PhysicsQ&A by dot point

Combining resistors in series and parallel, the application of Kirchhoff's two laws, the conservation of charge and energy in circuits, and power dissipation given by P = VI, P = I squared R and P = V squared over R.

Electric current as the rate of flow of charge, the equation Q = It, charge carriers and number density, the equation I = nAvq for current, and Kirchhoff's first law as conservation of charge.

The definition of potential difference and resistance, Ohm's law, the I-V characteristics of an ohmic conductor, a filament lamp and a diode, and how the resistance of a thermistor and LDR varies.

Electromotive force as energy per unit charge, internal resistance, the equations linking EMF, terminal potential difference and lost volts, and measuring EMF and internal resistance experimentally.

The potential divider as a way of producing a required potential difference, the divider equation, the use of variable resistors and potentiometers, and divider circuits using thermistors and LDRs as sensors.

Resistivity and the equation R = rho L / A, the effect of length and cross-sectional area on resistance, how resistivity varies with temperature for a metal, and superconductivity and its uses.

Sinusoidal alternating current and voltage, peak and root mean square values, the oscilloscope, the transformer equation, transformer efficiency and the transmission of electrical power.

The definition of capacitance, the energy stored on a capacitor, the effect of a dielectric and relative permittivity, and parallel plate capacitors.

Exponential charge and discharge of a capacitor through a resistor, the time constant, and graphical and logarithmic analysis of the decay.

Coulomb's law, electric field strength as force per unit charge, the radial field of a point charge, uniform fields between plates, and the motion of charged particles in uniform fields.

Absolute electric potential and potential energy in a radial field, the potential gradient, equipotentials, and the work done moving a charge.

Magnetic flux and flux linkage, Faraday's law and Lenz's law, the emf induced in a moving conductor, and the emf induced in a rotating coil.

The concept of a force field, Newton's law of gravitation, gravitational field strength as a vector, and the radial and uniform field models.

Gravitational potential and potential energy in a radial field, the potential gradient, equipotential surfaces, and the work done moving a mass between points.

Magnetic flux density, the force on a current-carrying conductor, the force on a moving charge, Fleming's left hand rule, and the circular motion of charged particles.

Orbital motion under gravity, the link to centripetal force, Kepler's third law, the energy of an orbiting body, and synchronous and geostationary orbits.

Motion in a circle at constant speed, angular speed, centripetal acceleration and the centripetal force that keeps an object on a circular path.

Free and forced vibrations, damping, resonance and the effect of damping on the sharpness of the resonance peak.

The gas laws, the ideal gas equation in molar and molecular forms, absolute zero and the experimental basis of the gas laws.

The molecular kinetic theory model, the assumptions behind it, the kinetic theory equation, root mean square speed, and the link between mean kinetic energy of a molecule and absolute temperature.

The defining condition for simple harmonic motion, the equations for displacement, velocity and acceleration, and the interchange between kinetic and potential energy in SHM systems such as the mass-spring and simple pendulum.

Internal energy, the distinction between temperature change and change of state, specific heat capacity and specific latent heat, and continuous flow and method of mixtures experiments.

Orders of magnitude, estimation of approximate values of physical quantities to the nearest power of ten, and using such estimates to check the plausibility of calculated results.

Random and systematic errors, precision and accuracy, repeatability and reproducibility, absolute, fractional and percentage uncertainty, and how uncertainties combine and are shown on graphs.

SI base units, units derived from them, the use of standard prefixes, and checking equations for homogeneity using base units.

Density, Hooke's law and the spring constant, elastic and plastic behaviour, tensile stress and strain, the energy stored in a stretched material, and the difference between brittle and ductile behaviour.

The principle of conservation of energy, interconversion of kinetic and gravitational potential energy, energy dissipated by resistive forces, and applying conservation of energy to falling and oscillating systems.

The moment of a force about a point, the principle of moments, couples and torque, the centre of mass, and the conditions for the equilibrium of a rigid body under coplanar forces.

Momentum as mass times velocity, the principle of conservation of momentum, force as rate of change of momentum, impulse and the area under a force-time graph, and elastic and inelastic collisions.

Definitions of displacement, speed, velocity and acceleration, interpreting motion graphs, the equations of uniformly accelerated motion (suvat), and motion under gravity.

Newton's three laws of motion, the equation F = ma for constant mass, the meaning of inertia and inertial mass, and applying the laws to connected bodies and everyday situations.

Independence of horizontal and vertical motion, applying the suvat equations to projectiles launched horizontally and at an angle, and the effect of air resistance on the trajectory.

Distinguishing scalars and vectors, adding vectors by calculation and scale drawing, resolving a vector into perpendicular components, and the conditions for equilibrium of coplanar forces.

The Young modulus as the ratio of tensile stress to tensile strain, the gradient of a stress-strain graph, the experiment to measure it for a wire, and interpreting stress-strain curves up to the breaking point.

Work done by a force including a force at an angle, the relationship between power, work and velocity, kinetic and gravitational potential energy, and efficiency as the ratio of useful output to total input.

The nature, penetration, ionising power and range of alpha, beta and gamma radiation, the inverse square law for gamma, background radiation and the uses and hazards of radiation.

Induced nuclear fission by thermal neutrons, the chain reaction, critical mass, and the factors controlling whether the reaction is sustained.

Mass and energy equivalence, mass defect and binding energy, the binding energy per nucleon curve, and the energy released in fission and fusion.

The relationship between the numbers of neutrons and protons in stable and unstable nuclei, the N against Z graph, and predicting the mode of decay including alpha, beta-minus, beta-plus and gamma emission.

Estimating nuclear radius from closest approach of alpha particles and from electron diffraction, the dependence of radius on nucleon number, and the constancy of nuclear density.

The function of the moderator, control rods and coolant in a thermal nuclear reactor, the safety features, and the handling and disposal of radioactive waste.

Radioactive decay as a random process, the decay constant, the activity of a source, the exponential decay law, half-life and applications such as radioactive dating.

The Rutherford alpha particle scattering experiment, the observations and conclusions, and how they led to the nuclear model of the atom.

Hadrons (baryons and mesons), leptons, the conservation of baryon number, lepton number, strangeness and charge, the properties of the kaon and pion, and the decay of particles.

Protons, neutrons and electrons, their relative charges and masses, proton number, nucleon number, isotopes and the use of the notation for representing nuclides, and specific charge.

Discrete energy levels in atoms, excitation and de-excitation, ionisation, the relationship between photon energy and energy level difference, line spectra, and the operation of the fluorescent tube.

The four fundamental interactions, the concept of exchange particles (gauge bosons), the W bosons, the photon and the pion, and the use of Feynman diagrams to represent interactions such as beta decay and electron-proton collisions.

Antiparticles and their properties, the photon model of electromagnetic radiation, the photon energy equation, and the processes of annihilation and pair production with their energy calculations.

The photoelectric effect, the threshold frequency and work function, the photoelectric equation, and how the effect provides evidence for the particle nature of electromagnetic radiation.

The properties of up, down and strange quarks and their antiquarks, the quark composition of baryons and mesons, the application of conservation laws to quark changes, and the quark model of beta decay.

The strong nuclear force and its range, the balance of forces in the nucleus, alpha, beta-minus and gamma radiation, and how the equation for beta-minus decay reveals the existence of the neutrino.

The evidence for the wave nature of light and the particle nature of light, the de Broglie wavelength of a particle, electron diffraction as evidence for the wave nature of matter, and the link between momentum and wavelength.

Diffraction of waves at a single slit, the appearance of the single-slit pattern with white light and monochromatic light, the diffraction grating, the grating equation, and its applications in spectra.

The principle of superposition, path difference and phase difference, constructive and destructive interference, the conditions of coherence, Young's double-slit experiment, and the double-slit fringe equation.

Progressive waves and the transfer of energy, amplitude, frequency, wavelength, period, speed and phase, the wave equation, and the difference between transverse and longitudinal waves including polarisation.

Refraction and the refractive index of a substance, Snell's law at a boundary, the critical angle, total internal reflection, and the operation of optical fibres.

The formation of stationary waves from two progressive waves travelling in opposite directions, nodes and antinodes, the differences between stationary and progressive waves, and resonance on strings and in air columns.