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Capacitor question?

  1. Jan 21, 2007 #1
    Why does it take a capacitor longer to charge than to discharge?
     
  2. jcsd
  3. Jan 21, 2007 #2
    In what consist the circuits you use for charging and discharging respectively? The times for charging and discharging depend, besides from the capacitance of the capacitor, on the other components of the circuit.

    For example, in the circuit of a camera flash, you charge the capacitor from a battery which, at the rated voltage, can only debit a limited current. Then you discharge the capacitor on the flash lamp and the discharge current is limited by the flash lamp's resistance, but is far larger than the maximum current of the battery. So in this case the charging time is bigger than the discharging time.

    In the general case, if your charging/discharging circuit is composed of the capacitor and some other (resistive) components which have an overall resistance R (seen at the capacitor's leads), the charging/discharging time will be equal to RC which is called the time constant of the circuit.

    So, if you charge the capacitor through a resistance and then discharge it through a higher resistance the charging time will be lower than the discharging time in this case.
     
    Last edited: Jan 21, 2007
  4. Jan 21, 2007 #3
    Hmm... Usually capacitors are discharged using a resistor. This increases the time taken for it a capacitor to discharge is caused by the increase of resistance.


    In terms of charge:
    http://www.s-cool.co.uk/a-/phy-/ecapac-/a-phy-ecapac-ql3_files/image024.gif
    We can see time (t) is affected by the resistance (R).

    Hope this helps :smile:
     
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