Physics

Electric current is the flow of charge around a circuit, measured in amperes (A). Voltage (potential difference) is the energy given to each unit of charge by the battery, measured in volts (V). Ohm's Law connects current, voltage, and resistance.

Every electrical circuit is made up of components such as wires, batteries, bulbs, switches, and resistors. Each component has a standard symbol used in circuit diagrams. Knowing these symbols lets you read and draw circuits correctly.

Electricity can be dangerous if used incorrectly. Safety features like fuses, circuit breakers, and earthing protect people and appliances from damage. Understanding why we use these features helps prevent accidents at home and at school.

Electrical power tells us how fast energy is being transferred in a circuit. It is calculated using P = IV (power equals current times voltage). Electrical energy is simply power multiplied by time, measured in joules or kilowatt-hours.

The relationship between voltage, current, and resistance in electric circuits.

In a parallel circuit components are connected across the same two points, giving multiple paths for current. Voltage is the same across all branches but currents add up.

In a series circuit all components are connected end-to-end in a single loop. The same current flows through every component, but voltages add up.

Study of electric charge, current, circuits, and magnetic fields and their interactions.

Magnets have two poles — north and south. Like poles repel and unlike poles attract. Every magnet is surrounded by a magnetic field that can be shown using field lines. Magnetic fields can be created by electric currents in a wire (electromagnetism).

An object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces.

How to calculate density and use Archimedes' principle to determine if objects float or sink.

How forces combine, what balanced forces mean for motion, and how to draw force diagrams.

Friction is a force that opposes relative motion between surfaces in contact. Learn about static and kinetic friction.

Gravity is an attractive force between all objects with mass. Near Earth's surface, gravity pulls objects downward with a gravitational field strength of approximately 10 N/kg. Weight is the gravitational force on an object and is calculated using W = mg. Weight and mass are different quantities.

Momentum is a measure of how difficult it is to stop a moving object. It depends on both mass and velocity. Momentum is always conserved in a closed system — the total momentum before a collision equals the total momentum after.

Newton's three laws form the foundation of classical mechanics, describing how objects move under the influence of forces.

A moment is the turning effect of a force about a pivot. It is calculated by multiplying the force by the perpendicular distance from the pivot. For an object to be balanced (in equilibrium), the total clockwise moments must equal the total anticlockwise moments.

The difference between mass and weight, and how to calculate gravitational force.

The three methods of heat transfer — conduction, convection, and radiation — with everyday examples.

Specific heat capacity tells us how much energy is needed to raise the temperature of 1 kg of a substance by 1°C. Different materials need different amounts of energy to heat up. The formula Q = mcΔT connects energy, mass, specific heat capacity, and temperature change.

Matter exists as a solid, liquid, or gas. The particle model explains the properties of each state. Solids have fixed shape and volume; liquids flow but have fixed volume; gases fill their container. Changes between states involve energy being transferred.

Temperature is a measure of how hot or cold something is. Scientists use the Kelvin scale, which starts at absolute zero, while everyday life uses Celsius. Converting between them requires adding or subtracting 273.

Most materials expand when heated and contract when cooled. This is called thermal expansion, and it happens because particles vibrate more at higher temperatures.

Study of motion, forces, energy, and how objects interact, providing foundation for understanding the physical world.

Uniformly accelerated motion described by the kinematic equations relating displacement, velocity, acceleration, and time.

How to calculate average speed, distance, and time using the speed-distance-time triangle.

Distance is the total length of path travelled, regardless of direction — it is a scalar quantity. Displacement is the straight-line distance from start to finish, including direction — it is a vector quantity. Understanding the difference is essential in physics.

A distance–time graph shows how the distance of an object from a starting point changes over time. The gradient (slope) of the line gives the speed. A straight line means constant speed, a curved line means changing speed, and a horizontal line means the object is stationary.

Objects in free fall accelerate at g ≈ 9.8 m/s² downward. Projectile motion combines horizontal uniform motion with vertical free fall.

Uniform motion describes movement at constant velocity. Distance, speed, and time are related by d = vt.

Velocity is a vector quantity that describes both the speed and direction of motion. It differs from speed, which only has magnitude. Average velocity is calculated as displacement divided by time. Objects moving in opposite directions have opposite signs of velocity.

Atmospheric pressure is the pressure exerted by the weight of Earth's atmosphere above us. At sea level it equals about 101 325 Pa (1 atm).

Gas pressure results from particles colliding with the walls of a container. Pressure increases when the temperature rises or when the volume decreases. Boyle's Law states that for a fixed mass of gas at constant temperature, pressure and volume are inversely proportional.

Hydrostatic pressure is the pressure exerted by a fluid at rest due to the weight of fluid above it. It increases with depth.

Definition of pressure, how area affects pressure, and the formula P = F/A.

An inclined plane is a flat surface tilted at an angle. It reduces the force needed to lift an object by spreading the work over a longer distance.

A lever is a simple machine consisting of a rigid bar pivoting on a fulcrum. It can multiply force or distance, depending on where the load, effort, and fulcrum are placed.

How fixed and movable pulleys work, the load-effort relationship, and mechanical advantage.

The wheel and axle is a simple machine consisting of a large wheel attached to a smaller axle. Applying a force to the larger wheel produces a larger force at the axle, making it easier to turn heavy loads. Examples include steering wheels, door knobs, and screwdrivers.

The total mechanical energy of an isolated system remains constant. Energy transforms between kinetic and potential forms.

Gravitational potential energy (GPE) is the energy stored by an object due to its height above the ground. The greater the height and mass, the more GPE it has. As an object falls, its GPE converts to kinetic energy.

Kinetic energy is the energy an object has because of its motion. It depends on the object's mass and the square of its speed. Doubling the speed quadruples the kinetic energy. The kinetic energy of an object can be transferred to other forms when it stops.

What power means in physics, how to calculate it, and the difference between energy and power.

Work is done when a force causes displacement. The work-energy theorem connects net work to change in kinetic energy.

Study of wave motion, light behavior, and optical phenomena including reflection, refraction, and electromagnetic spectrum.

How white light splits into a spectrum, colour mixing, and how filters and objects appear coloured.

The electromagnetic spectrum is the range of all types of electromagnetic radiation, ordered by wavelength and frequency. It includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. All EM waves travel at the speed of light in a vacuum.

When light hits a smooth surface, it reflects so that the angle of incidence equals the angle of reflection. Both angles are measured from the normal to the surface.

Lenses refract (bend) light by using curved transparent surfaces. Convex (converging) lenses focus parallel light rays to a focal point. Concave (diverging) lenses spread light rays outward. Lenses are used in glasses, cameras, microscopes, and telescopes.

Mirrors reflect light according to the law of reflection — the angle of incidence equals the angle of reflection. Plane mirrors produce virtual, upright images the same size as the object. Concave mirrors converge light and can magnify; convex mirrors diverge light and give a wider field of view.

Refraction is the bending of light as it passes from one medium to another. The bending occurs because light travels at different speeds in different materials.

When light travels from a denser medium to a less dense medium at an angle greater than the critical angle, it is completely reflected back — this is total internal reflection (TIR). TIR is the principle behind optical fibres used in telecommunications and medicine.

Sound is a longitudinal wave that requires a medium to travel. Pitch depends on frequency — higher frequency means higher pitch. Loudness depends on amplitude — greater amplitude means louder sound. Sound travels faster in solids and liquids than in gases.

All waves share common properties. Wavelength is the length of one complete wave cycle, frequency is the number of waves per second, and amplitude is the maximum displacement from rest. These properties are related by the wave speed equation v = fλ.