H1 Physics 8867 · Nov 2023PhysicsPaper 1Most challenging

Paper 1 Q21 — Terminal p.d. and lost volts

D.C. circuits — e.m.f., internal resistance and terminal p.d.

What the examiners said

“Those candidates who got this wrong mostly chose option A.” The report gives no further detail for Q21, but its general comments flag circuit questions as an area candidates found challenging — this reconstruction targets the classic circuits trap of ignoring internal resistance.

Try the question (reconstruction)

A battery of e.m.f. 6.0 V and internal resistance 0.50 Ω is connected to a 2.5 Ω resistor. What is the potential difference across the battery terminals?

Examiner report: “Wrong answers clustered on one distractor — consistent with reaching for the ‘obvious’ unadjusted value.”

Explore — where do the volts go?

Vary the load. The stacked bar splits the e.m.f. into terminal p.d. (useful) and lost volts (heating the battery). Watch what happens as R shrinks.

Load R (Ω): 2.5 Internal r (Ω): 0.5

Push R towards 0 (short circuit): the terminal p.d. collapses and nearly all 6 V is ‘lost’ inside the battery. Open-circuit it (large R) and V → ε.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H1 Physics 8867 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org