Electric fields and field lines
Cambridge A-Level Physics (9702) · Unit 18: Electric fields · 7 flashcards
Electric fields and field lines is topic 18.1 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 18 — Electric fields , alongside Uniform electric fields, Electric force between point charges and Electric field of a point charge. In one line: An electric field is a region around a charged particle or object within which a force would be exerted on other charged particles or objects. Quantitatively, it is the force per unit positive charge.
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.
An electric field
An electric field is a region around a charged particle or object within which a force would be exerted on other charged particles or objects. Quantitatively, it is the force per unit positive charge.
What the Cambridge 9702 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Understand electric fields as one type of field of force; define electric field as the force exerted per unit positive charge.
- Recall and apply F = qE to find the force a charge experiences when placed in an electric field.
- Use field lines to represent an electric field.
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 fields and field lines
- › Draw and describe field lines for a point charge or isolated sphere as radial lines that appear to originate from the center.
- › Remember that the force on a negative charge like an electron is always in the opposite direction to the electric field lines.
- › Define electric field lines as indicating the direction of the force acting on a stationary positive charge.
Define an electric field.
An electric field is a region around a charged particle or object within which a force would be exerted on other charged particles or objects. Quantitatively, it is the force per unit positive charge.
What is the equation that relates force (F), charge (q), and electric field (E)?
The force (F) experienced by a charge (q) in an electric field (E) is given by the equation F = qE. This equation shows the force is proportional to both the charge and the electric field strength.
How are electric field lines used to represent an electric field?
Electric field lines show the direction and relative strength of the electric field. The direction of the field line indicates the direction of the force on a positive test charge. The closer the lines, the stronger the field.
Describe the electric field lines around a single positive point charge.
The electric field lines radiate outwards from the positive charge in all directions. They are straight lines, and their density decreases with increasing distance from the charge, indicating a weaker field.
Describe the electric field lines between two oppositely charged parallel plates.
The electric field lines are parallel and equally spaced, running from the positive plate to the negative plate. This indicates a uniform electric field between the plates, except near the edges.
What does the spacing of electric field lines indicate about the electric field strength?
The closer the electric field lines are to each other, the stronger the electric field is in that region. Conversely, the farther apart the lines are, the weaker the field.
A charge of +2.0 x 10⁻⁶ C experiences a force of 0.04 N in an electric field. What is the magnitude of the electric field?
Using F = qE, the electric field E = F/q = 0.04 N / 2.0 x 10⁻⁶ C = 2.0 x 10⁴ N/C. The electric field strength is 2.0 x 10⁴ Newtons per Coulomb.
Review the material
Read full revision notes on Electric fields and field lines — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 18 — Electric fields
Electric fields and field lines 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 fields and field lines 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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