A-Level Physics: Quantities & Their Prepositions
Several students have asked me about the correct prepositions in written questions, particularly in electricity topics. As there I couldn't find a comprehensive list online, I thought I'd write and post this one.
This isn't just a case of getting the right words to guarantee more marks. The preposition usually encodes the physics. Current flows through a component (it is a flow); p.d. is across it (it is a difference between two points).
Getting the preposition right is getting the concept right. I.e. using the correct preposition helps you to picture what is happening in the physical model you are using which may well help you with the rest of the question.
Electricity
| Current |
THROUGH a component / wire |
| Potential difference (voltage) |
ACROSS a component |
| EMF |
OF a cell / source |
| Charge |
THROUGH a point · ON a plate / sphere |
| Resistance |
OF a component |
| Power |
dissipated IN / BY a resistor · delivered TO a device |
| Electric field strength |
AT a point |
Forces & mechanics
| Force |
ON an object · BETWEEN two objects |
| Weight |
OF an object |
| Tension |
IN a string / wire |
| Friction / drag / upthrust |
ON an object |
| Reaction force |
ON an object, FROM a surface |
| Speed / velocity / acceleration / momentum |
OF an object |
| Displacement |
OF an object, FROM a point |
| Moment (torque) |
ABOUT a pivot / axis |
Energy, work & power
| Work |
done ON an object, BY a force |
| Kinetic / potential energy |
OF an object |
| Energy |
transferred TO / FROM a system |
| Power |
OF an engine |
| Efficiency |
OF a machine / system |
Materials
| Stress / strain |
IN a material or wire |
| Tension / compression |
IN a rod or wire |
| Extension |
OF a spring / wire |
| Young modulus |
OF a material |
Fields (gravitational / electric / magnetic)
| Field strength |
AT a point |
| Gravitational / electric potential |
AT a point |
| Force |
ON a mass or charge, IN a field |
| Magnetic flux |
THROUGH a coil / area |
| Flux linkage |
THROUGH a coil |
| EMF |
induced IN a coil |
| Force |
ON a current-carrying conductor |
Waves
| Wavelength / frequency / amplitude |
OF a wave |
| Speed |
OF a wave (travelling THROUGH a medium) |
| Phase difference |
BETWEEN two points or waves |
| Path difference |
BETWEEN two waves |
| Intensity |
OF radiation, AT a point |
Circular motion & SHM
| Angular velocity / period |
OF an object |
| Centripetal / restoring force |
ON an object, directed TOWARDS the centre |
Thermal physics
| Temperature / internal energy |
OF a gas or system |
| Heat (thermal energy) |
transferred TO / FROM a body |
| Pressure |
OF a gas · ON a surface · exerted BY a gas |
| Specific heat capacity / latent heat |
OF a substance |
Quantum & nuclear
| Energy |
OF a photon |
| Work function / threshold frequency |
OF a metal |
| Kinetic energy |
OF a photoelectron |
| de Broglie wavelength |
OF a particle |
| Energy level |
OF an atom · energy difference BETWEEN levels |
| Photon |
emitted / absorbed BY an atom |
| Activity / decay constant / half-life |
OF a source or isotope |
| Binding energy |
OF a nucleus · PER nucleon |
Watch out for — common student errors
- “voltage through a resistor” → should be p.d. ACROSS it
- “current across a component” → should be current THROUGH it
- “work done to an object” → should be work done ON it (BY a force)
Thomas McKennan Tutors · A-Level Physics revision resource