# simple question

Discussion in 'General Electronics Discussion' started by shadowflare99, Aug 8, 2012.

29
0
Aug 7, 2012
did a condensator

4 uF at 220 Volt = 1.00 Coloumb
have semilar job to a 3 uF at 400 V = 1.20 Coloumb...

did the 20 % can make a really change in a system ?

It's for a Fan...

thank you

Last edited: Aug 13, 2012
2. ### john monks

693
3
Mar 9, 2012
No.
A Farad is a unity of capacity of a capacitor.
The relationships are as follows:
One coulomb is 6.24 X 10^18 electrons.
One coulomb is equal to one ampere passing through a point for one second.
One farad charged to one volt is one coulomb.
the voltage on a capacitor is proportional to the charge on a capacitor or the coulombs of charge.
The charge piles up on one plate of the capacitor and an equal deficit of electrons occurs on the other plate.

Now you should be able to figure out how many coulombs of charge is on a one Farad capacitor at 220 Volts.

Last edited: Aug 8, 2012
3. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,500
2,840
Jan 21, 2010
I'm pretty sure there aren't any commercially available 3F 400V capacitors.

Could it be 3uF?

4. ### CDRIVEHauling 10' pipe on a Trek Shift3

4,960
652
May 8, 2012
How big might that be? Perhaps the size of a 50gal drum? Baybe bigger?..1960's vintage Buick?

29
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Aug 7, 2012
Oopps it's my error it's was 3UF 400

but i understand, because i didn't found a 4 uF at 220 V ..

can i replace it by another thing ?

6. ### CDRIVEHauling 10' pipe on a Trek Shift3

4,960
652
May 8, 2012
Hard to tell. We don't know what circuit this is in.

29
0
Aug 7, 2012
Ok.... I will try to find the same capacitor ... Thank you..

8. ### gorgon

603
24
Jun 6, 2011
4.7uF is a standard value, and you don't want to use a capacitor up to its max voltage. I would never go further than 80% of the voltage on a regular basis.

You should also know that most elecrolytic capacitors has low accuracy, and may have 10-20% more 'uF' than the marked value. So if you need an exact value you need to measure it yourself and make your calculations from that.

TOK