3 Physics subject content
Seven topics, in the specification’s order and numbering (section 6). They are the content of GCSE Physics without its physics-only parts (including all of Space physics), plus one Higher tier transformer equation.
6.1Energy
Physics Paper 1 · topic 18
6.1.1Energy stores and systems
- A system is an object or a group of objects; describe how the energy stored changes when a system changes (a ball thrown up, a car braking, a kettle boiling).
- Calculate energy changes caused by heating, by forces doing work and by an electric current.
- Kinetic, elastic potential and gravitational potential energy.
- Specific heat capacity: the energy to raise 1 kg by 1 °C.
- Power as the rate of transferring energy or doing work; 1 W is 1 J/s.
- \(E_{\mathrm{k}} = \tfrac{1}{2}mv^2\)
- \(E_{\mathrm{e}} = \tfrac{1}{2}ke^2\)
- \(E_{\mathrm{p}} = mgh\)
- \(\Delta E = mc\Delta\theta\)
- \(P = \dfrac{E}{t}\)
- \(P = \dfrac{W}{t}\)
Required practical 14 · specific heat capacity
6.1.2Conservation and dissipation
- Energy is never created or destroyed; in a closed system the total stays the same.
- Some energy is always dissipated into less useful stores (“wasted”); reduce it with lubrication and thermal insulation.
- Higher thermal conductivity means faster conduction; how wall thickness and conductivity affect how fast a building cools.
- Efficiency as a decimal or a percentage.
- HT Ways to make an energy transfer more efficient.
- \(\text{efficiency} = \dfrac{\text{useful output energy}}{\text{total input energy}}\)
- \(\text{efficiency} = \dfrac{\text{useful power output}}{\text{total power input}}\)
6.1.3National and global energy resources
- Fossil fuels, nuclear fuel, bio-fuel, wind, hydroelectricity, geothermal, tides, the Sun and water waves.
- Renewable against non-renewable; reliability; uses in transport, electricity generation and heating.
- Environmental impact, and trends in how resources are used.
- Science can identify the problems but political, social, ethical and economic factors limit what is done.
- How each resource generates electricity is not needed.
6.2Electricity
Physics Paper 1 · topic 19
6.2.1Current, potential difference and resistance
- Draw and read circuit diagrams with standard symbols.
- Current is the rate of flow of charge, and is the same all round a single loop.
- Ohmic conductors at constant temperature; non-constant resistance of filament lamps, diodes, thermistors and LDRs, and their uses (thermostats, lights that switch on at dusk).
- Measuring resistance with an ammeter and voltmeter; reading I–V graphs.
Required practicals 15 · resistance, and 16 · I–V characteristics
6.2.2Series and parallel circuits
- Series: same current, p.d. shared, resistances add.
- Parallel: same p.d., currents add, total resistance less than the smallest resistor.
- Explain why adding resistors in series raises the total and in parallel lowers it.
- Calculations in series circuits; the total of two resistors in parallel is not calculated.
- \(R_{\mathrm{total}} = R_1 + R_2\) (not on the sheet)
6.2.3Domestic uses and safety
- Direct and alternating p.d.; UK mains is ac at 50 Hz and about 230 V.
- Three-core cable: live (brown), neutral (blue), earth (green and yellow).
- Why a live wire is dangerous even with the switch open, and why any connection between live and earth is dangerous.
6.2.4Energy transfers
- Power of a device from p.d. and current, or from current and resistance.
- Energy transferred depends on power and time switched on; appliances transfer energy to motors and heaters.
- The National Grid: step-up transformers for transmission, step-down for homes, and why this is efficient. How a transformer is built is not needed.
- HT Use the transformer power equation from the equations sheet.
- \(P = VI\)
- \(P = I^2R\)
- \(E = Pt\)
- \(E = QV\)
- \(V_{\mathrm{p}}I_{\mathrm{p}} = V_{\mathrm{s}}I_{\mathrm{s}}\) HT
6.3Particle model of matter
Physics Paper 1 · topic 20
6.3.1Changes of state and density
- Particle diagrams of solids, liquids and gases, and how they explain differences in density.
- Melting, freezing, boiling, evaporating, condensing and subliming conserve mass; they are physical changes, reversed to get the original material back.
Required practical 17 · density
6.3.2Internal energy and energy transfers
- Internal energy is the total kinetic and potential energy of all the particles.
- Heating raises the temperature or changes the state.
- Specific latent heat of fusion and of vaporisation: energy for a change of state with no change in temperature.
- Heating and cooling graphs; telling specific heat capacity and latent heat apart.
- \(\Delta E = mc\Delta\theta\)
- \(E = mL\)
6.3.3Particle model and pressure
- Gas molecules move randomly; temperature relates to their average kinetic energy.
- At constant volume, a hotter gas exerts a higher pressure.
6.4Atomic structure
Physics Paper 1 · topic 21
6.4.1Atoms and isotopes
- Atom radius about \(1 \times 10^{-10}\) m; nucleus under \(\dfrac{1}{10\,000}\) of that but holding almost all the mass.
- Electrons in energy levels move up by absorbing and down by emitting electromagnetic radiation.
- Atomic number, mass number, isotopes and positive ions.
- How the model changed: solid spheres, plum pudding, the nuclear model from alpha scattering, Bohr’s orbits, protons, Chadwick’s neutron.
6.4.2Atoms and nuclear radiation
- Unstable nuclei decay at random; activity in becquerels; count rate.
- Alpha, beta, gamma and neutron emission; penetration, range in air and ionising power, and choosing a source for a job.
- Balanced nuclear equations for single alpha and beta decays.
- Half-life, found from data or a graph. HT The fraction left after a number of half-lives, as a ratio.
- Contamination against irradiation; why studies of radiation effects are published for peer review.
6.5Forces
Physics Paper 2 · topic 22
6.5.1Forces and their interactions
- Scalars and vectors; forces as arrows.
- Contact forces (friction, air resistance, tension, normal contact) and non-contact forces (gravitational, electrostatic, magnetic).
- Weight, centre of mass, and weight in proportion to mass.
- The resultant of forces along a line.
- HT Free body diagrams; resolving a force into two components; scale vector diagrams for resultants and equilibrium.
6.5.2Work done and energy transfer
- A force does work when it moves an object; 1 J = 1 N m.
- Work against friction raises the temperature.
6.5.3Forces and elasticity
- Stretching, bending and compressing need more than one force; elastic against inelastic deformation.
- Extension is proportional to force up to the limit of proportionality; linear and non-linear graphs.
- Work done on a spring is stored as elastic potential energy.
- \(F = ke\)
- \(E_{\mathrm{e}} = \tfrac{1}{2}ke^2\)
Required practical 18 · force and extension
6.5.4.1Describing motion
- Distance and displacement, speed and velocity; typical speeds (walk 1.5, run 3, cycle 6, sound 330 m/s).
- Speed from the gradient of a distance–time graph; acceleration from the gradient of a velocity–time graph.
- HT Circular motion has constant speed but changing velocity; tangents to curved distance–time graphs; distance from the area under a velocity–time graph.
- Free fall at about 9.8 m/s²; an object falling through a fluid reaches terminal velocity.
- \(s = vt\)
- \(a = \dfrac{\Delta v}{t}\)
- \(v^2 - u^2 = 2as\)
6.5.4.2Newton’s laws
- First law: velocity changes only if there is a resultant force. HT Inertia.
- Second law: acceleration is proportional to resultant force and inversely proportional to mass. HT Inertial mass as \(\dfrac{\text{force}}{\text{acceleration}}\).
- Estimating speeds, accelerations and forces for road vehicles.
- Third law: interacting objects exert equal and opposite forces.
Required practical 19 · force, mass and acceleration
6.5.4.3Forces and braking
- \(\text{stopping distance} = \text{thinking distance} + \text{braking distance}\); faster means further for a given braking force.
- Reaction times of 0.2 to 0.9 s, lengthened by tiredness, drugs, alcohol and distractions; measuring them.
- Road, weather, brakes and tyres affect braking distance; brakes do work that heats them; dangers of large decelerations.
- Estimate how emergency stopping distance changes over typical speeds.
- HT Estimate braking forces for road vehicles.
6.5.5Momentum HT
- Momentum as mass × velocity.
- Momentum is conserved in a closed system; describe and explain examples such as collisions.
6.6Waves
Physics Paper 2 · topic 23
6.6.1Waves in air, fluids and solids
- Transverse and longitudinal waves (compressions and rarefactions); the wave moves, not the medium.
- Amplitude, wavelength, frequency and period; measuring the speed of sound and of ripples.
- \(T = \dfrac{1}{f}\)
- \(v = f\lambda\)
Required practical 20 · waves in a ripple tank and a solid
6.6.2Electromagnetic waves
- The spectrum from radio to gamma; all at the same speed in a vacuum; transverse waves that transfer energy.
- Ray diagrams for refraction. HT Wavefront diagrams; absorption, transmission, refraction and reflection depending on wavelength.
- HT Radio waves made by, and inducing, oscillations in circuits.
- Hazards of ultraviolet, X-rays and gamma rays; dose in sieverts.
- Uses of each type. HT Why each type suits its use.
Required practical 21 · infrared from different surfaces
6.7Magnetism and electromagnetism
Physics Paper 2 · topic 24
6.7.1Magnets and magnetic fields
- Poles; like poles repel, unlike attract; permanent and induced magnets.
- Field lines run north to south and are densest at the poles; plotting them with a compass.
- The Earth’s magnetic field as evidence of a magnetic core.
6.7.2The motor effect
- The field around a wire and a solenoid; an iron core makes an electromagnet.
- HT Fleming’s left-hand rule; the force on a wire; how a coil turns in a motor.
