Capacitors: JAMB Physics Questions, Answers & Notes

What Capacitors covers in the JAMB Physics syllabus

A capacitor stores charge (and energy) between two plates separated by an insulating dielectric. Capacitance C = Q/V (unit farad), so charge Q = CV. Capacitance increases with larger plate area, smaller plate separation, and a dielectric between the plates. Capacitors in parallel add (C = C₁ + C₂ + …); in series they combine by 1/C = 1/C₁ + 1/C₂ (total less than the smallest). Energy stored W = ½QV = ½CV². Capacitors are used to store charge and smooth, tune, time and filter signals in electronic circuits.

For Capacitors, JAMB expects you to be able to:

• Define capacitance and apply C = Q/V
• Combine capacitors in series and parallel
• Calculate stored charge and energy and explain uses and the dielectric

Key facts & revision notes: Capacitors

These are the recurring points our Capacitors questions test — revise them until each feels automatic, then practise the questions above to lock them in.

• A capacitor stores electric charge (and energy in an electric field).
• Capacitance is measured in farads (F).
• Capacitance C = Q/V (charge stored per unit potential difference).
• The plates are separated by an insulating material called the dielectric.
• Capacitance increases with plate area (C ∝ A).
• Capacitance decreases as plate separation increases (C ∝ 1/d).
• From C = Q/V, the charge is Q = CV.
• Capacitors in parallel add: C_total = C₁ + C₂ + …
• In parallel, C = 2 + 3 = 5 F.
• In series, 1/C = 1/C₁ + 1/C₂ (the total is less than the smallest).
• 1/C = 1/6 + 1/6 = 2/6 = 1/3, so C = 3 F.
• Energy stored W = ½QV = ½CV².
• Charging stops when the capacitor's voltage equals the supply voltage.
• A dielectric increases the capacitance compared with a vacuum/air between the plates.
• Capacitors store charge and are used for smoothing, tuning, timing and filtering in circuits.
• W = ½CV² = ½ × 4 × 5² = ½ × 4 × 25 = 50 J.
• Capacitors resist rapid voltage changes, which smooths the output of a rectifier.
• Parallel connection adds capacitances, giving the largest total; series gives the smallest.
• Energy is stored in the field between the plates.
• In parallel, capacitances add: 4 + 6 = 10 F.
• Series capacitance is smaller than the smallest capacitor.
• 1/C = 1/4 + 1/4 = 1/2, so C = 2 F.
• W = ½ × 2 × 4² = ½ × 2 × 16 = 16 J.
• One plate is +Q and the other −Q.

Worked examples

Three Capacitors questions with the answer and a short explanation, so you can see how the topic is set before you practise the full set.

How Capacitors is tested in JAMB Physics

Our Capacitors bank holds 40 questions (2 easy, 28 medium, 10 hard). JAMB Physics typically returns to Capacitors year after year, so steady practice on this topic is high-value revision. Questions are multiple-choice with four options, and at UTME pace you get roughly 40 seconds each — which is why timed practice matters.

How to answer Capacitors questions

Work the stem first and predict the answer before you look at the options; then eliminate the ones that contradict the key facts above. Watch for “which is not…”, “all of the above” and “except” style stems, which are where rushed candidates lose easy marks on Capacitors. If a calculation or a precise definition is involved, work it from first principles rather than guessing from a half-remembered rule. When two options look right, re-read the stem for the qualifier that separates them — JAMB rarely repeats an option by accident. If you are still unsure, eliminate the two weakest choices to lift your odds, flag the question, and move on; never burn a full minute on one Physics item when the exam gives you about forty seconds each. Then come back to flagged questions with whatever time remains. The single most reliable way to get faster at Capacitors is repeated timed practice, so use the button above until the recurring patterns feel automatic.

Common mistakes to avoid in Capacitors

The errors that cost marks on Capacitors are usually careless rather than conceptual: misreading a negative stem, confusing two similar terms, or rushing a definition you actually know. Candidates also over-rely on “expo” and last-minute cramming instead of understanding the topic — which fails the moment JAMB rephrases a familiar idea. Treat every option as a claim to be checked against the facts above, keep your working tidy for any calculation, and don’t change a considered answer on a hunch. Above all, revise Capacitors actively by answering questions, not just by re-reading notes — recall under time is what the exam rewards.

Frequently asked questions

Is Capacitors part of the JAMB Physics syllabus?

Yes. Capacitors is a recognised topic in the JAMB Physics syllabus, covering define capacitance and apply C = Q/V. You should be able to recall its key facts and apply them to multiple-choice questions.

How many Capacitors questions can I practise on Belmadeng?

There are 40 original, JAMB-standard Capacitors questions in our free bank, each with the correct answer and a worked explanation. You can practise them untimed or as a timed test.

What are the most important points to know about Capacitors?

A capacitor stores charge (and energy) between two plates separated by an insulating dielectric. Capacitance C = Q/V (unit farad), so charge Q = CV. Capacitance increases with larger plate area, smaller plate separation, and a dielectric between the plates. Capacitors in parallel add (C = C₁ + C₂ + …

How do I answer Capacitors questions quickly in JAMB?

Read the stem carefully, eliminate clearly wrong options, and match the remaining choices to the key facts for Capacitors. Practising timed Capacitors questions builds the speed you need for UTME's pace of about 40 seconds per question.

Are these JAMB Physics Capacitors questions past questions or original?

They are original questions written to JAMB (UTME) standard and mapped to the official syllabus — not reproduced past papers. This keeps them legal to use freely while closely mirroring how the real exam tests the topic.

Where can I practise Capacitors questions free without signing up?

Right here — tap “Start Capacitors practice” on this page to begin instantly. Belmadeng's CBT practice is completely free and needs no sign-up, download or subscription.

About these questions: original, JAMB-standard items written from the official UTME Physics syllabus (last reviewed 2026-09-18). Belmadeng is an independent study platform and is not affiliated with JAMB. Spotted an error? Use the report link.