LuduminaMG-09 · MG-U3 · Planned
Transformers and quantitative transmission
Learning objectives
Explain AC transformer action; calculate turns/p.d. ratios and ideal power/current changes; connect to Grid losses.
8463 §§4.7.3.4 / No Trilogy counterpart
DfE single-science pp.41–42 / Combined pp.34–35. Evidence checked 30 September–1 October 2026. Skills: WS1.4,3.6; MS1c,3b,3c.
Explanation
Alternating current in a primary coil changes the core field and induces secondary p.d. The turns ratio sets the p.d. ratio. Ideal power equality means stepping voltage up steps current down for the same transferred power; real losses must be stated separately.
Concepts, equations and units: Vp/Vs=np/ns; ideal VpIp=VsIs; V,A,W; alternating core field; actual efficiency separately stated.
Prediction, demonstration and game exercise
Predict, observe, explain
Show two coils on iron core; predict step-up/down voltages, distinguish ideal from measured power.
Planned learner game exercise
Choose turns and current ratings for a model distribution chain; compare cable loss at fixed transmitted power.
Independent practice
Three transformer/ideal-power problems plus a Grid explanation; use I²R from EL-08.
Original practice example · Separate Physics Higher
An ideal transformer has 100 primary turns and 500 secondary turns with 12 V input. Find output p.d.
Show working and model answer
Working / reasoning
Vp/Vs = np/ns; Vs = 12 × 500/100.
Answer
60 V.
Exit check and success criteria
Two calculations correct, step-up implies lower secondary current for ideal fixed power, and AC requirement explained.
During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.
Misconceptions, practical links and mastery
Check these misconceptions
Transformer works continuously on DC; more turns create power; ideal input/output equality asserted for real lossy device.
Practical preparation
Optional approved low-voltage transformer demonstration; no RP.
Virtual preparation and revision only. Required hands-on activities and school records remain separate.
Proposed mastery
0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.