charging capacitors

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mach6rick

Joined Oct 17, 2007
1
In chapter 13 on capacitors, in the diagrams depicting charging and discharging of capacitors, it appears that the arrows indicating current flow are in the opposite direction of what they should be. Current is defined as positive charge flow and while the capaitor is charging positive charge is building up on the positive side of the capacitor. Actually electrons are leaving that side and they flow in the direction of the drawn arrows.
 

Dave

Joined Nov 17, 2003
6,970
In chapter 13 on capacitors, in the diagrams depicting charging and discharging of capacitors, it appears that the arrows indicating current flow are in the opposite direction of what they should be. Current is defined as positive charge flow and while the capaitor is charging positive charge is building up on the positive side of the capacitor. Actually electrons are leaving that side and they flow in the direction of the drawn arrows.
I assume you are referring to the diagrams on the following page: http://www.allaboutcircuits.com/vol_1/chpt_13/1.html

Conventional current flow is defined as positive charge flow, however actual (or real) current flow is defined as negative charge flow, i.e. transfer of electrons. In this e-book the convention used is actual current flow and this is why you see the lines drawn in the way they are.

To conceptually understand it, when the voltage is increasing electrons are stripped from the positive terminal of the capacitor and deposited on the negative terminal - the charge differential is increasing which results in the increasing voltage. Conversely, when the voltage is decreasing electrons are stripped from the negative terminal of the capacitor and deposited on the positive terminal - the charge differential is decreasing which results in the decreasing voltage.

Dave
 
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