Energy flashcards

Energy is a fundamental concept in GCSE Physics. Students must understand the different stores of energy (kinetic, gravitational potential, elastic potential, thermal, chemical, nuclear, electrostatic and magnetic) and the ways energy is transferred between them (mechanically, electrically, by heating and by radiation). The principle of conservation of energy states that energy cannot be created or destroyed, only transferred between stores or dissipated to the surroundings. Students must be able to calculate kinetic energy, gravitational potential energy and work done, and understand the concept of efficiency. Power is the rate of energy transfer, measured in watts. Energy resources, both renewable and non-renewable, and their environmental impacts are also essential. Understanding how to reduce unwanted energy dissipation, for example through insulation, is important for real-world applications.

1. Card 1

   What is the principle of conservation of energy?

   Energy cannot be created or destroyed. It can only be transferred between stores or dissipated to the surroundings.

2. Card 2

   State the formula for kinetic energy.

   Kinetic energy (KE) = 0.5 x mass x velocity squared, or KE = 0.5 x m x v^2. The unit is the joule (J).

3. Card 3

   State the formula for gravitational potential energy.

   Gravitational potential energy (GPE) = mass x gravitational field strength x height, or GPE = m x g x h. Units are joules (J).

4. Card 4

   What is meant by work done in physics?

   Work done is the energy transferred when a force moves an object through a distance. Work done = force x distance (W = F x d), measured in joules.

5. Card 5

   How is efficiency calculated?

   Efficiency = useful output energy transfer divided by total input energy transfer. It can be expressed as a decimal or percentage. A perfectly efficient device has an efficiency of 1 (or 100%).

6. Card 6

   What is power and what is its unit?

   Power is the rate at which energy is transferred or work is done. It is calculated as energy transferred divided by time. The unit is the watt (W).

7. Card 7

   Name four stores of energy.

   Four stores are kinetic, gravitational potential, elastic potential and thermal. Others include chemical, nuclear, electrostatic and magnetic stores.

8. Card 8

   What is meant by dissipation of energy?

   Dissipation means energy is spread out into the surroundings, usually as thermal energy. This energy is no longer useful and cannot easily be recovered.

9. Card 9

   Give two ways of reducing unwanted energy transfers in a system.

   Lubrication reduces friction between moving parts, and insulation reduces thermal energy transfer through walls or pipes, improving efficiency.

10. Card 10

    What is the difference between renewable and non-renewable energy resources?

    Non-renewable resources (e.g. fossil fuels) will eventually run out. Renewable resources (e.g. wind, solar) are replenished naturally and will not run out.

11. Card 11

    A ball of mass 2 kg moves at 3 m/s. What is its kinetic energy?

    KE = 0.5 x 2 x 3^2 = 0.5 x 2 x 9 = 9 joules. Remember to square the velocity before multiplying.

12. Card 12

    What energy store changes when a spring is compressed?

    Compressing a spring increases the elastic potential energy stored in it. This can be released and transferred to kinetic energy when the spring is let go.

• Many students confuse energy stores with energy transfers, for example describing electricity as a store rather than a way of transferring energy.
• A very common exam error is forgetting to square the velocity when calculating kinetic energy using KE = 0.5 x m x v^2, leading to answers that are far too small.
• Students often state that energy is lost or destroyed in an inefficient process, when in fact energy is always conserved but some is dissipated as thermal energy to the surroundings.

Planning your revision? Read how to revise GCSE Physics, or make cards from your own notes with the notes to flashcards tool.