Capacitor and Dielectric -1000773510
Capacitor and Dielectric
Agenda today l.Capacitance(电容) 2.Combination of capacitor 2.Gauss's law in dielectrics(电介质） 3.Energy of electric field
Agenda today 1. Capacitance（电容） 2. Combination of capacitor 2. Gauss’s law in dielectrics （电介质） 3. Energy of electric field
Capacitor: A pair of conductors,whether separated by empty space or nonconducting material,forms a capacitor Capacitor is a useful device to store energy and charge Capacitance:(电容) The constant that is the charge on either plate of the capacitor divided by potential difference of two plates 1F=1C/V AU
Capacitor: A pair of conductors, whether separated by empty space or nonconducting material , forms a capacitor Capacitance:（电容） The constant that is the charge on either plate of the capacitor divided by potential difference of two plates Capacitor is a useful device to store energy and charge 1F=1C/V
The parallel plate Capacitor(平行板电容器 E= E 0 U,-Un=[E.di-Ed-9d S A Capacitance: U
The parallel plate Capacitor(平行板电容器) -Q d + + + + + - - - - - A B +Q E S d S U U q C o A B Capacitance:
The cylindrical Capacitor(柱形电容器) By Gauss's law: E 2m8,rl s-E-2 qdr △U= R 2πE R capacitance C=. 2π61 △U In Rg/Ra
The cylindrical Capacitor（柱形电容器） l RA By Gauss’s law： RB A B o R R l q U ln 2 h r B A o R R l U q C ln 2 capacitance
The spherical capacitor(球电容器 E= 4π6。r1 △U= gdr ,4rr 4π6。 R Ra C=9 RARB △U =4rR。-R4 when Rg-→oo C=4π6R
The spherical capacitor（球电容器） RA RB B A A B o R R R R U q C 4
Energy in capacitor dq a If we want move dq from the plate with negative charge to the positive one,the work needed is: duuldid
Energy in capacitor dq -q +q If we want move dq from the plate with negative charge to the positive one, the work needed is:
5小12g呈 Because Q=CU,the result can also be written as: 号r 2
Because Q=CU, the result can also be written as:
Capacitors in parallel g=CV,4=C,U,…UC宁c宁c= 9=q+9+…+qn=(C+C2+…Cn)U The equivalent capacitance =号=G+C++C
Capacitors in parallel , , U C1 C2 C3 q1 C1 U q2 C2 U q q1 q2 qn C1 C2 Cn U The equivalent capacitance
Capacitor in series 号培共 U-+,…U,-G++ The equivalent 1J11.1 一十 capacitance
Capacitor in series C1 C2 Cn U The equivalent capacitance