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Simple Capacitor Question Rate Topic: -----

#1 4 January 2012 - 09:23 AM jerryyu 


Lepton
Does a capacitor only releases energy once it's fully charged up?
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#2 4 January 2012 - 10:37 AM John Cuthber 


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Chemistry Expert
No, or at least not in the normal way of using one.
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#3 27 January 2012 - 07:20 AM user_name 


Lepton
A capacitor will release energy if it has any charge in it (not necessarily full charge). To release energy, a capacitor needs a suitable current.
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#4 27 January 2012 - 03:29 PM Schrödinger's hat 


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Psychic Sexpert

View Postjerryyu, on 4 January 2012 - 09:23 AM, said:

Does a capacitor only releases energy once it's fully charged up?


A capacitor releases energy any time the voltage across whatever it is connected to is less than the voltage across the terminals.
Consider the following:
Charge a capacitor to 1V by attaching it to a power source momentarily.
If you attach it across a piece of wire, or LED, it will release energy into the circuit.
If you attach the positive terminal to the positive terminal, (and - to -) of a 1.4V batter, the capacitor will instead continue charging.

Capacitors that are charged will also leak a small amount of energy because the dielectric is not a perfect insulator. The amount lost depends on how charged the capacitor is. This is (one of the reasons) why we don't use capacitors instead of batteries for long term storage.
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