Notices
Results 1 to 2 of 2

Thread: capacitor

  1. #1 capacitor 
    Forum Freshman
    Join Date
    Nov 2006
    Posts
    5
    assume an 80 mF capacitor is initially connected to a 9V battery. The battery is then removed and a wire is connected between the two terminals of the capacitor. What is the charge on the capacitor after the wire is connected?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Masters Degree bit4bit's Avatar
    Join Date
    Jul 2007
    Posts
    621
    Assuming the capacitor was fully charged before the battery was disconnected, then the voltage across it would be equal to that of the battery, 9V.

    Q = CV

    ..so the charge across the capacitor would be,

    Q_initial = (80*10^-3)*9
    = 0.72 C

    The charge on the capacitor after the wire is connected is given by the expression:

    Q = Q_initial *e^(-t/CR)

    where:

    t = time
    C = capacitance = 0.08F
    R = resistance of wire

    You can see, the charge is a function of the load resistance, and the time as well as the initial charge.


    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •