IB›IB Physics SL›Mind mapsD.2 Electric and magnetic fieldsIB Physics SL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsChargeLike charges repel, unlike attractTotal charge of isolated system is conservedCharge is quantised: e=1.60×10−19 Ce = 1.60 \times 10^{-19}\,\text{C}e=1.60×10−19CMillikan: drop held still, q=mg/Eq = mg/Eq=mg/ECoulomb's lawF=kq1q2r2F = \frac{kq_1q_2}{r^2}F=r2kq1q2 for point chargesk=8.99×109 N m2C−2k = 8.99 \times 10^{9}\,\text{N m}^2\text{C}^{-2}k=8.99×109N m2C−2An inverse-square lawAlong the line joining the chargesChargingFriction: electrons transfer, equal opposite chargesContact: conductor gets the same signInduction: earth, remove earth, then rodInduction gives opposite sign to the rodOnly electrons move in metalsFieldselectric and magneticEEEBBBCTElectric fieldE=F/qE = F/qE=F/q, force per unit positive chargeLines start on +, end on −Parallel plates: uniform, E=V/dE = V/dE=V/dCloser lines mean stronger fieldMagnetic fieldLines leave N, enter S outside a magnetAlways closed loops, no monopolesStraight wire: circular lines around itSolenoid: uniform field insideExam tipsConvert nC and μC, then square rPositive charge does not flow: lose electronsHeld-up drop under a + top plate is negative