9478 / 2027

Chapter 4

Energy and Fields

Choose a system and identify its energy changes before deciding which force, displacement or time interval to use.

Use energy accounts and field models to explain transfers and calculate useful output.

Energy stores and transfers, work and kinetic energy, gravitational and electric fields, equipotential surfaces, potential energy, power and efficiency. For 9478 (2027).

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Choose a topic

  1. Account for energy stores and transfers

    Choose a system boundary and use conservation without counting a transfer and its resulting store increase twice.

  2. Work and kinetic energy

    Use force and displacement directions, derive kinetic energy and distinguish pulling work from net work.

  3. Field strength, patterns and force

    Define gravitational and electric field strength and interpret uniform and radial field lines.

  4. Field work and potential energy

    Relate field force and displacement to gravitational or electric potential-energy changes, including either charge sign.

  5. Elastic energy from a force-extension graph

    Calculate stored elastic energy from graph area and state when loading work is recoverable.

  6. Power, losses and efficiency

    Distinguish energy from power, use the force component along motion and compare useful output with total input.