Playbook
Electrostatics
166 q - 3.83/paper - 22% HARD. The heaviest chapter on the Physics paper. Gauss's law and the dipole are 29 questions without a HARD one; dielectrics are 39% HARD.
- Questions in the bank
- 166
- q/paper (2024–25 papers)
- 3.83
- Tagged HARD
- 22%
- Subtopics
- 7
Strand: Cornerstone
When you’ll see it
Charges, a field or a potential, a capacitor with or without a slab between its plates, or a closed surface and the flux through it.
How this chapter is tested
166 q at 3.83 a paper makes this the heaviest chapter on the Physics paper — close to four marks every sitting. It is 22% HARD, but the HARD is not everywhere. Gauss's Law and Electric Flux (20 q) and the Electric Dipole page (9 q) have never produced a HARD question between them. Dielectrics in Capacitors (23 q, 39%) and Coulomb's Law and Electric Field (27 q, 30%) carry most of it.
The biggest page is Electric Potential and Potential Energy, 43 questions at 21%. Potential is a scalar, which is the whole reason it is easier than field: add the potentials of several charges as plain numbers, with their signs. Field questions need vector addition, and that is where the Coulomb page gets expensive.
The capacitor half of the chapter (67 questions over three pages) turns on one question each time: what is held constant? A capacitor still connected to the battery keeps its V; one disconnected keeps its Q. Every change in C — a slab inserted, plates moved apart — then moves Q, V and the energy in opposite directions in the two cases.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Flux and Gauss's law
Flux through a closed surface is q_enclosed/ε₀, whatever its shape; a charge at the centre of a cube sends a sixth of that through each face. 20 questions and no HARD one.
Potential and potential energy
V = kq/r, added as scalars with signs. Work to move a charge = q(V_B − V_A); on an equipotential surface it is zero.
Capacitors in combination
Parallel add; series add as reciprocals. C = ε₀A/d, and a dielectric of constant K multiplies it by K.
Energy and the constant-Q / constant-V split
U = ½CV² = Q²/2C. Battery connected: V fixed, so a slab raises Q and U. Battery removed: Q fixed, so a slab lowers V and U.
Field of charges and the dipole
E = kq/r² as a vector; on the dipole axis E = 2kp/r³, on the equator kp/r³, and torque = pE sin θ.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Forgetting what is held constant
Inserting a slab into a charged, ISOLATED capacitor lowers its energy; into one still on the battery, it raises it. Both answers are printed. Decide Q-fixed or V-fixed before writing a formula.
Adding fields as scalars
Fields from two charges add as vectors — at the midpoint of two equal like charges they cancel. Potentials add as numbers and do not. Mixing the two rules gives an option every time.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Electrostatics notesDrill every electrostatics question
166 questions from the bank, scoped to 7 bundled subtopics.
Drill one subtopic at a time
The 7 subtopics this playbook covers, in catalog order.
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