Energy is never made and never destroyed — it just moves and changes form. In this mini-lesson you'll meet every form CCEA expects, the equations for kinetic and potential energy, work, power and efficiency, and how we generate electricity from renewable and non-renewable resources.
The Principle of Conservation of Energy: the total never changes.
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1.4.1 · Forms of energy
The many forms of energy
CCEA expects you to recall that energy exists in many forms:
Chemical — stored in fuel, food and batteries, released by reactions (combustion, respiration).
Heat (thermal) — the more particles vibrate, the more heat energy.
Electrical — energy carried when a current flows through a conductor.
Sound — needs vibrations travelling through a solid, liquid or gas (never a vacuum).
Light — emitted by luminous objects such as the Sun, stars and bulbs.
Magnetic — stored in a magnetic field around a magnet or electromagnet.
Strain (elastic) — stored in a stretched or compressed springy object.
Kinetic — the energy of any moving object.
Gravitational potential — stored because of an object's height above the ground.
Joules. Energy is measured in joules (J). 1 J is roughly the energy needed to lift an apple vertically 1 metre.
Quick check
Which form is stored?
?A diver stands on a high board, perfectly still, before jumping. Which form of energy is stored because of her position?
1.4.2–1.4.4 · Conservation & transfer diagrams
Energy is conserved
The Principle of Conservation of Energy states: energy can be changed from one form to another, but the total amount of energy does not change.
An energy transfer diagram shows the form energy starts in and the forms it transfers to. The arrow means "transfers to".
A torch: chemical → electrical → light (useful) + heat (wasted).
Watch out. Energy is never "used up" or destroyed. When we say energy is wasted, it has simply dissipated — usually as heat — and is no longer useful, but it still exists.
Trace the transfer
What does each device transfer to?
For each everyday device, choose the main output the energy transfers into.
1.4.11–1.4.12 · Efficiency
Efficiency: how much is useful?
Not all the energy supplied to a device is useful. Efficiency measures how much of the input energy appears as useful output energy.
efficiency = useful output energy ÷ total input energy
Quote it as a decimal, or × 100 for a percentage. Efficiency has no unit — it's a ratio, and is always less than 1 (or less than 100%).
A Sankey diagram. Width = amount of energy; useful output ÷ total input = efficiency.
Misconception buster. Efficiency can never be more than 1 (100%). If you ever calculate over 100%, you've divided the wrong way — useful goes on top.
Calculate · efficiency
Find the efficiency
=An electric drill is supplied with 500 J of electrical energy and produces 300 J of useful kinetic energy. Calculate its efficiency as a percentage.
%
Hint: efficiency = useful ÷ total = 300 ÷ 500, then × 100.
1.4.13–1.4.14 · Work done
Work done
Work is done whenever a force moves an object through a distance — energy is transferred from one form to another.
work = force × distance (W = F × d)
Work in joules (J) · Force in newtons (N) · distance in metres (m). Work done equals the energy transferred.
Worked example
A trolley is pushed with a force of 40 N for a distance of 3 m.
W = F × d = 40 × 3 = 120 J
No movement, no work. Holding a heavy bag still feels tiring, but if it doesn't move d = 0, so no work is done on the bag.
Calculate · work
How much work?
=A removal worker pushes a crate with a steady force of 250 N across a warehouse floor, moving it 6 m. How much work is done?
J
Hint: W = F × d = 250 × 6.
1.4.15–1.4.16 · Power
Power: energy per second
Power is the amount of energy transferred — or work done — every second. A powerful device transfers a lot of energy in a short time.
power = energy transferred ÷ time (P = E ÷ t)
Same as P = work done ÷ time. Power in watts (W), energy/work in joules (J), time in seconds (s). 1 W = 1 J/s.
Worked example
A motor transfers 900 J of energy in 15 s.
P = E ÷ t = 900 ÷ 15 = 60 W
Misconception buster. Power is a rate, not a total. Two pupils may do the same work climbing the stairs, but the one who does it faster is the more powerful — they used less time for the same energy.
Calculate · power
Work out the power
=A pupil doing the CCEA personal-power experiment runs up a staircase, doing 2400 J of work in 8 s. Calculate their power.
W
Hint: P = work ÷ time = 2400 ÷ 8.
1.4.19 · Kinetic energy
Kinetic energy EK
Kinetic energy is the energy possessed by a moving object. It depends on the object's mass and on the square of its speed.
EK = ½ m v²
EK in joules (J) · mass m in kilograms (kg) · speed v in metres per second (m/s).
Worked example
A cyclist of mass 80 kg moves at 5 m/s.
EK = ½ × 80 × 5² = ½ × 80 × 25 = 1000 J
Double the speed, quadruple the energy. Because v is squared, doubling the speed makes the kinetic energy 4 times bigger — a key reason fast crashes are so dangerous.
Calculate · kinetic energy
Find the kinetic energy
=A football of mass 0.4 kg is kicked so it travels at 20 m/s. Calculate its kinetic energy.
J
Hint: EK = ½ × 0.4 × 20². Remember to square the speed first.
1.4.20–1.4.21 · Gravitational potential energy
Gravitational potential energy EP
An object has gravitational potential energy because of its height above the ground.
EP = m g h
EP in joules (J) · mass m in kg · height h in m · g = 10 N/kg (CCEA value).
Worked example
A 2 kg book is lifted onto a shelf 1.5 m high.
EP = m g h = 2 × 10 × 1.5 = 30 J
Use g = 10 N/kg. CCEA takes Earth's gravitational field strength as 10 N/kg, so the weight of a 1 kg mass is 10 N. Always lift the mass against gravity — it's the vertical height that counts.
Calculate · potential energy
Find the potential energy
=A rock climber of mass 70 kg climbs a cliff to a vertical height of 12 m. Calculate the gravitational potential energy she has gained.
J
Hint: EP = m g h = 70 × 10 × 12.
Linking EP and EK
Falling: potential becomes kinetic
When an object falls, its gravitational potential energy is converted into kinetic energy as it accelerates towards the ground. Assuming no losses, the total energy is conserved from start to finish.
As the ball falls, EP drops and EK rises — but the total stays 100 J.
The clever shortcut. If no energy is lost, the kinetic energy at the bottom equals the potential energy at the top: ½ m v² = m g h. This lets you find the speed of a falling object.
Calculate · EP → EK
From height to speed
=A coconut of mass 2 kg falls from a palm tree 5 m high. Assuming no energy is lost, it arrives at the ground with kinetic energy equal to its potential energy at the top. What is its speed as it lands?
m/s
Hint: EP = mgh = 2 × 10 × 5 = 100 J. Then ½ m v² = 100, so v² = 100, v = √100.
1.4.5–1.4.7 · Renewable resources
Renewable energy resources
Renewable energy comes from resources that will never run out, or are naturally replenished within a human lifetime. CCEA's examples are:
Sunlight (solar) — solar cells convert sunlight straight into electricity.
Wind — moving air turns blades that drive a generator.
Hydroelectricity — water stored behind a dam falls and turns a turbine.
Tidal — a barrage across an estuary uses the rise and fall of the tide.
Waves — the up-and-down motion of waves drives a generator.
Wood (biomass) — burned in power stations; replanting makes it carbon neutral.
Geothermal heat — heat from hot rocks deep underground makes steam.
Environmental effects. Renewables aren't perfect — wind farms can cause visual pollution and harm low-flying birds, and tidal barrages can destroy aquatic habitats.
1.4.8–1.4.10 · Non-renewable resources
Non-renewable energy resources
A non-renewable resource has a finite supply and will eventually run out. CCEA expects:
Fossil fuels — coal, oil and natural gas — formed over millions of years; they cannot be replaced within a human lifetime.
Nuclear — based on fission of uranium; non-renewable because uranium ore supplies will not last forever.
Renewables are replenished; non-renewables are finite.
Environmental effects. Burning fossil fuels releases CO₂ causing global warming, and sulfur dioxide causing acid rain. Nuclear makes no CO₂ but produces dangerous radioactive waste.
Sort it · resources
Renewable or non-renewable?
Tap a resource, then tap the box it belongs in.
♻️ Renewable
⛽ Non-renewable
Quick check
Spotting a mistake
?A pupil calculates that a lamp is "120% efficient". What does this tell you?
Quick check
Where did the energy go?
?A bouncing ball ends up at rest on the ground. A pupil says "all its energy was used up and destroyed". What is the correct explanation?
Quick check
Who is more powerful?
?Cara and Dev each transfer 200 J of energy lifting a load up a flight of stairs. Cara takes 4 s; Dev takes 8 s. Who is more powerful, and why?
Recap
The equations to know
Kinetic energy: EK = ½ m v²
Gravitational potential energy: EP = m g h (g = 10 N/kg)
Work done: W = F × d (= energy transferred)
Power: P = E ÷ t = work ÷ time
Efficiency: useful output ÷ total input (× 100% for a percentage, no unit)
Conservation: energy changes form but the total never changes
You've covered the whole of CCEA Unit 1.4 — Energy: forms of energy, conservation and transfer diagrams, efficiency, work, power, kinetic and potential energy, and energy resources. Press Finish to see your score.
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