Capacitance inversely proportional to voltage?

Question

I just cant fathom why capacitance is inversely proportional to voltage. Maybe its my understanding of voltage or lack thereof. Voltage is the difference of potential energy between two points. 1 volt is equal to the force required to move 1 coulomb of charge past an arbitrary point in 1 second. So voltage measures how much energy is imparted to each coulomb of charge. Capacitance is when a dielectric keeps oppositely charged plates from equalizing there EMF. The formula for capacitance is C=Q/V. The Q I get because the more charge you have on either plate the more capacitance you will have. Voltage is the force that drives the charges apart. Some help in clarifying this would be great.

V/R

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dougw · Accepted Answer

An analogy is water in a bucket - the bucket being the capacitor and the water is the charge.

The voltage is the water depth.

If you make the diameter of the bucket bigger (bigger capacitor) the same amount of water (charge) will have a lower depth (voltage).

NigelB · Answer

You seem to have forgotten that it is 1/Ct on the left hand side.

So for example if you had two huge capacitances of 0.5 and put them in series, the equation would go:

1/Ct = 1/0.5 +1/0.5 = 2 + 2 = 4

which gives Ct = 1/4 = 0.25

So Ct is lower even though you are adding two large numbers, as the large numbers are adding up to 1/Ct not to Ct, and the reciprocal of a large number is a small one (and vice versa, as you correctly observed)

I hope that helps

Capacitance inversely proportional to voltage?

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