Remember: Electric fieldcaused by a capacitor(电容器-Q+Qd04REinside60+There is also a smallfield outside the plates:+(Q/ A) (aL+ing(R250
d Remember: Electric field caused by a capacitor (电容器 ) ( ) 0 inside Q A E There is also a small field outside the plates: ( ) R Q A d E 0 fringe 2 R - - - - - - - + + + + + + + -Q +Q
(Q/ A)What is the potential differenceEinsideacross the capacitor?60d+Q-Q+++++EEE+(Q / A)WhyisthereaAV=-Ed=minussign????%
- - - - - - - + + + + + + + E E What is the potential difference across the capacitor? ( ) 0 inside Q A E ( ) d Q A V Ed 0 / = − = − +Q -Q d E Why is there a minus sign????
Definition of capacitanceCapacitanceCmeasures:Q- howmuch chargeQwe mustCput on the platesAV- to achieve a certain potentialdifference △.Forparallel-plate capacitor:+++(Q / A)+AV+60++
Definition of capacitance V Q C = Capacitance C measures: - how much charge Q we must put on the plates - to achieve a certain potential difference ΔV. + + + + + + + - - - - - - - For parallel-plate capacitor: ( ) d Q A V 0 / =
Definition of capacitanceCapacitanceCmeasures:Q- how much charge Qwe mustCput on the platesAV- to achieve a certain potentialdifference △V.Forparallel-plate capacitor:++A= area of plates++AUnits: the Farad (F)+d++d = separation of plates
Definition of capacitance V Q C = Capacitance C measures: - how much charge Q we must put on the plates - to achieve a certain potential difference ΔV. + + + + + + + - - - - - - - For parallel-plate capacitor: d A C 0 = A = area of plates d = separation of plates Units: the Farad (F)
Try to pull the plates apart..+F+otherplate+++byplateOL++
- - - - - - - + + + + + + + Try to pull the plates apart. Eother plate Fby plate Fby you