IGCSE›Oxford AQA IGCSE Physics›Mind mapsElectrical CircuitsOxford AQA IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsCharge flowMetals have free electrons that driftCurrent is rate of flow of chargeI=QtI = \frac{Q}{t}I=tQPotential difference is energy per unit chargeV=EQV = \frac{E}{Q}V=QEStatic electricityFriction transfers electrons between insulatorsCharge stays put until a dischargeLightning is a large-scale dischargeResistanceV=IRV = IRV=IRGreater resistance means smaller currentCharges collide with atoms, causing heatingResistor at constant temperature obeys Ohm's LawCircuitscurrent and resistanceIIIVVVRRRQQQI-V graphsResistor: straight line through the originFilament lamp: resistance rises with temperatureDiode: conducts in forward direction onlyThermistor resistance falls as temperature risesLDR resistance falls as light risesSeries and parallelSeries: same current, resistances addSeries: pd is shared between componentsParallel: same pd across each branchParallel: combined resistance is lower than smallestParallel branches work independentlyExam tipsAlways quote unitsA filament lamp does not obey Ohm's LawKnow the I-V practical and control variables