IGCSE›Edexcel IGCSE Physics›Mind mapsCurrent, Potential Difference & ResistanceEdexcel IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsCurrentRate of flow of chargeIn metals: a flow of electronsQ=I×tQ = I \times tQ=I×t2 A for 30 s moves 60 CVoltageEnergy transferred per unit charge1 V=1 J/C1\,\text{V} = 1\,\text{J/C}1V=1J/CE=Q×VE = Q \times VE=Q×V10 C across 5 V transfers 50 JResistanceOpposes the flow of currentV=I×RV = I \times RV=I×RHigher resistance: less currentRearrange: I=VRI = \frac{V}{R}I=RV, R=VIR = \frac{V}{I}R=IVCurrent & p.d.and resistanceACVΩJCircuit rulesCurrent is conserved at a junctionParallel: same voltage across eachSeries: same current, voltage is sharedSeries resistances add upWorked exampleTwo 4 Ω resistors in series, 12 V supplyTotal resistance 8 ΩI=128=1.5 AI = \frac{12}{8} = \mathbf{1.5}\,\text{A}I=812=1.5AEach resistor gets 6 VExam tipsRearrange V=IRV = IRV=IR carefullyKnow every unit: A, C, J, Ω, s, V, WMarks for rearranging as well as the answer