do I need a current source to load an electrolytic capacitor? [closed]

I am working with an electrolytic capacitor of 10 000 uF. To load it, do I need a voltage or a current too ? are there charges from my voltage source ? Or is it only in the ceramic capacitor case that you need a charges source ?

Thanks

closed as unclear what you're asking by Rev1.0, PlasmaHH, Bimpelrekkie, Daniel Grillo, Brian CarltonOct 11 '16 at 19:48

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• What are you trying to achieve with a 10 mF cap if you have no clue how to use it ? are there charges from my voltage source That sentence makes no sense. – Bimpelrekkie Oct 11 '16 at 8:02
• I just want to load this 10 mF cap. My question is : do electrons really flow from my voltage source to my cap to load it ? Or a voltage difference is enough to load an electrolytic capacitor ? – velleda Oct 11 '16 at 8:07
• If you want to understand this thing about electrons, currents and capacitors, why not get a book about that from your local library and start reading. Many of us started out like that. Those books are there for everyone to read. – Bimpelrekkie Oct 11 '16 at 8:22

1) capacitors are charged not loaded

2) in general you charge a capacitor by applying a DC voltage to it. Charging stops when the voltage has been reached

3) You can also use a current source to charge a capacitor but you have to observe the voltage as that will keep rising until you stop charging. Capacitors have a rated voltage, never exceed that voltage or it might explode. When charging with a current this needs special attention.

4) a 10 000 uF cap can store a lot of energy and this is proportional to the voltage it is charged to / you want to charge it to.

5) when trying to charge an empty (uncharged) capacitor, a lot of current can flow. Use a supply with current limiting (a lab supply is ideal) or use a series resistor.

6) when discharging such a capacitor it is also advised to have at least some series resistance.

7) if the above makes no sense to you perhaps you should try to understand electronics a bit more before messing around with large capacitors.

• To be exact, the stored energy is proportional to the square voltage :) Nice and thorough explanation! – Marko Gulin Oct 11 '16 at 9:36
• Correct, I knew it wasn't linear so I kept it vague and wrote "proportional" ;-) I was too lazy to think about the real relation ;-) – Bimpelrekkie Oct 11 '16 at 10:10

Honestly, I don't understand what do you mean. Capacitors are charged with charge carriers (electrons), and a source of these electrons can be either a voltage or a current source.

Please be careful - if you place a capacitor in parallel to a voltage source, a very high current might flow into capacitor, since for stepwise voltage change, the capacitor current is determined by:

$$I_C = \frac{\Delta V}{R} \exp\left(-\frac{t}{T}\right), \quad T=R\cdot C ,$$

where $C$ is the capacitance of the capacitor, and $R$ is its ESR (usually around $20-50~\text{m}\Omega$). E.g., for a voltage change of $\Delta V = 10~\text{V}$, capacitance of $C = 0.01~\text{F}$, and resistance of $R=0.01~\Omega$, the current peak is $I_{peak} = 1000~\text{A}$, wheras current drops to $0~\text{A}$ in $5T= 0.5~\text{ms}$.

Voltage is the potential difference between two points. It is N×m/Coulomb. The difference of the charge of two points/objects. Current is measures in coloumbs/second, where Coloumbs are a quantity of charge. Capacitors store farads, which are columbs/volt, basically the amount of charge over the potential difference of the charges.

I would sugestion reading physics for scientists and engineers, which is free to get from a variety of collages in a pdf format. to get a better understanding of electromagnetic forces, and how they relate to each other.

For your question, you can choose to control the current you are sending to the capacitor or the voltage, but if you are controlling the current you could accidently create a greater potential difference than the capacitor can stand, which will cause the dielectric material to explode. Which is why most capacitors are charged with a constant voltage, because it is a safer, albeit slower method to charge the capacitor.