Cambridge IGCSE Physics 0625 – Unit Summaries

Free overview of every unit in the Cambridge IGCSE Physics (0625) syllabus, written by Dr. Khaled Dabour for Dabour Hub students. Each unit below starts with the key ideas you need to know. The complete revision notes, diagrams, quizzes and question banks are available to registered students.

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1. Motion, forces and energy – IGCSE Physics 0625

Scalars and vectors The two motion graphs On a speed–time graph a horizontal line means constant speed, a straight slope means constant acceleration, and a curve means changing acceleration. The core equations Forces A resultant force changes the speed or the direction of motion. If the resultant force is zero the object stays at rest or keeps moving at constant velocity. Terminal velocity: a falling object accelerates, drag rises with speed, and when…

2. Thermal physics – IGCSE Physics 0625

Kinetic particle model Temperature is a measure of the average kinetic energy of the particles. Gas pressure comes from particles colliding with the container walls and changing momentum. The gas relationships Temperature must always be in kelvin: K = °C + 273. Absolute zero, 0 K or −273 °C, is where particle motion is a minimum. Expansion Heating makes particles vibrate more and push each other further apart, so the material…

3. Waves – IGCSE Physics 0625

The wave words What happens at a boundary Reflection: the angle of incidence equals the angle of reflection, both measured from the normal. A plane mirror gives an image that is virtual, upright, the same size, and as far behind the mirror as the object is in front, laterally inverted. Refraction: light entering a denser medium slows down and bends towards the normal; leaving it, it speeds up and bends away. n = sin i ÷ sin r. Diffraction is greatest when the gap is about the same size as the wavelength. Total internal reflection It happens when light travels from a…

4. Electricity and magnetism – IGCSE Physics 0625

Circuit quantities at a glance How a current is delivered Cell pushes → charge flows → p.d. across component → work done → energy transferred → charge returns A current is the rate of flow of charge, I = Q/t. In a metal the carriers are free electrons; they drift from negative to positive, while conventional current is drawn from positive to negative. The e.m.f. of a supply is the energy given to each coulomb; the p.d. across a component is the energy taken from each coulomb. Resistance and what changes it A fixed resistor at constant temperature obeys Ohm’s law, so…

5. Nuclear physics – IGCSE Physics 0625

The atom and its nucleus An atom has a tiny, dense nucleus of protons and neutrons, surrounded by electrons in shells. The proton number Z names the element; the nucleon number A is protons plus neutrons. Isotopes of one element have the same Z but different A, so they behave identically in chemistry but differ in stability. Rutherford scattering: alpha particles fired → most pass straight through → a few deflected → very few bounce back → atom is mostly empty space with a small positive nucleus The three emissions compared Decay equations In alpha decay A falls by 4 and Z…

6. Space physics – IGCSE Physics 0625

The Solar System in order Sun → Mercury → Venus → Earth → Mars → asteroid belt → Jupiter → Saturn → Uranus → Neptune The further a planet is from the Sun, the weaker the gravitational field strength there, the slower its orbital speed and the longer its year. Orbital speed is v = 2πr ÷ T. Why orbits happen Gravity provides a force towards the centre, so the planet is always accelerating even at steady speed. A comet’s orbit…