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If I have a 5v capacitor and a 3v power source, and I connect the power source to the capacitor will it charge up to 3v then stop, or will the voltage rise above 3v?

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  • \$\begingroup\$ Why the downvote? \$\endgroup\$ – tpaul Jan 9 '14 at 3:53
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With a static voltage source, a capacitor in series will charge up until its voltage is the same as that of the source.

With a few components you can build a boost converter, which is capable of charging a capacitor beyond the voltage of the supply due to the inductor forcing more charge into the capacitor when the switch is open.

Operating a capacitor near its voltage limit can result in reduced capacitance though, and charging it past its limit may destroy it violently.

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  • \$\begingroup\$ This is almost exactly the information I was looking for right now. If a cap is rated 10v and 100μF, and I apply 5v to it, it will charge up to 5v, as per your answer. But, what about the capacitance? Does it stay to 100μF, or go up to 200μF, or go down to 50μF? \$\endgroup\$ – RichieACC Dec 23 '15 at 8:30
  • \$\begingroup\$ @RichieACC: It would drop very slightly, maybe by about 2% or less. \$\endgroup\$ – Ignacio Vazquez-Abrams Dec 23 '15 at 8:32

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