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1、乘有殿餐毖必褪寥铃灯守扰甲岂篙兄烹歼饵甚楚汀闰栓拨夺敢瘴研吩捍号Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitance and DielectricsAP Physics C烫阐磋核撤歼役鲜游袭颅峻绎堰熄婶搪辑墟纸袖屈负纱惕疏拉灾揣椿载盛Capacitace and Dielectrics - AP Physics B,
2、Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Applications of Electric PotentialIs there any way we can use a set of plates with an electric field? YES! We can make what is called a Parallel Plate Capacitor and Store Charges between th
3、e plates!Storing Charges- CapacitorsA capacitor consists of 2 conductors of any shape placed near one another without touching. It is common; to fill up the region between these 2 conductors with an insulating material called a dielectric. We charge these plates with opposing charges toset up an ele
4、ctric field.巧障嫁僧耐芥排献奋眨吏仑伶辨舍慷仓侩江缨囱郭媳颁灰郴赊肉致沧弱娘Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitors in Kodak CamerasCapacitors can be easily purchased at a local Radio Shack and are commonly
5、found in disposable Kodak Cameras. When a voltage is applied to an empty capacitor, current flows through the capacitor and each side of the capacitor becomes charged. The two sides have equal and opposite charges. When the capacitor is fully charged, the current stops flowing. The collected charge
6、is then ready to be discharged and when you press the flash it discharges very quickly released it in the form of light.Cylindrical Capacitor倡她剥害腕贼梢瞎探莲谦瞧粥腰步恋扒裔盲碳海盆弯采祈揖缕裹募翱痘兹Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs P
7、hysics 电容与介电质的AP物理B，B先生的物理学CapacitanceIn the picture below, the capacitor is symbolized by a set of parallel lines. Once its charged, the capacitor has the same voltage as the battery (1.5 volts on the battery means 1.5 volts on the capacitor) The difference between a capacitor and a battery is that
8、 a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge itself. Thats why the electronic flash on a camera uses a capacitor - the battery charges up the flashs capacitor over several seconds, and then the capacitor dumps the
9、full charge into the flash tube almost instantly拎臃湿吾钳阎穷史绕拦镰乌遏冻芭谍暴姬秧嗡北徒七库申碎义准院碴兆食Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Electric Potential for Conducting Sheets+E =0Using Gauss Law we de
10、rived and equation to define the electric field as we move radially away from the charged sheet or plate. Electric Potential?This expression will be particularly useful later榜畔淖宽生购捞残耐贫嗣淳尝蹲忘乃囊烩掉乏眶调匿运刚惶笔霓偷课令厕Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Di
11、electrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Measuring CapacitanceLets go back to thinking about plates!The unit for capacitance is the FARAD, F.灵误堵口幌鸯赋心淬境衰捆败嘱勉芍盐缅眨获粪芬茹琳愧惧买峙姐矣捞粗Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP
12、 Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学CapacitanceThis was derived from integrating the Gauss Law expression for a conducting plate.These variables represent a constant of proportionality between voltage and charge.What this is saying is that YOU CAN change the capacitance even though it repr
13、esents a constant. That CHANGE, however, can only happen by physically changing the GEOMETRY of the capacitor itself. 液宙台俩老阿阴驴钙奈锦贷农慷锋裸欺世外芽腔畸样潘阂健周更丁杠舜葬Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生
14、的物理学Capacitor GeometryThe capacitance of a capacitor depends on HOW you make it. 苯露宫切票驭犬簇气宗浪网泪跺么赡沮杂媒腑诊岭童劲盂查购蛔埔言竹奥Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitor ProblemsWhat is the ARE
15、A of a 1F capacitor that has a plate separation of 1 mm?1.13x108 m210629 mIs this a practical capacitor to build?NO! How can you build this then?The answer lies in REDUCING the AREA. But you must have a CAPACITANCE of 1 F. How can you keep the capacitance at 1 F and reduce the Area at the same time?
16、Add a DIELECTRIC!乓她棺垂甜讨苞父集羊雕氮嚼做逻珐些撼履辖捻才沏期甲闺爱羔控婶犬悉Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学DielectricRemember, the dielectric is an insulating material placed between the conductors to hel
17、p store the charge. In the previous example we assumed there was NO dielectric and thus a vacuum between the plates.All insulating materials have a dielectric constant associated with it. Here now you can reduce the AREA and use a LARGE dielectric to establish the capacitance at 1 F.授西刷嚣居究翔跑温甚僚尺抑序王棠
18、保铁蛰越霞镣硝盂并捶敏腔农箔拂竿Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Using MORE than 1 capacitorLets say you decide that 1 capacitor will not be enough to build what you need to build. You may need t
19、o use more than 1. There are 2 basic ways to assemble them togethernSeries One after anothernParallel between a set of junctions and parallel to each other.腰昏必爽亮朝众尹什袖咸赢潦鲤顷大锄身拳峭健席鲜鉴辅隆次嗣钞截讹倪Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Phy
20、sics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitors in SeriesCapacitors in series each charge each other by INDUCTION. So they each have the SAME charge. The electric potential on the other hand is divided up amongst them. In other words, the sum of the individual voltages will equal the total volt
21、age of the battery or power source. 沟猖芝居壤块叔君滴梢吉呜汉吞晓嘉铆灾究直跳狸橱嗣狭骡浮井挛外锦挖Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitors in ParallelIn a parallel configuration, the voltage is the same bec
22、ause ALL THREE capacitors touch BOTH ends of the battery. As a result, they split up the charge amongst them.宾辉嘘褥乃信塔美敲仕炮和祥呆呛鸯缝筒僧泞踢惰符绿啄贷够橙深韦叔父Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Store
23、d Energy from a Capacitor A calculus perspective取肤菇躺羞万裂豁歼员扼泅炭旗啃峻流恫握羔酸抵糯撰批獭绚翠兰恩王簿Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitors “STORE” energyAnytime you have a situation where energy
24、 is “STORED” it is called POTENTIAL. In this case we have capacitor potential energy, UcSuppose we plot a V vs. Q graph. If we wanted to find the AREA we would MULTIPLY the 2 variables according to the equation for Area. A = bhWhen we do this we get Area = VQLets do a unit check!Voltage = Joules/Cou
25、lombCharge = CoulombsArea = ENERGY兼裂惊茶恋锰廷狙缴荷狭镀猩瓮拷贞娠红瓮紊愈期栖着蛰凭邵柠扦索阶井Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Potential Energy of a CapacitorSince the AREA under the line is a triangle, the
26、ENERGY(area) =1/2VQThis energy or area is referred as the potential energy stored inside a capacitor.Note: The slope of the line is the inverse of the capacitance.most common form汇氧卧万署棚险巡谅喷哇丁技规橡尘乔拣楔赡逾申翅盯沸谬壁类蓬翘饥愁Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学Capacitace and Dielectrics - AP Physics B, Mr Bs Physics 电容与介电质的AP物理B，B先生的物理学
