Energy is a core part of GCSE Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Energy storesKinetic, gravitational, elastic, thermal, chemical, etc.
Energy transfersEnergy moved between stores mechanically, electrically, by heating or radiation.
Conservation of energyEnergy cannot be created or destroyed, only transferred.
EfficiencyUseful energy out ÷ total energy in (always less than 100%).
Work doneEnergy transferred when a force moves an object; W = Fd.
PowerThe rate of energy transfer (watts); P = E ÷ t.
Energy storee.g. kinetic, gravitational, chemical
Energy transferMechanical, electrical, heating, radiation
ConservationEnergy cannot be created or destroyed
DissipationWasted to surroundings
KE = 1/2 mv^2Kinetic energy formula
KE = 1/2 m v^2Kinetic energy
GPE = m g hGravitational PE
g9.8 N/kg on Earth (or 10)
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
If a car doubles its speed, what happens to its kinetic energy?✗ Kinetic energy doubles because energy is proportional to speed. ✓ It quadruples (because KE = 1/2 mv^2 — kinetic energy is proportional to v^2).
When energy is 'lost' as heat due to friction, what has really happened?✗ Energy has been used up and no longer exists. ✓ Energy has been transferred to the thermal store of the surroundings — it's not destroyed, just dissipated.
Can a device ever be 100 percent efficient?✗ A well-designed device can be 100 percent efficient by eliminating all friction. ✓ In practice, no — some energy is always transferred to less useful stores (e.g. heat to surroundings).
What is the difference between energy and power?✗ Energy and power are the same — both describe how much fuel something uses. ✓ Energy is measured in joules; power is the rate of energy transfer, measured in watts (joules per second).
Which is the best way to reduce energy wasted as heat in a moving machine?✗ Painting it black ✓ Adding lubrication
Practise Energy — free games
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