Energy, Work and Power

2026 Syllabus Objectives

By the end of this topic, you should be able to:

1.7.1 Energy

  • Core:
    • State that energy may be stored as kinetic, gravitational potential, chemical, elastic (strain), nuclear, electrostatic and internal (thermal)
    • Describe how energy is transferred between stores during events and processes
    • Know and apply the principle of conservation of energy to simple examples
  • Supplement:
    • Recall and use the equation for kinetic energy: Ek = ½mv²
    • Recall and use the equation for change in gravitational potential energy: ΔEp = mgΔh
    • Apply conservation of energy to complex examples including Sankey diagrams

1.7.2 Work

  • Core:
    • Understand that mechanical or electrical work done equals energy transferred
    • Recall and use the equation: W = Fd = ΔE

1.7.3 Energy Resources

  • Core:
    • Describe how useful energy is obtained from various sources (fossil fuels, biofuels, water, geothermal, nuclear, solar)
    • Describe advantages and disadvantages of each method
    • Understand the concept of efficiency qualitatively
  • Supplement:
    • Know that the Sun is the main source of energy for most resources
    • Know that nuclear fusion releases energy in the Sun
    • Know about nuclear fusion research for large-scale electrical energy
    • Define and calculate efficiency using formulas

1.7.4 Power

  • Core:
    • Define power as work done per unit time and energy transferred per unit time
    • Recall and use: P = W/t and P = ΔE/t

Main Content

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What is Energy?

Energy is the ability to do work. It is what makes things happen - it allows objects to move, heat up, light up, or make sounds. Energy is a scalar quantity, which means it has size (magnitude) but no direction. We measure energy in joules (J).

Energy cannot be created or destroyed - it can only be converted (changed) from one form to another or transferred (moved) from one object to another. This is called the principle of conservation of energy.

Energy Stores

Energy can be stored in different ways. These different ways are called energy stores. There are eight main types:

  1. Kinetic energy - energy stored in moving objects. A rolling ball, a flying bird, and a moving car all have kinetic energy.

  2. Gravitational potential energy - energy stored in objects that have been lifted up in a gravitational field. A book on a high shelf has more gravitational potential energy than one on a low shelf.

  3. Chemical energy - energy stored in substances that can release it through chemical reactions. Food, batteries, and fuels (like petrol or coal) store chemical energy.

  4. Elastic (strain) energy - energy stored in objects that have been stretched, squashed, or bent. A stretched rubber band, a compressed spring, and a bent ruler all have elastic energy.

  5. Nuclear energy - energy stored in the nucleus (central part) of atoms. This energy is released during nuclear reactions like fission (splitting atoms) or fusion (joining atoms).

  6. Electrostatic energy - energy stored when charged particles (like electrons and protons) interact with each other. For example, when you rub a balloon on your hair, it gains electrostatic energy.

  7. Magnetic energy - energy stored when magnetic materials interact. Two magnets pushing or pulling each other have magnetic energy.

  8. Internal (thermal) energy - energy stored in the random movement of particles in a substance. All objects have internal energy - the hotter an object is, the more internal energy it has.

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