O Level Physics Topical Revision Notes

Vocabulary flashcards covering Topics 1-22 from the O Level Physics revision notes.

Physical quantity

A measurable quantity that has numerical magnitude and a unit.

Base SI quantities

Fundamental quantities with units: length (m), mass (kg), time (s), current (A), temperature (K), amount of substance (mol).

Derived quantities

Quantities defined by equations in terms of base quantities (e.g., area, volume, density).

Scalar quantity

A quantity that has only magnitude, with no direction.

Vector quantity

A quantity that has both magnitude and direction.

Prefix

A symbol and factor indicating decimal submultiples and multiples (e.g., kilo, milli).

Order of magnitude

Estimate using powers of ten to compare sizes.

Resultant

The vector sum of two or more vectors.

Displacement

A straight-line distance from start to finish in a specific direction.

Distance

Total length travelled, irrespective of direction.

Speed

Rate of change of distance with time.

Velocity

Rate of change of displacement with time; includes direction.

Acceleration

Rate of change of velocity.

Free fall acceleration (g)

Constant acceleration near Earth's surface, ~10 m/s^2.

Terminal velocity

Constant speed when air resistance equals weight.

Newton’s first law

A body at rest or in uniform motion remains so unless acted on by a resultant force.

Newton’s second law

Resultant force equals mass times acceleration (F = ma).

Newton’s third law

For every action, there is an equal and opposite reaction.

Friction

Force opposing motion between surfaces; includes static and kinetic friction.

Moment (torque)

Turning effect of a force: M = F × d.

Centre of gravity (CG)

Point where the weight acts; affects stability.

Principle of moments

For equilibrium, sum of clockwise moments equals sum of anticlockwise moments.

Pressure

Force per unit area (P = F/A).

Hydrostatic pressure

Pressure in a liquid due to depth: P = ρgh plus atmospheric pressure.

Atmospheric pressure

Pressure exerted by air on surfaces; measured by a barometer.

Pascal (Pa)

SI unit of pressure.

Energy

Capacity to do work; includes kinetic, potential, thermal, etc.

Kinetic energy

Energy due to motion: KE = 1/2 mv^2.

Gravitational potential energy

Energy due to height: GPE = mgh.

Work

Force times displacement in the direction of the force: W = F s.

Power

Rate of doing work: P = W/t; or P = F v.

Conservation of energy

Total energy in an isolated system remains constant.

Efficiency

Useful energy output divided by total energy input.

Kinetic model of matter

Molecules in solids, liquids, gases; states differ by particle motion and spacing.

Brownian motion

Random motion of particles due to molecular collisions.

Gas pressure

Pressure from molecules colliding with container walls.

Charles’ Law (qualitative)

At constant mass and pressure, volume ∝ temperature.

Boyle’s Law (qualitative)

At constant temperature, pressure ∝ 1/volume.

Heat transfer types

Conduction, convection, and radiation.

Conduction

Heat transfer by direct contact; metals are good conductors.

Convection

Heat transfer by movement of fluids due to density differences.

Radiation

Heat transfer by electromagnetic waves; does not require a medium.

Temperature

Hotness or coldness; SI unit Kelvin; °C to K: K = °C + 273.15.

Thermometer fixed points

Ice point (0°C) and steam point (100°C) used to calibrate scales.

Specific heat capacity

Energy to raise 1 kg by 1°C: c (J kg^-1 °C^-1).

Latent heat

Energy to change state without temperature change (lf, lv).

Wave

Propagation of energy through a medium as oscillation.

Frequency

Number of waves per second (Hz).

Wavelength

Distance between successive crests or compressions.

Amplitude

Maximum displacement from the rest position.

Wavefront

Line where all points are in phase; can be circular or plane.

Refraction

Bending of light as it passes between media with different speeds; Snell’s law.

Snell’s law

n1 sin i = n2 sin r (two media).

Refractive index

n = c/v; ratio of speed of light in vacuum to speed in the medium.

Total internal reflection

Complete reflection when incident angle exceeds the critical angle.

Critical angle

Angle of incidence in a denser medium for which refraction is 90°.

Converging lens

Lens that focuses light to a focal point; positive focal length.

Diverging lens

Lens that spreads light rays; negative focal length.

Optical fibre

Transmits data via total internal reflection of light.

Electromagnetic spectrum

Range of EM waves from radio to gamma; all travel at c in vacuum.

Transverse vs longitudinal waves

Transverse: particles move perpendicular to the direction of travel; longitudinal: parallel.

Sound

Longitudinal mechanical waves; speed depends on medium.

Echo

Sound reflected from a surface heard after a delay.

Ultrasound

Sound frequency > 20 kHz; used in medical imaging.

Static electricity

Charges accumulate on insulators; transfer by rubbing or induction.

Coulomb’s unit

Unit of charge: coulomb (C).

Electric field

Region where a charge experiences a force; field lines show direction.

Q = It

Charge equals current times time.

Current

Rate of flow of electric charge; measured in amperes (A).

EMF

Work done per unit charge around a circuit; measured in volts.

Resistance

Opposition to current; R = V/I.

Ohm’s Law

V = IR for ohmic conductors at constant temperature.

Series circuit

One path for current; same current through all components; voltage divides.

Parallel circuit

Multiple paths for current; same voltage across branches; currents add.

Practical electricity

Heating effects; P = VI; energy cost; fuses and earthing.

Live, neutral, earth

Live carries current; neutral returns; earth protects from shocks.

Fuse

Safety device that melts under excess current to break the circuit.

Double insulation

Appliance designed to be safe without an earth connection.

Magnet

Material with two poles; like poles repel, unlike attract.

Electromagnet

Coil with iron core producing a magnetic field when current flows.

Magnetic field lines

Lines showing direction of magnetic force; start at North and end at South.

Fleming’s left-hand rule

Rule to determine force, field, and current directions in motors.

D.C. motor

Motor converting electrical energy to kinetic energy; uses split-ring commutator.

Electromagnetic induction

Induction of emf when magnetic flux through a circuit changes (Faraday’s law).

Lenz’s law

Induced current creates a magnetic field opposing the flux change.

AC generator

Generates alternating current by rotating a coil in a magnetic field.

Transformer

Device to step up or down voltage by mutual induction in a core.

Power transmission

High voltage and low current reduce losses in cables.