Lecutre 4 Notes

Properties of the electrons ? Millikan Oil Drop Experiment Apparatus : Chamber Results of the Experiment : oil Air i. ^ i drop 2 Dominant Forces casting on the drops ) : injector mm , + u ; microscope gravity : Taj = Mod g- w/o the Ct > %-) disks = > Mod > measured ✓ É i increase the É disks , = > electric : IE = god É ⊥ some negatively charged droplets slow down and stop , 7=0 Purpose of the electric field ? so when the oil drops fall those that are ⊥ the Id =D ⊥ oil drop injector creates neutral oil negatively charged will feel a repulsion Drops y drops , positively charged oil drops that are positively charged will feel an and negatively charged oil drops attraction towards the negative disk ¥ -0T = F% + F) = 0 = Mod g- ⑦ É= g- measured ⊥ all the oil drops fall due to gravity :q=-M ¥ d# but now they're going to interact with y q the electric field once they get into measured constant the region I Repeated experiments w/ a + V on the bottom and V on the top plate they found the charge on the oil Repeated for ⊥ tv on bottom plate will repulse anything with a positive charge droplets was a constant multiple of many droplets = > ⊥ now they are measuring the properties and charge on charged oil droplet a single value : q=n C- 1.60 ✗ co " C) Y same result ! # charge of q : n ( 1.60 × 10 " c) an e- Fg = Mod g Mod mass of oil drop ( downward ) FE = God É God charge on the oil drop ( upward ) equate the two forces to get charge God always integer multiple of 1.602 × 10 " C tells us oil drops accumulate n charges God = n (-1.602 × 10-19) C for negative drops = n (1.602 × 10-19) ( for positive drops lfelectron = 1.602 × 10 -19C Mod = 9.11 × 10-3 ' kg from Thomson Balance forces gravity will always be the same force due to electric field acts on the charge on the drop flipped so we're interested in the positively charged drops 1. 602 × 10 " C magnitude of the charge on the electron magnitude " elemental charge "