GCSE Combined Science (AQA)

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Principle of Conservation of Energy

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Energy Conservation and dissipation of energy

Principle of Conservation of Energy

4:52 Conservation of Energy
Spec 4.1.2.1 4.1.1.1
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  • Conservation of energy principle: energy cannot be created or destroyed, only stored, transferred, or converted.
  • Example: energy transfer between a battery and a bulb involves chemical energy converting to electrical current, then to light and heat.
  • Closed system: total energy remains the same after any energy transfer; no energy is added or removed.
  • Open system: can exchange energy with surroundings; most systems are open.
  • Kettle example: electrical energy converts to thermal energy in water, illustrating a closed system.
  • Throwing an apple: kinetic energy converts to gravitational potential energy as it rises, and vice versa as it falls.
  • Some energy converts to heat due to air resistance, warming the apple and surrounding air.
  • Mathematical representation: in a closed system, total energy before and after a transfer is equal.
  • Plane example: 120 megajoules of chemical energy converts to 30 megajoules of kinetic energy and 90 megajoules of gravitational potential energy.
  • Exam expectation: describe energy changes in simple systems like a kettle or projectile.
  • Shopping trolley example: Farah and Liam provide 250 joules of energy, resulting in 80 joules of gravitational potential energy and 170 joules of kinetic energy.
  • Calculation steps: total energy before transfer, total energy after transfer, and calculating kinetic energy gained.

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