell
a.

(i) Which appliance is designed to transfer electrical energy primarily to kinetic energy? (ii) Which appliance is designed to transfer electrical energy primarily to thermal energy?

[2]
b.

In all these appliances, energy is conserved. Explain what is meant by the law of conservation of energy.

[2]
c.

(i) The LED spotlight has an efficiency of 35%. Explain what this means. (ii) If the LED spotlight has a total input energy of 400 J:

  1. Calculate the useful energy output.
  2. Calculate the wasted energy output.
  3. Describe how these energy transfers are represented on a labelled Sankey diagram (including arrow widths and directions).
[6]

Energy transfers Questions

  1. IGCSE
  2. /Physics
  3. /Energy transfers