Saved Bookmarks
| 1. |
A900pFcapacitoris chargedby 100 V sources .Calculatethe electrostaticenergystoredin thecapacitor.Thecapacitoris thendisconnectedfromthe sourceandconnectedto anotheruncharged900pFcapacitor. Findthe commonpotentialof thesystem ? |
|
Answer» Solution :`C_I =900pF =900 XX 10^(-12)F,V_1 =100 V,C_2 =900 V,C_2 =900pF=900 xx 10^(-12) F,V_2=0` `q=CV =900 xx 10^(-12) xx 100= 9 xx 10^(-8)C ` The energystoredin thecapacitoris `U=1/2 CV^2 =1/2qV =1/2 9 xx 10^(-8) xx 100` ` U=4.5 xx 10^(-6) J` whenthe firstcapacitoris disconnectedfromthe SUPPLY andconnectedto antherunchargedcapacitorof capacitance`900^@ pF `potentialdifferenceis `V=(C_1 V_1 +C_2 V_2)/(C_1 +C_2)` `=((900 xx 10^(-12)xx 100)+0)/(900 xx 10^(-12) +900 xx 10^(-12))` `=(9 xx 10^(-8))/(1800 xx 10^(-12))` ` =(9xx 10^(-8))/(18 xx 10^(-10))` `=0.5xx 10^2` `=50 V` 
|
|