IGCSE›Edexcel IGCSE Physics›Mind mapsElectromagnetic InductionEdexcel IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsInductionVoltage induced by a changing magnetic fieldConductor moves through a fieldOr field through a coil changesBigger with faster, stronger, more turnsGeneratorsRotate a magnet in a coilOr a coil in a magnetic fieldDirection keeps reversing → a.c.Bicycle dynamo: pedal faster, brighter lampTransformersPrimary and secondary coils on an iron coreChanging field in core induces voltage in secondaryWork with a.c. onlyStep-up: more turns on secondaryStep-down: fewer turns on secondaryInductiongenerators, transformersVNpN_pNpNsN_sNsEquationsVpVs=NpNs\frac{V_p}{V_s} = \frac{N_p}{N_s}VsVp=NsNp100% efficient: VpIp=VsIsV_pI_p = V_sI_sVpIp=VsIs100 to 500 turns, 230 V → 1150 VNational GridStep-up for transmission: high V, low ILow current means less heating in cablesStep-down for safe domestic useExam tipsGive two factors affecting induced voltageTransformers do not work with d.c.Heating loss depends on current, not voltage