Energy, work & power · revision map · IGCSE 0625, Topic 1.7

TOPIC 1.7 · ENERGY, WORK & POWER
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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ENERGY1.7
Energy Stores & Conservation

Energy is stored and transferred, never made or destroyed. In any change the total energy stays the same.

  • Stores: kinetic, gravitational, elastic, chemical, thermal, nuclear, electrostatic.
  • Transfers: by forces (work), heating, waves, electric current.
  • Energy often spreads out and becomes less useful (dissipated).
Kinetic Energy

Energy of a moving object. Doubling speed gives four times the kinetic energy.

Ek = ½ m v²
m = mass (kg), v = speed (m/s) · unit joule (J)
v
Gravitational PE

Energy stored when a mass is lifted in a gravitational field.

ΔEp = m g Δh
g = gravitational field strength · Δh = change in height
high: more GPE falls: GPE to KE
Work Done

Work is the energy transferred by a force moving its point of application.

W = F d
F = force (N), d = distance moved in the direction of F
  • 1 joule = work done when 1 N moves through 1 m.
  • Work done = energy transferred (in joules).
Power

How fast energy is transferred (rate of energy transfer or rate of doing work).

P = ΔE / t P = W / t
ΔE = energy, W = work, t = time
unit watt (W); 1 W = 1 J/s
Efficiency

Compares the useful output with the total energy put in.

efficiency = useful ÷ total input useful output wasted heat
Energy Resources

Electricity comes from generators driven by a range of resources.

Non-renewable
fossil fuels (coal, oil, gas), nuclear
Renewable
solar, wind, hydro, tidal, geothermal, biofuel
  • The Sun is the source of most of these resources.
BUILDS ON · Mass & weight · Forces → ENERGY → LEADS TO · Thermal energy
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