H2 Physics 9478 · Topic 13
Current electricity: charge flow, energy and a.c.
Connect microscopic charge transport to circuit energy and power, then distinguish instantaneous, peak and r.m.s. a.c. quantities before analysing resistive power and a single diode.
Before you begin
Study each reviewed objective cluster, then use the recorded diagnostic and repair plan. H2 practice evidence remains separate from H1 and H3.
Be comfortable with: Quantities & Measurement objective chainOscillations objective chain
How the ideas connect
- Charge flow, current and drift velocity
- Potential difference, power and e.m.f.
- Sinusoidal a.c., peak and r.m.s. values
- Mean a.c. power and half-wave rectification
Learn in order
Lesson route
Objective clusters
- 01Charge flow, current and drift velocity 15(a)–(b)Learn and apply 2 reviewed syllabus outcomes in one coherent cluster.
- 02Potential difference, power and e.m.f. 15(c)–(e)Learn and apply 3 reviewed syllabus outcomes in one coherent cluster.
- 03Sinusoidal a.c., peak and r.m.s. values 15(f)–(g), 15(i)Learn and apply 3 reviewed syllabus outcomes in one coherent cluster.
- 04Mean a.c. power and half-wave rectification 15(h), 15(j)Learn and apply 2 reviewed syllabus outcomes in one coherent cluster.
Prove your understanding
Practice and repair
Key ideas and reference
Use this concise Current electricity: charge flow, energy and a.c. checklist to locate the right objective cluster. Full definitions, derivations and worked examples stay in the linked lessons.
- Connect microscopic charge transport to circuit energy and power, then distinguish instantaneous, peak and r.m.s. a.c. quantities before analysing resistive power and a single diode.
- Charge flow, current and drift velocity 15(a)–(b)
- Potential difference, power and e.m.f. 15(c)–(e)
- Sinusoidal a.c., peak and r.m.s. values 15(f)–(g), 15(i)
- Mean a.c. power and half-wave rectification 15(h), 15(j)
Course coverage and review details
Topic 15 states no explicit exclusions. q in I = nAvq is treated as carrier-charge magnitude when calculating current magnitude; electron drift is opposite conventional current. E.m.f. is energy supplied per unit charge, while p.d. is energy transferred from electrical form per unit charge. The peak/√2 and half-maximum-power results are restricted to sinusoidal waveforms and a resistive load; a single ideal diode gives unsmoothed half-wave rectification.
Coverage is reviewed against 9478 topic 15(a)–(j), PDF page 24. Selected-response progress does not by itself prove constructed, diagrammatic or practical performance.
Reviewed 2026-08-01