# Physics Capacitance Question help!

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#1
I read somewhere that "Capacitance is constant when voltage is changed, whereas charge is not". Could someone please explain to me in simple terms why this is the case?
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7 years ago
#2
(Original post by jtbteddy)
I read somewhere that "Capacitance is constant when voltage is changed, whereas charge is not". Could someone please explain to me in simple terms why this is the case?
capacitance is a property of the material. Charge is not, so charge can change, for example as voltage increases.
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#3
(Original post by pepeeglesfield)
capacitance is a property of the material. Charge is not, so charge can change, for example as voltage increases.
But isn't "charge" the charge an electron carries? In that case, it remains unchanged regardless of the capacitance of a material?
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7 years ago
#4
(Original post by jtbteddy)
But isn't "charge" the charge an electron carries? In that case, it remains unchanged regardless of the capacitance of a material?
But there is more than one electron flowing at any one time. The amount varies with voltage.
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7 years ago
#5
I suppose the charge in question isn't just the charge of a single electron; it is the total charge flowing. As above.
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7 years ago
#6
(Original post by jtbteddy)
I read somewhere that "Capacitance is constant when voltage is changed, whereas charge is not". Could someone please explain to me in simple terms why this is the case?
The capacitance of something depends on its shape and size and what it's made of. Once you've constructed it the capacitance is fixed and constant.
Then as you add charge to it, the pd increases.
The formula is V= Q/C

As you increase Q, V increases. C is constant.

If you want it in simple terms, think of the capacitance as the capacity (volume) of a container. Once you have your container its volume is fixed.
As you fill it with water (charge) the depth of the liquid (pd) inside increases.
Adding water (charge) doesn't change the actual capacity (capacitance) of the container.
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#7
Thank you for your help, everyone! I understand it now.
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