An object is in motion when its position changes over time, compared to a reference point. Speed tells us how quickly that change happens.
📍 What is motion?
Motion is a change in position relative to a reference point — something we assume is standing still, like a tree or a building.
Distance is the total path length traveled. Displacement is how far an object ends up from where it started, in a straight line.
🏃 Calculating speed
speed = distance ÷ time
A car travels 150 km in 3 hours.
speed = 150 ÷ 3 = 50 km/h
Speed is usually measured in metres per second (m/s) or kilometres per hour (km/h).
📈 Reading a distance-time graph
On a distance-time graph, a steeper line means a faster speed — more distance is covered in the same amount of time.
steeper line = faster speed
📝 Worked examples
speed = distance ÷ time
120 m in 20 s → 6 m/s
90 km in 1.5 h → 60 km/h
acceleration = (final speed − start speed) ÷ time
0 → 20 m/s in 5 s → 4 m/s²
On a distance–time graph the slope is the speed: a steeper line is faster and a flat line means the object is stopped.
Speed has only size. Velocity has size and direction: 10 m/s north.
✏️ Quick check · 1 of 10
Identify the speed formula
Which formula correctly calculates speed?
Think of the unit km per hour: distance per time.
✍️ Type your answer · 2 of 10
A cyclist travels 200 km in 4 hours.
What is the cyclist's speed, in km/h?
Enter an exact answer, without rounding.
km/h
Speed = distance ÷ time: 200 ÷ 4.
✏️ Quick check · 3 of 10
Units of speed
Which of these is a correct unit for speed?
Speed is a distance divided by a time.
✍️ Type your answer · 4 of 10
A train covers 120 km at a speed of 40 km/h.
How many hours did the trip take?
Enter an exact answer, without rounding.
hours
Time = distance ÷ speed: 120 ÷ 40.
✏️ Quick check · 5 of 10
Read the graph
On a distance-time graph, a steeper line means:
A steeper line covers more distance in the same time.
✍️ Type your answer · 6 of 10
A bus travels at 60 km/h for 2.5 hours.
How far does it travel, in km?
Enter an exact answer, without rounding.
km
Distance = speed × time: 60 × 2.5.
✏️ Quick check · 7 of 10
Flat line
On a distance–time graph, a horizontal line means the object is:
What happens to distance as time passes?
✏️ Quick check · 8 of 10
Velocity
What does velocity include that speed does not?
Think "10 m/s north".
✍️ Type your answer · 9 of 10
A runner travels at 5 m/s for 12 s.
How far does she go?
Enter an exact answer, without rounding.
m
Multiply speed by time.
✍️ Type your answer · 10 of 10
A car speeds up from 2 m/s to 14 m/s in 4 s.
What is its acceleration?
Enter an exact answer, without rounding.
m/s²
Find the change in speed, then divide by the time.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
How long does it take to travel 100 m at 5 m/s?
Question 2 of 5
Which unit is used for speed?
Question 3 of 5
Which has the greater speed on a distance–time graph?
Question 4 of 5
A car travels 150 km in 2 h. What is its average speed?
Question 5 of 5
A cyclist speeds up from 10 m/s to 30 m/s in 4 s. What is the acceleration?
Lesson 2 · Forces
💪 Forces & Newton's Laws
A force is a push or a pull. Isaac Newton described exactly how forces control the motion of everything around us in three simple laws.
⚖️ Balanced vs. unbalanced forces
When forces on an object are balanced, they cancel out and the object's motion doesn't change. When they're unbalanced, there's a leftover net force that causes the object to accelerate.
Balanced forces
Unbalanced forces
🔬 Newton's three laws
1st Law: Inertia
An object at rest stays at rest, and an object in motion stays in motion, unless acted on by a force.
2nd Law: F = ma
Force equals mass times acceleration.
3rd Law: For every action, there is an equal and opposite reaction. When you push on a wall, it pushes back on you just as hard.
🧮 Using F = ma
Force = mass × acceleration
mass = 5 kg, acceleration = 2 m/s²
Force = 5 × 2 = 10 N
📝 Worked examples
F = m × a
10 N on a 2 kg object → a = 10 ÷ 2 = 5 m/s²
Net force: 15 N right and 5 N left → 10 N right
Balanced forces (net force = 0) → no change in motion
Action and reaction forces act on different objects, so they never cancel each other out.
✏️ Quick check · 1 of 10
Balanced forces and motion
When the forces on an object are balanced, the object:
Balanced forces cause no change in motion.
✍️ Type your answer · 2 of 10
An object has a mass of 5 kg and accelerates at 2 m/s².
What force is acting on it, in newtons?
Enter an exact answer, without rounding.
N
F = m × a: 5 × 2.
✏️ Quick check · 3 of 10
Newton's third law
Which statement describes Newton's third law?
Push on a wall and the wall pushes back on you.
✍️ Type your answer · 4 of 10
A 4 kg object experiences a force of 20 N.
What is its acceleration, in m/s²?
Enter an exact answer, without rounding.
m/s²
a = F ÷ m: 20 ÷ 4.
✏️ Quick check · 5 of 10
Newton's first law
Newton's first law is also known as the law of:
Objects resist changes to how they are moving.
✍️ Type your answer · 6 of 10
A 10 kg object accelerates at 3 m/s².
What force is acting on it, in newtons?
Enter an exact answer, without rounding.
N
F = m × a: 10 × 3.
✏️ Quick check · 7 of 10
Balanced forces
An object has balanced forces acting on it. It will:
Net force of zero.
✏️ Quick check · 8 of 10
Seat belts
A seat belt is needed mostly because of:
The passenger wants to keep moving.
✍️ Type your answer · 9 of 10
A 6 kg object accelerates at 3 m/s².
What net force acts on it?
Enter an exact answer, without rounding.
N
Multiply mass by acceleration.
✍️ Type your answer · 10 of 10
Forces on a box: 30 N to the right and 12 N to the left.
What is the net force to the right?
Enter an exact answer, without rounding.
N
Subtract the opposite forces.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
Newton's first law says an object keeps its motion unless:
Question 2 of 5
A 20 N net force acts on a 4 kg object. What is its acceleration?
Question 3 of 5
Which pair is an action–reaction pair?
Question 4 of 5
A rocket pushes gas down. The gas pushes the rocket up. This is Newton's:
Question 5 of 5
An unbalanced force on an object causes:
Lesson 3 · Forces
🛑 Types of Forces: Friction, Contact & Non-Contact
Not all forces work the same way — some need objects to touch, others act from a distance, and friction is one of the most common forces you feel every day.
✋️ Contact vs. non-contact forces
Forces are either contact forces, which require the objects to be touching — like friction, normal force, and tension — or non-contact forces, which act at a distance without touching — like gravity, magnetism, and electrostatic force.
Friction is a contact force that opposes motion between two touching surfaces. Rougher surfaces create more friction, and friction can be reduced (lubricants, wheels, smoother surfaces) or increased (rough treads) depending on what's needed.
Normal force is the support force a surface pushes back with, perpendicular to itself, balancing an object's weight. Tension is the pulling force transmitted through a stretched rope, string, or cable.
applied forcefrictionweightnormal force
📝 Worked examples
A book resting on a table:
Gravity pulls it DOWN (weight).
The table pushes it UP (normal force).
The forces are equal and opposite → net force 0.
Push 40 N, friction 15 N opposing → net force = 40 − 15 = 25 N
Which of these is a contact force (requires touching)?
Which one only acts when two surfaces rub together?
✏️ Quick check · 2 of 9
Spot the non-contact force
Which of these is a non-contact force (acts at a distance)?
Which one pulls even when nothing is touching?
✏️ Quick check · 3 of 9
Define normal force
The force that pushes back against an object's weight, perpendicular to the surface it rests on, is called:
It is the push from the surface, at 90° to it.
✍️ Type your answer · 4 of 9
A block has a weight of 20 N pressing straight down on a table, and the block stays still (forces are balanced).
For the block to stay balanced, what must the normal force be, in N?
Enter an exact answer, without rounding.
N
Balanced means the upward push equals the downward weight.
✍️ Type your answer · 5 of 9
Every force introduced in this lesson falls into one of two broad categories.
How many main categories do all forces fall into (contact and non-contact)?
Enter an exact answer, without rounding.
Contact and non-contact.
✏️ Quick check · 6 of 9
Opposing motion
Which force opposes the sliding of one surface over another?
Rough surfaces create more of it.
✏️ Quick check · 7 of 9
Normal force
The normal force from a table on a book points:
It supports the book.
✍️ Type your answer · 8 of 9
A 50 N box rests on a flat table, not moving.
What is the normal force on it?
Enter an exact answer, without rounding.
N
Net force is zero.
✍️ Type your answer · 9 of 9
You push a crate with 40 N. Friction is 15 N.
What is the net force?
Enter an exact answer, without rounding.
N
Subtract friction from the push.
📝 Lesson quiz · 5 questions
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Re-read the lesson, then give it another go.
Question 1 of 5
The pulling force in a stretched rope is called:
Question 2 of 5
Air resistance on a falling object:
Question 3 of 5
Oil on a bike chain helps because it:
Question 4 of 5
Which is a non-contact force?
Question 5 of 5
A skydiver reaches terminal velocity when:
Lesson 4 · Forces
⚖️ Pressure
Pressure is force spread over an area. The same force can feel very different depending on how much area it's spread across — that's why a sharp knife cuts easily, but a flat hand doesn't.
📊 Calculating pressure
Pressure tells us how concentrated a force is. It's calculated by dividing the force by the area it acts on.
Pressure = force ÷ area
force = 50 N, area = 2 m²
Pressure = 50 ÷ 2 = 25 Pa
Pressure is measured in pascals (Pa), where 1 Pa equals 1 newton per square meter (1 Pa = 1 N/m²).
If the same force is spread over a smaller area, the pressure goes up — that's why a knife's thin edge cuts through food so easily. Spread that same force over a larger area, like a snowshoe, and the pressure goes down, which stops you from sinking into soft snow.
Small area (high pressure)
Large area (low pressure)
📝 Worked examples
pressure = force ÷ area
200 N on 0.5 m² → P = 400 Pa
force = pressure × area
50 Pa on 4 m² → F = 200 N
Liquid pressure rises with depth. Atmospheric pressure is about 100 000 Pa at sea level and falls as you climb.
Same force, smaller area, bigger pressure: that is why needles are sharp and snowshoes are wide.
✏️ Quick check · 1 of 10
Identify the pressure formula
Which formula correctly calculates pressure?
Pressure is force spread over an area.
✏️ Quick check · 2 of 10
Force over a smaller area
If the same force is applied over a smaller area, the pressure:
Think of a sharp knife compared with a blunt one.
✏️ Quick check · 3 of 10
Units of pressure
What is the standard unit of pressure?
It is named after the scientist Blaise Pascal.
✍️ Type your answer · 4 of 10
A force of 50 N is applied over an area of 2 m².
What is the pressure, in Pa?
Enter an exact answer, without rounding.
Pa
Pressure = force ÷ area: 50 ÷ 2.
✍️ Type your answer · 5 of 10
A force of 100 N is applied over an area of 4 m².
What is the pressure, in Pa?
Enter an exact answer, without rounding.
Pa
Pressure = force ÷ area: 100 ÷ 4.
✍️ Type your answer · 6 of 10
A force of 20 N is applied over an area of 5 m².
What is the pressure, in Pa?
Enter an exact answer, without rounding.
Pa
Pressure = force ÷ area: 20 ÷ 5.
✏️ Quick check · 7 of 10
Pressure formula
Pressure is calculated as:
Force per unit area.
✏️ Quick check · 8 of 10
Wide tyres
Why do tractors have wide tyres?
More area, less pressure.
✍️ Type your answer · 9 of 10
A 600 N force acts on 3 m².
What is the pressure?
Enter an exact answer, without rounding.
Pa
Divide the force by the area.
✍️ Type your answer · 10 of 10
A pressure of 50 Pa acts on 4 m².
What is the force?
Enter an exact answer, without rounding.
N
Multiply pressure by area.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
The SI unit of pressure is:
Question 2 of 5
If the contact area is halved and the force stays the same, pressure:
Question 3 of 5
As you dive deeper in water, the pressure:
Question 4 of 5
90 N acts on 0.3 m². What is the pressure?
Question 5 of 5
Atmospheric pressure at the top of a mountain, compared with sea level, is:
Lesson 5 · Forces
🌍 Gravity & Weight
Gravity is the force that pulls objects toward each other. On Earth, it's what keeps your feet on the ground and gives everything its weight.
⚖️ Mass vs. weight
Mass is the amount of matter in an object — it never changes, no matter where you are. Weight is the force of gravity pulling on that mass, and it changes depending on the gravity around you.
Mass
Measured in kilograms (kg). Stays the same on Earth, the Moon, or in space.
Weight
Measured in newtons (N). Changes with the strength of gravity.
🧮 Calculating weight
Weight = mass × gravity
On Earth, gravity pulls with an acceleration of about g = 10 m/s² (a rounded value used for easy calculations).
mass = 5 kg
Weight = 5 × 10 = 50 N
🌙 Gravity on other worlds
The Moon's gravity is about 1/6th as strong as Earth's. That means an object with the same mass weighs much less on the Moon — even though its mass hasn't changed at all.
🖼️ See it
The mass stays 10 kg everywhere; weight = mass × gravitational field strength, so it changes from world to world (Earth 10, Moon 1.6, Mars 3.7, Jupiter 25 N/kg).
📝 Worked examples
weight = mass × g (g = 10 N/kg on Earth)
5 kg → W = 5 × 10 = 50 N
On the Moon g ≈ 1.6 N/kg
5 kg → W = 5 × 1.6 = 8 N
Mass stays 5 kg everywhere.
Mass is how much matter there is (kg). Weight is the pull of gravity on it (N). Mass never changes; weight does.
✏️ Quick check · 1 of 10
Mass vs. weight
Which quantity stays the same no matter where you are in the universe?
One depends on gravity; the other is the amount of matter.
✍️ Type your answer · 2 of 10
Use g = 10 m/s².
What is the weight of a 5 kg object, in newtons?
Enter an exact answer, without rounding.
N
Weight = mass × g: 5 × 10.
✏️ Quick check · 3 of 10
Earth's gravity
Which value is commonly used for gravity's acceleration on Earth, for easy calculations?
It is close to 9.8 and rounds to a simple number.
✍️ Type your answer · 4 of 10
Use g = 10 m/s².
What is the weight of an 8 kg object, in newtons?
Enter an exact answer, without rounding.
N
Weight = mass × g: 8 × 10.
✏️ Quick check · 5 of 10
Weight on the Moon
If you brought an object to the Moon, its weight would:
The Moon’s gravity is weaker than Earth’s.
✍️ Type your answer · 6 of 10
Use g = 10 m/s².
What is the weight of a 20 kg object, in newtons?
Enter an exact answer, without rounding.
N
Weight = mass × g: 20 × 10.
✏️ Quick check · 7 of 10
Units
Weight is measured in:
It is a force, so use the unit of force.
✏️ Quick check · 8 of 10
On the Moon
An astronaut goes to the Moon. Which changes?
Mass is amount of matter.
✍️ Type your answer · 9 of 10
Use g = 10 N/kg.
What is the weight of a 7 kg object?
Enter an exact answer, without rounding.
N
Multiply mass by 10.
✍️ Type your answer · 10 of 10
An object weighs 120 N on Earth (g = 10 N/kg).
What is its mass?
Enter an exact answer, without rounding.
kg
Divide the weight by g.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
What is the weight of a 40 kg student on Earth (g = 10)?
Question 2 of 5
Mass is:
Question 3 of 5
Gravity is stronger between objects that:
Question 4 of 5
A 10 kg object on the Moon (g = 1.6) weighs about:
Question 5 of 5
In deep space, far from any planet, a 5 kg object has:
Lesson 6 · Energy
⚡ Energy: Types & Forms
Energy is the ability to do work or cause change. It comes in many forms, and it's always moving from one form to another — never created or destroyed.
🏃 Kinetic energy
Kinetic energy is the energy of motion. The faster or heavier something is, the more kinetic energy it has.
KE = ½ × mass × velocity²
mass = 2 kg, velocity = 3 m/s
KE = ½ × 2 × 3² = ½ × 2 × 9 = 9 J
🌌 Potential energy
Potential energy is stored energy, based on an object's position or condition — like height above the ground.
PE = mass × gravity × height
mass = 5 kg, gravity = 10 m/s², height = 2 m
PE = 5 × 10 × 2 = 100 J
♻️ Conservation of energy
The law of conservation of energy says energy can't be created or destroyed — only changed from one form to another. A ball at the top of a hill has lots of potential energy; as it rolls down, that potential energy turns into kinetic energy.
💡 Forms of energy
Energy shows up in many different forms. Here are some of the most common ones:
Kinetic — the energy of motion.
Gravitational Potential — stored energy based on height above the ground.
Chemical — stored in food, fuel, and batteries, released through reactions.
Elastic Potential — stored in stretched or compressed springs and rubber bands.
Thermal — the energy of heat, from the motion of particles.
Light — energy that travels as electromagnetic waves we can see.
Sound — energy that travels as vibrations through a medium.
chemical energy inlight energy outwasted heat outA simplified example of how a flashlight converts one form of energy into others.
📝 Worked examples
Gravitational PE = m × g × h
2 kg at 3 m (g = 10) → 2 × 10 × 3 = 60 J
Kinetic energy = ½ × m × v²
2 kg at 4 m/s → ½ × 2 × 16 = 16 J
Energy changes form, but the total never changes. A solar panel turns light into electrical energy; a toaster turns electrical energy into heat.
Law of conservation of energy: energy cannot be created or destroyed, only transformed.
✍️ Type your answer · 1 of 10
An object has a mass of 2 kg and moves at 3 m/s.
What is its kinetic energy, in joules?
Enter an exact answer, without rounding.
J
KE = ½ × m × v²: square the speed first.
✏️ Quick check · 2 of 10
The potential energy formula
Which formula calculates gravitational potential energy?
It depends on how high something is.
✍️ Type your answer · 3 of 10
Use g = 10 m/s².
A 5 kg object sits 2 m above the ground. What is its potential energy, in joules?
Enter an exact answer, without rounding.
J
PE = m × g × h: 5 × 10 × 2.
✏️ Quick check · 4 of 10
Law of conservation of energy
The law of conservation of energy states that energy:
Energy only changes from one form to another.
✍️ Type your answer · 5 of 10
An object has a mass of 4 kg and moves at 5 m/s.
What is its kinetic energy, in joules?
Enter an exact answer, without rounding.
J
KE = ½ × 4 × 5².
✏️ Quick check · 6 of 10
Energy transformation
A ball rolling down a hill is converting which type of energy into kinetic energy?
At the top of the hill the ball has stored energy because of its height.
✏️ Quick check · 7 of 10
Stored in food
What type of energy is stored in food?
Think about what your body "burns".
✏️ Quick check · 8 of 10
Moving energy
The energy an object has because it is moving is:
Moving means kinetic.
✍️ Type your answer · 9 of 10
A 5 kg object is 2 m above the ground (g = 10).
What is its gravitational potential energy?
Enter an exact answer, without rounding.
J
PE = mgh.
✍️ Type your answer · 10 of 10
A 4 kg object moves at 3 m/s.
What is its kinetic energy?
Enter an exact answer, without rounding.
J
Square the speed first.
📝 Lesson quiz · 5 questions
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Re-read the lesson, then give it another go.
Question 1 of 5
What is the KE of a 1 kg ball moving at 2 m/s?
Question 2 of 5
A stretched spring stores:
Question 3 of 5
Energy can be:
Question 4 of 5
A solar panel changes:
Question 5 of 5
What is the PE of a 10 kg object raised 1 m (g = 10)?
Lesson 7 · Energy
⚙️ Work & Simple Machines
In physics, "work" has a precise meaning: applying a force that moves something. Simple machines don't reduce the work needed — they just make it easier to apply the force.
💪 Calculating work
Work = force × distance
force = 20 N, distance = 5 m
Work = 20 × 5 = 100 J
Work is measured in joules (J) — the same unit used for energy, since doing work transfers energy.
⚖️ The lever
A lever is a bar that pivots on a fulcrum. Pushing down on the long "effort arm" lifts a heavy load sitting on the short "load arm" — trading distance for force.
A longer effort arm needs less force to lift the same load.
📊 Mechanical advantage
Mechanical advantage = load ÷ effort
A bigger mechanical advantage means the machine multiplies your force more. Levers, pulleys, ramps, wedges, screws, and wheel-and-axles are all simple machines.
📝 Worked examples
work = force × distance
50 N × 4 m = 200 J
power = work ÷ time
200 J ÷ 10 s = 20 W
mechanical advantage = load ÷ effort
60 N ÷ 20 N = 3
Simple machines (lever, pulley, ramp, wheel and axle, wedge, screw) make a job easier by trading force for distance. They do not reduce the total work.
No movement, no work. If the distance is zero, the work is zero.
✍️ Type your answer · 1 of 10
A force of 20 N moves an object 5 m.
How much work is done, in joules?
Enter an exact answer, without rounding.
J
Work = force × distance: 20 × 5.
✏️ Quick check · 2 of 10
Spot the simple machine
Which of these is NOT a simple machine?
Which one stores energy instead of helping you move a load?
✍️ Type your answer · 3 of 10
A force of 15 N moves an object 4 m.
How much work is done, in joules?
Enter an exact answer, without rounding.
J
Work = force × distance: 15 × 4.
✏️ Quick check · 4 of 10
Define mechanical advantage
Mechanical advantage measures:
Load ÷ effort tells you how much easier the job is.
✍️ Type your answer · 5 of 10
A lever lifts a 100 N load using only 20 N of effort.
What is the mechanical advantage?
Enter an exact answer, without rounding.
Mechanical advantage = load ÷ effort: 100 ÷ 20.
✏️ Quick check · 6 of 10
What simple machines actually do
Simple machines make tasks easier mainly by:
You push with less force, but over a longer distance.
✏️ Quick check · 7 of 10
Unit of work
Work is measured in:
Work and energy share a unit.
✏️ Quick check · 8 of 10
Seesaw
A seesaw is an example of a:
It pivots around a point.
✍️ Type your answer · 9 of 10
A 30 N force moves an object 6 m.
How much work is done?
Enter an exact answer, without rounding.
J
Multiply force by distance.
✍️ Type your answer · 10 of 10
A machine does 500 J of work in 25 s.
What is its power?
Enter an exact answer, without rounding.
W
Divide work by time.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
Which of these is a simple machine?
Question 2 of 5
An inclined plane (ramp) lets you:
Question 3 of 5
You push a wall with 100 N but it does not move. The work done is:
Question 4 of 5
A machine has a load of 80 N and a mechanical advantage of 4. What effort is needed?
Question 5 of 5
Power is:
Lesson 8 · Thermal Energy
🌡️ Heat & Temperature
Temperature and heat sound similar, but they're different ideas. Heat always flows from hot to cold, using one of three methods.
🌡️ Temperature vs. heat
Temperature measures how hot or cold something is, on average. Heat is the energy that flows between objects because of a temperature difference.
Heat moves through direct contact, like a metal spoon heating up in hot soup.
Convection
Heat moves through the flow of a liquid or gas, like warm air rising in a room.
Radiation: Heat travels as waves, needing no matter at all — this is how the Sun's warmth reaches Earth through empty space.
🖼️ See it
While a substance changes state the temperature stays flat: the heat goes into breaking the bonds between particles, not into speeding them up.
📝 Worked examples
°F = °C × 9/5 + 32
100 °C → 212 °F
20 °C → 68 °F
K = °C + 273
27 °C = 300 K
Three ways heat travels:conduction (through solids, touching), convection (in liquids and gases that circulate), radiation (as waves, even through a vacuum).
Temperature measures the average kinetic energy of particles. Heat is energy that flows from hot to cold.
✏️ Quick check · 1 of 10
Define conduction
Heat transfer through direct contact between objects is called:
Think of a metal spoon in hot soup.
✍️ Type your answer · 2 of 10
Convert the temperature.
What is 20°C in Fahrenheit?
Enter an exact answer, without rounding.
°F
°F = °C × 9/5 + 32.
✏️ Quick check · 3 of 10
Where convection happens
Convection happens mainly in which states of matter?
The particles need to be able to flow.
✍️ Type your answer · 4 of 10
Convert the temperature.
What is 100°C in Fahrenheit?
Enter an exact answer, without rounding.
°F
°F = °C × 9/5 + 32.
✏️ Quick check · 5 of 10
An example of radiation
Which of these is an example of heat transfer by radiation?
Radiation can travel through empty space.
✍️ Type your answer · 6 of 10
Convert the temperature.
What is 0°C in Fahrenheit?
Enter an exact answer, without rounding.
°F
Multiply by 9/5 first: 0 × anything is 0. Then add 32.
✏️ Quick check · 7 of 10
Direction
Heat naturally flows from:
Think of a hot drink cooling down.
✏️ Quick check · 8 of 10
Vacuum
Which way can heat travel through a vacuum?
How does sunlight reach Earth?
✍️ Type your answer · 9 of 10
Convert using °F = °C × 9/5 + 32.
What is 0 °C in °F?
Enter an exact answer, without rounding.
°F
The first term becomes 0.
✍️ Type your answer · 10 of 10
Convert using °F = °C × 9/5 + 32.
What is 30 °C in °F?
Enter an exact answer, without rounding.
°F
Multiply by 1.8, then add 32.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
Convection happens in:
Question 2 of 5
Which material is a good conductor of heat?
Question 3 of 5
Water boils at what temperature at sea level?
Question 4 of 5
The Sun's heat reaches the Earth by:
Question 5 of 5
0 °C is equal to how many kelvin?
Lesson 9 · Energy
🌌 Energy Resources
The energy we use every day comes from resources that are either renewable — naturally replenished — or non-renewable, meaning limited and slow to form.
🌌 Renewable vs. non-renewable resources
Renewable resources — like solar, wind, hydro (water), and geothermal energy — replenish naturally and won't run out on human timescales.
Non-renewable resources, also called fossil fuels — coal, oil, and natural gas — form over millions of years from ancient organic material. Burning them releases their stored energy, but also produces pollution.
Renewable
Non-renewable
📝 Worked examples
Renewable: solar, wind, hydro, geothermal, biomass
Non-renewable: coal, oil, natural gas, nuclear fuel
efficiency = (useful energy out ÷ total energy in) × 100
40 J useful out of 100 J in → 40%
Burning fossil fuels releases CO₂, which adds to climate change. Wind and solar do not release CO₂ when running, but depend on weather. Nuclear power emits no CO₂ but produces radioactive waste.
No device is 100% efficient. Some energy always ends up as waste heat.
✏️ Quick check · 1 of 10
Solar and wind power
Solar and wind power are examples of:
The sun and wind will not run out.
✏️ Quick check · 2 of 10
Coal, oil, and natural gas
Coal, oil, and natural gas are collectively known as:
They formed from plants and animals that died millions of years ago.
✏️ Quick check · 3 of 10
Defining renewable resources
A renewable resource is best defined as one that:
Renew means to make new again.
✍️ Type your answer · 4 of 10
Solar, wind, hydro, and geothermal are the renewable resources named in this lesson.
How many renewable resources are named?
Enter an exact answer, without rounding.
Count the resources in the list.
✍️ Type your answer · 5 of 10
Coal, oil, and natural gas are the fossil fuels named in this lesson.
How many fossil fuels are named?
Enter an exact answer, without rounding.
Count the fuels in the list.
✍️ Type your answer · 6 of 10
Energy resources are grouped into renewable and non-renewable.
How many total categories of energy resources are there?
Enter an exact answer, without rounding.
Renewable and non-renewable.
✏️ Quick check · 7 of 10
Renewable
Which energy source is renewable?
Which one will not run out?
✏️ Quick check · 8 of 10
Fossil fuel
Burning fossil fuels mainly releases:
Carbon in fuel combines with oxygen.
✍️ Type your answer · 9 of 10
A machine takes in 120 J and gives out 30 J of useful energy.
What is its efficiency?
Enter an exact answer, without rounding.
%
Divide useful by total, then × 100.
✍️ Type your answer · 10 of 10
A lamp turns 200 J of electrical energy into 60 J of light.
What is its efficiency?
Enter an exact answer, without rounding.
%
Divide useful by total, then × 100.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
Hydroelectric power uses:
Question 2 of 5
Solar panels convert:
Question 3 of 5
Which is non-renewable?
Question 4 of 5
A disadvantage of wind power is that it:
Question 5 of 5
Nuclear power stations do not release CO₂ but they do produce:
Lesson 10 · Waves
🌊 Waves
A wave carries energy from one place to another without carrying matter along with it. Sound, light, and ripples on a pond are all waves.
🔋 Parts of a wave
The wavelength is the distance between one point on a wave and the same point on the next repeat. The amplitude is the height of the wave from its resting position — it relates to how much energy the wave carries.
amplitude = wave heightwavelength = distance per repeat
🏃 Wave speed
speed = frequency × wavelength
frequency = 5 Hz, wavelength = 2 m
speed = 5 × 2 = 10 m/s
Frequency is measured in hertz (Hz) — the number of wave cycles that pass a point every second.
🎤 Sound is a longitudinal wave
In a transverse wave (like light or ripples), particles move up and down, perpendicular to the wave's direction. In a longitudinal wave (like sound), particles squeeze and stretch back and forth in the same direction the wave travels.
📝 Worked examples
wave speed = frequency × wavelength
f = 5 Hz, λ = 3 m → v = 15 m/s
period T = 1 ÷ f
f = 4 Hz → T = 0.25 s
Transverse waves vibrate at right angles to their travel (light, ripples). Longitudinal waves vibrate along their travel (sound).
Waves transfer energy, not matter. A cork on a pond bobs up and down but does not travel with the wave.
✏️ Quick check · 1 of 10
Define wavelength
Wavelength measures:
Measure from one crest to the next crest.
✍️ Type your answer · 2 of 10
A wave has a frequency of 5 Hz and a wavelength of 2 m.
What is its speed, in m/s?
Enter an exact answer, without rounding.
m/s
Wave speed = frequency × wavelength: 5 × 2.
✏️ Quick check · 3 of 10
Classify sound waves
Sound is what type of wave?
The air vibrates back and forth along the direction the sound travels.
✍️ Type your answer · 4 of 10
A wave has a frequency of 10 Hz and a wavelength of 3 m.
What is its speed, in m/s?
Enter an exact answer, without rounding.
m/s
Wave speed = frequency × wavelength: 10 × 3.
✏️ Quick check · 5 of 10
What amplitude relates to
For a sound wave, a bigger amplitude means:
Amplitude is the size of the vibration.
✍️ Type your answer · 6 of 10
A wave travels at 20 m/s with a wavelength of 4 m.
What is its frequency, in Hz?
Enter an exact answer, without rounding.
Hz
Frequency = speed ÷ wavelength: 20 ÷ 4.
✏️ Quick check · 7 of 10
Sound wave
Sound is what type of wave?
It is a pressure wave.
✏️ Quick check · 8 of 10
Amplitude
A wave's amplitude is related to its:
Think of a big wave versus a small ripple.
✍️ Type your answer · 9 of 10
A wave has frequency 20 Hz and wavelength 0.5 m.
What is its speed?
Enter an exact answer, without rounding.
m/s
v = fλ.
✍️ Type your answer · 10 of 10
A sound wave travels at 340 m/s with a wavelength of 2 m.
What is its frequency?
Enter an exact answer, without rounding.
Hz
Divide speed by wavelength.
📝 Lesson quiz · 5 questions
0 / 5
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Question 1 of 5
Wavelength is the distance between:
Question 2 of 5
Frequency is measured in:
Question 3 of 5
Which wave is transverse?
Question 4 of 5
If the speed stays the same and frequency increases, wavelength:
Question 5 of 5
What is the period of a 4 Hz wave?
Lesson 11 · Waves
🔊 Sound
Sound is a wave that needs a medium to travel through — unlike light, it can't travel through empty space.
🔋 Compressions and rarefactions
Sound waves are longitudinal waves, made of compressions (particles pushed together) and rarefactions (particles spread apart) — unlike the up-and-down transverse waves you saw earlier.
Pitch depends on frequency (higher frequency = higher pitch), and loudness depends on amplitude. Sound travels at about 343 m/s in air, but faster through liquids and solids.
lines close together = compressionlines spread apart = rarefaction
🏃 Speed of sound
speed = frequency × wavelength
frequency = 100 Hz, wavelength = 3 m
speed = 100 × 3 = 300 m/s
📝 Worked examples
Speed of sound in air ≈ 340 m/s
distance = speed × time
Thunder heard 3 s after lightning → 340 × 3 = 1020 m away
Echo: sound travels there AND back.
Echo after 2 s → total path 680 m → wall is 340 m away
Pitch depends on frequency (high frequency = high pitch). Loudness depends on amplitude. Sound cannot travel through a vacuum.
✏️ Quick check · 1 of 10
What sound needs to travel
Sound waves need a ___ to travel through.
There is no sound in space.
✏️ Quick check · 2 of 10
What determines pitch
Pitch is determined mainly by a sound wave's:
More vibrations per second give a higher note.
✏️ Quick check · 3 of 10
Type of wave
Sound waves are what type of wave?
Its vibrations squash and stretch the air.
✍️ Type your answer · 4 of 10
Use speed = frequency × wavelength. A sound wave has a frequency of 100 Hz and a wavelength of 3 m.
What is its speed, in m/s?
Enter an exact answer, without rounding.
m/s
Speed = frequency × wavelength: 100 × 3.
✍️ Type your answer · 5 of 10
Use speed = frequency × wavelength. A sound wave has a frequency of 50 Hz and a wavelength of 4 m.
What is its speed, in m/s?
Enter an exact answer, without rounding.
m/s
Speed = frequency × wavelength: 50 × 4.
✍️ Type your answer · 6 of 10
Use speed = frequency × wavelength. A sound wave has a frequency of 340 Hz and a wavelength of 1 m.
What is its speed, in m/s?
Enter an exact answer, without rounding.
m/s
Speed = frequency × wavelength: 340 × 1.
✏️ Quick check · 7 of 10
Vacuum
Why can't sound travel through space?
What does sound need to travel through?
✏️ Quick check · 8 of 10
Pitch
The pitch of a sound depends on its:
How fast it vibrates.
✍️ Type your answer · 9 of 10
Use 340 m/s for the speed of sound.
How far does sound travel in 2 s?
Enter an exact answer, without rounding.
m
Multiply speed by time.
✍️ Type your answer · 10 of 10
You hear an echo 4 s after shouting at a wall. Use 340 m/s.
How far away is the wall?
Enter an exact answer, without rounding.
m
The sound travels to the wall AND back.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
Sound travels fastest through:
Question 2 of 5
Loudness depends on the wave's:
Question 3 of 5
Loudness is measured in:
Question 4 of 5
Ultrasound has a frequency:
Question 5 of 5
The range of human hearing is about:
Lesson 12 · Light
💡 Light & Optics
Light travels in straight lines until it hits something. What happens next — bouncing off or bending through — follows precise, predictable rules.
🧝 The law of reflection
When light bounces off a surface, the angle of incidence (the incoming ray) always equals the angle of reflection (the outgoing ray), both measured from an imaginary line called the normal.
angle of incidence (i) = angle of reflection (r)
🌊 Refraction
Refraction is the bending of light as it passes from one material into another — like air into water. This bending happens because light travels at different speeds in different materials, which is why a straw looks "bent" in a glass of water.
🔬 Mirrors & lenses
Convex lens
Curves outward; bends light rays together (converges them).
Law of reflection: angle of incidence = angle of reflection
Incidence 35° from the normal → reflection 35°
Refraction: light bends when it changes speed.
Air → glass: bends TOWARD the normal (slows down)
Glass → air: bends AWAY from the normal
A convex lens converges (brings together) parallel rays. A concave lens spreads them apart. Light travels about 300 000 km/s.
Angles are measured from the normal — the line at 90° to the surface — not from the surface itself.
✏️ Quick check · 1 of 10
The law of reflection
According to the law of reflection:
Light bounces off at the same angle it arrives.
✏️ Quick check · 2 of 10
Define refraction
Refraction is best described as:
Think of a straw that looks bent in a glass of water.
✏️ Quick check · 3 of 10
Convex vs. concave
Which type of lens bends light rays together?
Convex lenses bulge outwards and focus light to a point.
✍️ Type your answer · 4 of 10
A light ray hits a mirror with an angle of incidence of 30°.
What is the angle of reflection, in degrees?
Enter an exact answer, without rounding.
degrees
The angle of reflection equals the angle of incidence.
✏️ Quick check · 5 of 10
Luminous objects
An object that makes its own light, like the Sun, is called:
Lumen means light: it gives out its own light.
✍️ Type your answer · 6 of 10
A light ray hits a mirror with an angle of incidence of 45°.
What is the angle of reflection, in degrees?
Enter an exact answer, without rounding.
degrees
The angle of reflection equals the angle of incidence.
✏️ Quick check · 7 of 10
Reflection
The law of reflection says that:
The angles are equal.
✏️ Quick check · 8 of 10
Refraction
Refraction happens because light:
Think about entering water.
✍️ Type your answer · 9 of 10
A ray hits a mirror at 40° to the normal.
What is the angle of reflection (degrees)?
Enter an exact answer, without rounding.
°
They are equal.
✍️ Type your answer · 10 of 10
A ray makes 30° with the mirror surface.
What is the angle of incidence (degrees)? (Hint: the normal is at 90° to the surface.)
Enter an exact answer, without rounding.
°
Measure from the normal, not the surface.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
A plane (flat) mirror forms an image that is:
Question 2 of 5
A convex lens:
Question 3 of 5
Approximately how fast does light travel?
Question 4 of 5
A straw looks bent in a glass of water because of:
Question 5 of 5
The "normal" is a line that is:
Lesson 13 · Light
🌈 Light: Shadows, Pinhole Cameras & the Colour Spectrum
Light's tendency to travel in perfectly straight lines explains everything from why shadows form to how a simple box with a tiny hole can take a picture — and why white light secretly contains every colour.
📸 Straight lines, shadows, and pinholes
Light travels in straight lines, a property called rectilinear propagation. Because of this, an opaque object blocks light and creates a shadow behind it.
A pinhole camera uses a tiny hole to let light rays cross and form an upside-down image, which proves light travels in straight lines.
White light is actually a mix of all colours — when it passes through a triangular prism, it separates (disperses) into the visible spectrum, remembered as ROYGBIV (red, orange, yellow, green, blue, indigo, violet), because each colour bends by a slightly different amount.
A prism splits white light into the ROYGBIV spectrum because each colour bends by a different amount.
📝 Worked examples
Opaque: blocks light (wood)
Translucent: lets some through (frosted glass)
Transparent: lets nearly all through (clear glass)
Visible spectrum (ROYGBIV): red, orange, yellow, green, blue, indigo, violet
Red = longest wavelength, violet = shortest
Sun → Earth: 150 000 000 km ÷ 300 000 km/s = 500 s
Shadows form because light travels in straight lines. A solar eclipse is the Moon's shadow falling on Earth.
White light is a mixture of all colours. A prism splits it by refraction (dispersion).
✏️ Quick check · 1 of 9
Rectilinear propagation
Light travels in:
Light cannot go round corners.
✏️ Quick check · 2 of 9
Why shadows form
A shadow forms because:
An opaque object stops light passing through.
✏️ Quick check · 3 of 9
Why a prism makes a rainbow
A prism separates white light into a rainbow of colours because:
The colours slow down by different amounts in the glass.
✍️ Type your answer · 4 of 9
The visible spectrum is often remembered by the acronym ROYGBIV.
How many colours are in the visible spectrum according to ROYGBIV?
Enter an exact answer, without rounding.
Count the letters in ROYGBIV.
✍️ Type your answer · 5 of 9
A pinhole camera uses a tiny hole to let light rays cross and form an image.
How many holes does a basic pinhole camera use?
Enter an exact answer, without rounding.
It is in the name: pinhole.
✏️ Quick check · 6 of 9
Why shadows
Shadows form because light:
Think of how light moves.
✏️ Quick check · 7 of 9
Wavelength
Which visible colour has the longest wavelength?
ROYGBIV starts with it.
✍️ Type your answer · 8 of 9
The visible spectrum is remembered as ROYGBIV.
How many colours does it contain?
Enter an exact answer, without rounding.
Count the letters in ROYGBIV.
✍️ Type your answer · 9 of 9
Sunlight travels 150 000 000 km at 300 000 km/s.
How many seconds does it take to reach Earth?
Enter an exact answer, without rounding.
s
Divide distance by speed.
📝 Lesson quiz · 5 questions
0 / 5
Re-read the lesson, then give it another go.
Question 1 of 5
Which of these is transparent?
Question 2 of 5
What splits white light into colours?
Question 3 of 5
A solar eclipse happens when:
Question 4 of 5
Which visible light has the shortest wavelength?
Question 5 of 5
An object that blocks all light is:
Lesson 14 · Electricity
🔋 Electrostatics: Charges & Static Electricity
Before current flows through a circuit, charge can build up and just sit still — this is static electricity, and it follows the exact same attract/repel rules as magnets.
⚡ Charges attract and repel
Objects build up an electric charge (positive or negative), usually by rubbing two materials together (like a balloon on hair), which transfers electrons between them.
Like charges repel (push apart); opposite charges attract (pull together) — the same rule as magnetic poles.
Static electricity is charge that stays in place until it discharges (like a spark, or lightning), unlike current electricity, where charge flows continuously.
Like charges repel
Opposite charges attract
📝 Worked examples
Like charges repel; opposite charges attract.
Rubbing a balloon on hair transfers electrons to the balloon:
balloon gains electrons → negative
hair loses electrons → positive
Object with 8 protons and 6 electrons: net charge = +2
Object with 5 protons and 7 electrons: net charge = −2
Only electrons move; protons stay in the nucleus. Insulators (plastic, rubber) hold charge. Conductors (metals) let it flow.
Lightning is a huge static discharge. A lightning rod gives it a safe path to the ground.
✏️ Quick check · 1 of 9
Like charges
Two objects with the same type of charge (both positive, or both negative) will:
Like charges behave like like poles on a magnet.
✏️ Quick check · 2 of 9
Opposite charges
An object with a positive charge and an object with a negative charge will:
Opposites attract.
✏️ Quick check · 3 of 9
How static charge builds up
Static electricity usually builds up when two materials are:
Friction moves electrons from one material to the other.
✍️ Type your answer · 4 of 9
There are two types of electric charge.
How many types of electric charge are there (positive and negative)?
Enter an exact answer, without rounding.
Positive and negative.
✍️ Type your answer · 5 of 9
A balloon rubbed on hair takes 5 units of negative charge from the hair, which had 0 units of charge before. Because charge is conserved, the hair ends up with the same amount of positive charge that the balloon gained in negative charge.
How many units of positive charge does the hair now have?
Enter an exact answer, without rounding.
Charge is conserved: what the balloon gains, the hair loses.
✏️ Quick check · 6 of 9
Rule
Two positively charged objects will:
Like charges push apart.
✏️ Quick check · 7 of 9
Moving charge
Which particle moves when objects are charged by rubbing?
Protons are locked in the nucleus.
✍️ Type your answer · 8 of 9
An object has 8 protons and 6 electrons. Charge is measured in units of e.
What is the net charge?
Enter an exact answer, without rounding.
Protons count +1 each and electrons −1 each.
✍️ Type your answer · 9 of 9
An object has 5 protons and 7 electrons.
What is the net charge in units of e?
Enter an exact answer, without rounding.
There are more negative than positive charges.
📝 Lesson quiz · 5 questions
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Question 1 of 5
The unit of electric charge is the:
Question 2 of 5
Which material is a good insulator?
Question 3 of 5
Lightning is caused by:
Question 4 of 5
A lightning rod:
Question 5 of 5
A neutral object becomes negatively charged when it:
Lesson 15 · Electricity & Magnetism
🧲 Magnetism
Magnets and electricity are deeply connected — electric current can create magnetism, which is the basis for electromagnets, motors, and generators.
🧲 Poles and fields
Every magnet has two poles, North and South. Like poles repel, and opposite poles attract. Magnetic field lines flow from the North pole to the South pole outside the magnet.
An electromagnet is made by wrapping a coil of wire around an iron core and running electric current through it — more coils or more current makes it stronger, and unlike a permanent magnet, it can be switched on and off.
Like poles repel
Opposite poles attract
📝 Worked examples
Like poles repel (N–N, S–S); unlike poles attract (N–S).
Cut a bar magnet in half → two smaller magnets, each with N and S.
Magnetic materials: iron, nickel, cobalt, steel
Not magnetic: aluminium, copper, plastic, wood
Field lines run from north to south outside the magnet, and they are closest together where the field is strongest. A compass needle lines up with Earth's magnetic field.
Electromagnet = coil + current + iron core. More turns or more current makes it stronger, and switching the current off switches the magnet off.
✏️ Quick check · 1 of 10
Like poles
Two like magnetic poles (N and N, or S and S) will:
Like poles push apart.
✏️ Quick check · 2 of 10
Opposite poles
A north pole and a south pole placed near each other will:
Opposite poles pull together.
✏️ Quick check · 3 of 10
Making an electromagnet
An electromagnet is created by:
Electric current in a coil makes a magnetic field.
✍️ Type your answer · 4 of 10
An electromagnet's coil has 10 loops of wire. Doubling the number of loops makes it stronger.
If the number of loops is doubled, how many loops will there be?
Enter an exact answer, without rounding.
loops
Double 10.
✍️ Type your answer · 5 of 10
An electromagnet uses 5 A of current, and doubling the current makes it stronger.
If the current is doubled, what is the new current, in amps?
Enter an exact answer, without rounding.
A
Double 5.
✍️ Type your answer · 6 of 10
Think about the basic structure of any magnet.
How many poles does every magnet have?
Enter an exact answer, without rounding.
North and south.
✏️ Quick check · 7 of 10
Magnetic?
Which material is attracted to a magnet?
Think of what sticks to a fridge magnet.
✏️ Quick check · 8 of 10
Poles
Two north poles brought close together will:
Like repels like.
✍️ Type your answer · 9 of 10
A bar magnet is cut in half.
How many poles are there in total across the two pieces?
Enter an exact answer, without rounding.
Each new piece is a complete magnet.
✍️ Type your answer · 10 of 10
Every magnet has a north and a south pole.
How many poles does a horseshoe magnet have?
Enter an exact answer, without rounding.
Magnets always have a north and a south.
📝 Lesson quiz · 5 questions
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Question 1 of 5
Which pair will attract?
Question 2 of 5
Which is NOT attracted to a magnet?
Question 3 of 5
A compass needle points north because:
Question 4 of 5
How can you make an electromagnet stronger?
Question 5 of 5
Outside a magnet, field lines point from:
Lesson 16 · Electricity
🔌 Electricity & Circuits
Electric current is the flow of charge through a circuit — a complete loop from a power source, through a device, and back again.
🔌 A simple circuit
A circuit needs a complete, unbroken loop: a power source (like a battery), wires, and something that uses the electricity (like a bulb).
power sourceload (bulb)
⚡ Ohm's law
Voltage = current × resistance (V = IR)
current = 2 A, resistance = 5 Ω
Voltage = 2 × 5 = 10 V
🔗 Series vs. parallel circuits
Series circuit
One single loop. If one device fails, the whole circuit stops working.
Parallel circuit
Multiple branches. Each device works independently, even if another one fails.
📝 Worked examples
Ohm's law: V = I × R
12 V across 4 Ω → I = 12 ÷ 4 = 3 A
Series: resistances add 2 Ω + 3 Ω = 5 Ω
Parallel: each branch gets the full voltage
Power: P = V × I = 12 × 3 = 36 W
In a series circuit the current is the same everywhere. In a parallel circuit the current splits, and if one branch breaks the others keep working.
Meters: an ammeter measures current and is connected in series. A voltmeter measures voltage and is connected in parallel.
✍️ Type your answer · 1 of 10
A circuit has a current of 2 A and a resistance of 5 Ω.
What is the voltage, in volts?
Enter an exact answer, without rounding.
V
V = I × R: 2 × 5.
✏️ Quick check · 2 of 10
Series vs. parallel
In which type of circuit does everything stop working if one bulb burns out?
In this circuit there is only one path for the current.
✍️ Type your answer · 3 of 10
A circuit has a voltage of 12 V and a resistance of 4 Ω.
What is the current, in amps?
Enter an exact answer, without rounding.
A
I = V ÷ R: 12 ÷ 4.
✏️ Quick check · 4 of 10
Conductors vs. insulators
Which material is a good electrical conductor?
Electrical wires are made of it.
✍️ Type your answer · 5 of 10
A circuit has a current of 3 A and a resistance of 10 Ω.
What is the voltage, in volts?
Enter an exact answer, without rounding.
V
V = I × R: 3 × 10.
✏️ Quick check · 6 of 10
Unit of resistance
Electrical resistance is measured in:
The symbol is Ω, named after Georg Ohm.
✏️ Quick check · 7 of 10
Ammeter
An ammeter is connected:
The current must pass through the meter.
✏️ Quick check · 8 of 10
Parallel
In a parallel circuit, if one bulb breaks:
Think of house wiring.
✍️ Type your answer · 9 of 10
A 9 V battery is connected across a 3 Ω resistor.
What is the current?
Enter an exact answer, without rounding.
A
Divide voltage by resistance.
✍️ Type your answer · 10 of 10
A current of 2 A flows through a 5 Ω resistor.
What is the voltage across it?
Enter an exact answer, without rounding.
V
Multiply current by resistance.
📝 Lesson quiz · 5 questions
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Re-read the lesson, then give it another go.
Question 1 of 5
The unit of resistance is the:
Question 2 of 5
In a series circuit the current is:
Question 3 of 5
Two resistors of 4 Ω and 6 Ω are in series. What is the total resistance?
Question 4 of 5
What is the power of a device with 6 V and 2 A?
Question 5 of 5
A switch in a circuit:
Final Challenge
🏆 26-Question Challenge Quiz
One question from every topic you just learned. Pick an answer for each question, then hit Check My Answers.
0 / 26
💪 Keep practicing — go back through the lessons and retake the quiz!
Q1 · Motion & Speed
A runner covers 100 km in 2 hours. What is their speed?
Q2 · Forces
A 6 kg object accelerates at 3 m/s². What force acts on it?
Q3 · Gravity & Weight
Use g = 10 m/s². What is the weight of a 7 kg object?
Q4 · Energy
A 3 kg object moves at 4 m/s. What is its kinetic energy?
Q5 · Work & Machines
A force of 25 N moves an object 4 m. How much work is done?
Q6 · Heat & Temperature
What is 25°C in Fahrenheit?
Q7 · Waves
A wave has a frequency of 8 Hz and a wavelength of 5 m. What is its speed?
Q8 · Light & Optics
A light ray hits a mirror with a 60° angle of incidence. What is the angle of reflection?
Q9 · Electricity
A circuit has a current of 5 A and a resistance of 6 Ω. What is the voltage?
Q10 · Newton's Laws
Which law states "for every action, there is an equal and opposite reaction"?
Q11 · Motion & Speed
A cyclist speeds up from 10 m/s to 30 m/s in 4 s. What is the acceleration?
Q12 · Forces & Newton's Laws
An unbalanced force on an object causes:
Q13 · Types of Forces: Friction, Contact & Non-Contact
A skydiver reaches terminal velocity when:
Q14 · Pressure
Atmospheric pressure at the top of a mountain, compared with sea level, is:
Q15 · Gravity & Weight
In deep space, far from any planet, a 5 kg object has:
Q16 · Energy: Types & Forms
What is the PE of a 10 kg object raised 1 m (g = 10)?
Q17 · Work & Simple Machines
Power is:
Q18 · Heat & Temperature
0 °C is equal to how many kelvin?
Q19 · Energy Resources
Nuclear power stations do not release CO₂ but they do produce:
Q20 · Waves
What is the period of a 4 Hz wave?
Q21 · Sound
The range of human hearing is about:
Q22 · Light & Optics
The "normal" is a line that is:
Q23 · Light: Shadows, Pinhole Cameras & the Colour Spectrum