How and why does voltage lag current in a purely capacitive AC circuit?

[PLW]

Hi guys, I have no idea if this makes any sense, but I’ll give it ago with the hope of getting a better understanding.

I know that a capacitor is a device used to store electric charge and that it charges and discharges at a rate determined by the frequency (50hz in the UK). As the supply voltage (230 volts) increases and decreases the capacitor charges and discharges. I understand that the current is at its minimum when the applied voltage is at its maximum, and that when the voltage is at is minimum the current is at its maximum.

However what I am struggling to understand is how voltage can lag current. My understanding is that voltage is the driving force of the circuit, which causes current to flow against a circuits resistance. I have read that, current must first flow to the 2 plates of the capacitor, where charge is then stored. Only after charge accumulates at the plates of the capacitor is a voltage difference established. The behavior of the voltage is dependent upon the behavior of the current. Or in simple terms current must flow to build up voltage. I can’t see how this happens, when voltage is required to drive current.

I can’t get my head around the fact the voltage is dependent upon current or that voltage lags current, what is it about the capacitor that causes this to happen. how does the current flow if the voltage is lagging behind?

I'd appreciate it, a lot of someone could give explain this without confusing me. Thanks guys.

 

[The Ghost]

current lag and lead - http://www.daviddarling.info/encyclopedia/C/current_lag_and_lead.html I find this hard to explain without diagrams so the link may help. Or

there are a lot of resources which explain this very graphically. What is really being looked at though is Power Factor i.e. at unity (1) there is no waste of supply as in resistance loads like heaters. You might benefit from joining the trainee forum.

 

[Wilko]

I'll try a DC example - attach a 1000uF capacitor to a 6V battery (say), there may be a spark seen from the inrush of electrons to charge the capacitor (as you mention). At the same time this current was maxing, the battery voltage has dipped due to this load (and circuit/battery impedance). After a second or two the voltage on the capacitor and battery will return to 6V and the current will have dropped to zero. So current peaks at the start and the voltage peaks later (at least in my simple mind). For AC the voltage is continually changing and so this cycle of current leading the voltage repeats as per Vs post. I'll need another drink now