Edexcel International AS & A Level Physics: every topic, by paper

Name the six SI base quantities used at A-Level and their units.

Mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol).

Express the newton in SI base units.

kg m s⁻².

Express the joule in SI base units.

kg m² s⁻².

Define displacement.

Distance moved in a specified direction.

Define acceleration.

Rate of change of velocity.

What does the gradient of a displacement–time graph show?

Velocity.

State Newton's first law.

An object stays at rest or moves with constant velocity unless a resultant force acts on it.

State Newton's second law in terms of momentum.

Resultant force is proportional to the rate of change of momentum: F = Δp ÷ Δt.

State Newton's third law.

If body A exerts a force on body B, B exerts an equal and opposite force of the same type on A.

Define the moment of a force.

Force × perpendicular distance from the pivot to the line of action of the force.

State the principle of moments.

For equilibrium, the sum of clockwise moments about a point equals the sum of anticlockwise moments.

What are the two conditions for equilibrium?

No resultant force and no resultant moment (torque).

Define work done.

Force × displacement in the direction of the force.

Define power.

Rate of doing work (or transferring energy): P = W ÷ t.

Give the formula for kinetic energy.

Ek = ½mv².

State Hooke's law.

Extension is proportional to force, up to the limit of proportionality: F = kx.

Define stress.

Force per unit cross-sectional area: σ = F ÷ A (Pa).

Define strain.

Extension per unit original length: ε = x ÷ L (no units).

Distinguish transverse and longitudinal waves.

Transverse: oscillations perpendicular to the direction of energy transfer. Longitudinal: oscillations parallel to it.

Define wavelength, amplitude and frequency.

Wavelength: distance between adjacent points in phase. Amplitude: maximum displacement from equilibrium. Frequency: oscillations per second.

Give the wave equation.

v = fλ.

State the principle of superposition.

When waves meet, the resultant displacement is the vector sum of the individual displacements.

What is diffraction?

Spreading of a wave through a gap or around an obstacle; greatest when the gap is similar to the wavelength.

What conditions are needed for observable interference?

Coherent sources (constant phase difference) with similar amplitudes.

Define electric current.

Rate of flow of charge: I = ΔQ ÷ Δt.

Define potential difference.

Energy transferred per unit charge from electrical to other forms: V = W ÷ Q.

Define the coulomb.

The charge passing a point when a current of 1 A flows for 1 s.

Define electromotive force (e.m.f.).

Energy transferred from other forms to electrical energy per unit charge by a source.

What is internal resistance?

Resistance within a source, causing lost volts when current flows.

Give the equation linking e.m.f., terminal p.d. and internal resistance.

ε = V + Ir = I(R + r).

What is a photon?

A discrete packet (quantum) of electromagnetic energy.

Give the energy of a photon.

E = hf = hc ÷ λ.

Define the electronvolt.

The energy gained by an electron accelerated through 1 V: 1.6 × 10⁻¹⁹ J.

State Newton's first law.

An object stays at rest or moves with constant velocity unless a resultant force acts on it.

State Newton's second law in terms of momentum.

Resultant force is proportional to the rate of change of momentum: F = Δp ÷ Δt.

State Newton's third law.

If body A exerts a force on body B, B exerts an equal and opposite force of the same type on A.

Define the radian.

The angle subtended at the centre of a circle by an arc equal in length to the radius.

Define angular velocity.

Rate of change of angle: ω = Δθ ÷ Δt = 2π ÷ T.

How is linear speed related to angular velocity?

v = ωr.

Define electric field strength.

Force per unit positive charge: E = F ÷ Q (N C⁻¹).

What is the field strength between parallel plates?

Uniform: E = V ÷ d.

State Coulomb's law.

F = Qq ÷ 4πε₀r².

Define capacitance.

Charge stored per unit potential difference: C = Q ÷ V.

What is the unit of capacitance?

The farad (F), one coulomb per volt.

How are capacitors combined in parallel and series?

Parallel: C = C₁ + C₂. Series: 1 ÷ C = 1 ÷ C₁ + 1 ÷ C₂.

What is a magnetic field?

A region where a magnet, magnetic material or current-carrying conductor experiences a force.

Give the force on a current-carrying wire in a magnetic field.

F = BIL sin θ.

Define the tesla.

The flux density giving a force of 1 N on a 1 m wire carrying 1 A at right angles to the field.

Define magnetic flux.

Φ = BA, the product of flux density and the area perpendicular to the field.

Define magnetic flux linkage.

NΦ, flux × number of turns.

State Faraday's law.

The induced e.m.f. is proportional to the rate of change of flux linkage.

What did the alpha-particle scattering experiment show?

Most of the atom is empty space, with a tiny, dense, positively charged nucleus.

What is the nucleon number and proton number?

Nucleon number (A): protons + neutrons. Proton number (Z): protons.

What are hadrons, baryons and mesons?

Hadrons are made of quarks; baryons have three quarks; mesons have a quark and an antiquark.

What is thermal equilibrium?

No net transfer of thermal energy between objects because they are at the same temperature.

Convert 27 °C to kelvin.

300 K.

What is absolute zero?

0 K (−273.15 °C), the temperature at which a substance has minimum internal energy.

Name the three main types of radiation and their nature.

Alpha: helium nucleus. Beta: fast electron (or positron). Gamma: high-energy electromagnetic radiation.

Compare the ionising power and penetration of α, β and γ.

Alpha: most ionising, stopped by paper. Beta: moderate, stopped by a few mm of aluminium. Gamma: least ionising, reduced by thick lead.

Why is radioactive decay random and spontaneous?

It is impossible to predict which nucleus will decay next, and decay is unaffected by external conditions.

What is simple harmonic motion?

Motion where acceleration is proportional to displacement from a fixed point and directed towards it: a = −ω²x.

Give displacement as a function of time in SHM, starting from maximum displacement.

x = x₀ cos ωt.

What is the angular frequency of an oscillation?

ω = 2πf = 2π ÷ T.

Define gravitational field strength.

Force per unit mass: g = F ÷ m (N kg⁻¹).

State Newton's law of gravitation.

The force between two point masses is proportional to the product of their masses and inversely proportional to the square of their separation: F = GMm ÷ r².

Give g at distance r from a point mass M.

g = GM ÷ r².

Define luminosity.

The total power output of a star.

Define radiant flux intensity.

Power received per unit area: F = L ÷ 4πd².

What is a standard candle?

An object of known luminosity, used to find distances.