Electric potential
Cambridge A-Level Physics (9702) · Unit 18: Electric fields · 7 flashcards
Electric potential is topic 18.5 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 18 — Electric fields , alongside Electric fields and field lines, Uniform electric fields and Electric force between point charges. In one line: Electric potential at a point is the work done per unit positive charge in bringing a small test charge from infinity to that point. It is a scalar quantity, measured in volts (V).
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 7 flashcards — 1 definition, 4 key concepts and 2 calculations — covering the precise wording mark schemes reward. Use the definition card to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Electric potential at a point
Electric potential at a point is the work done per unit positive charge in bringing a small test charge from infinity to that point. It is a scalar quantity, measured in volts (V).
What the Cambridge 9702 syllabus says
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- define electric potential at a point as the work done per unit positive charge in bringing a small test charge from infinity to the point
- recall and use the fact that the electric field at a point is equal to the negative of potential gradient at that point
- use V = Q / (4πε0r) for the electric potential in the field due to a point charge
- understand how the concept of electric potential leads to the electric potential energy of two point charges and use EP = Qq / (4πε0 r)
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9702 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in Electric potential
- › Divide the total charge by 1.6 x 10^-19 to express the charge value in terms of e.
- › Draw separate vector arrows for the force from each charge and then determine the resultant direction using the parallelogram of forces.
- › Always double-check the syllabus formulae for point charges: Force is (Q₁Q₂)/(4πε₀r²) whereas Field Strength is Q/(4πε₀r²).
- › Apply the rule that a negative charge experiences a force in the opposite direction to the electric field to balance gravitational weight acting downwards.
- › Draw and describe field lines for a point charge or isolated sphere as radial lines that appear to originate from the center.
Define electric potential at a point.
Electric potential at a point is the work done per unit positive charge in bringing a small test charge from infinity to that point. It is a scalar quantity, measured in volts (V).
What is the relationship between electric field strength and electric potential gradient?
The electric field at a point is equal to the negative of the potential gradient at that point. Mathematically, E = -dV/dr, where E is electric field strength and dV/dr is the potential gradient.
State the formula for the electric potential due to a point charge Q at a distance r.
The electric potential (V) is given by V = Q / (4πε₀r), where Q is the charge, r is the distance from the charge, and ε₀ is the permittivity of free space.
Explain how the concept of electric potential leads to electric potential energy.
Electric potential defines the potential energy per unit charge at a location. Multiplying the electric potential (V) at a point by the charge (q) placed at that point gives the electric potential energy (EP): EP = qV.
State the formula for the electric potential energy of two point charges, Q and q, separated by a distance r.
The electric potential energy (EP) is given by EP = Qq / (4πε₀r), where Q and q are the charges, r is the distance between them, and ε₀ is the permittivity of free space.
Describe the sign convention for electric potential energy.
If the charges are of the same sign (both positive or both negative), the electric potential energy is positive, representing repulsive forces. If the charges are of opposite signs, the electric potential energy is negative, representing attractive forces.
How does electric potential change as you move closer to a positive charge?
Electric potential increases as you move closer to a positive charge. This is because work must be done by an external force to bring a positive test charge closer to another positive charge against the repulsive electric field.
Review the material
Read full revision notes on Electric potential — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 18 — Electric fields
Electric potential sits alongside these A-Level Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Electric potential deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
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