IB›IB Physics HL›Mind mapsD.2 Electric and magnetic fieldsIB Physics HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsChargeCoulomb: F=kq1q2r2F = \frac{kq_1q_2}{r^2}F=r2kq1q2Charge is conserved in an isolated systemMillikan: charge quantised in units of ee=1.60×10−19 Ce = 1.60 \times 10^{-19}\,\text{C}e=1.60×10−19CChargingFriction: electrons move between insulatorsContact: same sign of chargeInduction: rod separates charge, then earthRemove earth before removing the rodLeaves charge opposite to the rodField strengthE=FqE = \frac{F}{q}E=qF, force per unit positive chargeField lines: positive to negativeLine density shows strengthParallel plates: uniform, E=VdE = \frac{V}{d}E=dVMagnetic field lines are closed loopsElectric fieldsand magnetic fieldsEEEVeV_eVekkkEnergy, potentialEp=kq1q2rE_p = \frac{kq_1q_2}{r}Ep=rkq1q2: positive for like chargesUnlike charges: EpE_pEp negativeVe=kQrV_e = \frac{kQ}{r}Ve=rkQ, work per unit charge from infinityPotential is a scalar; work W=qΔVeW = q\Delta V_eW=qΔVeGradientE=−ΔVeΔrE = -\frac{\Delta V_e}{\Delta r}E=−ΔrΔVeField points to decreasing potentialEquipotentials perpendicular to field linesClose together where field is strongPlates: V changes linearly, E constantExam tipsField strengths add as vectorsPotentials add as ordinary numbersMidpoint of equal charges: E = 0, V is not