# The capacitance of capacitor and energy.

Discussion in 'General Electronics Chat' started by TAKYMOUNIR, May 27, 2015.

1. ### TAKYMOUNIR Thread Starter Active Member

Jun 23, 2008
351
1
If the capacitor has 100 v limit and its capacitance is 1uF ,this mean that the max. energy is 1/2CV*2=5 m J
or I can put more energy on the cap.

Last edited: May 28, 2015
2. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,071
milli G ????

0.5mJ is all you can put in it...

3. ### ian field AAC Fanatic!

Oct 27, 2012
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You can't even cheat with electrolytics - if you supply a current limited higher voltage just under the critical leakage point, the oxide dielectric will form thicker to withstand a higher voltage - but the effectively greater spacing between the plates results in proportionately lower capacitance.

4. ### ErnieM AAC Fanatic!

Apr 24, 2011
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If this is a real world capacitor don't put 100V across it, not if you want the cap to survive for the long term.

75V is better. I would limit it to 50V.

5. ### ian field AAC Fanatic!

Oct 27, 2012
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If its an electrolytic; the applied voltage is what keeps it formed, at a lower voltage the electrolyte very slowly etches away the oxide dielectric - if you then suddenly apply the full rated voltage without first re-forming the capacitor, it'll probably break down.

As a result of the oxide dielectric getting thinner, the capacitance increases.

If the TS is going to the trouble of calculating the energy for a given voltage/capacitance, the exact value of capacitance may be important.

6. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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Without parentheses, it is easy to misinterpret your equation. I am assuming that you mean $\frac{1}{2}CV^{2}$

I get $5 mJ$

My work is shown below...

$10^{-6}*10^{4}*\ .5=.005J\ or\ 5mJ$

Oct 2, 2009
5,451
1,071
Yep...