What does it mean (Capacitor)

[TotalMadness]

Can anyone tell me what the difference is or how a capacitor will function when one is 40v and 100µF, and the other is 40v and 1000µF?

Thanks

 

[audioguru]

1000uF is 10 times 100uF so it will filter 10 times better.

 

[kpatz]

The µF value is the capacitance. 1000µF can hold 10 times as much charge as a 100µF. The 40V is the maximum voltage rating of the capacitor, and should always be higher than the highest voltage it will see in your circuit.

 

[Ratchit]

kpatz,

The µF value is the capacitance. 1000µF can hold 10 times as much charge as a 100µF. The 40V is the maximum voltage rating of the capacitor, and should always be higher than the highest voltage it will see in your circuit.

What you really mean to say is that the 1000µf cap will store 10 times the electrical energy of a 100µf cap, when both are at the same voltage. The net stored charge of any capacitor at any voltage is zero. That is because any charge that is accumulated on one plate is depleted by an equal amount on the opposite plate.

Ratch

 

[birdman0_o]

Ratchit, do not drag your other thread onto this simple question. Also note the difference between net charge and total charge. 1 electron and 1 proton is a net charge of 0. 20 electrons and 20 protons is a net charge of 0. The 2nd option has 20 times more charge than the first. Energy is related to charge. Let go of this point that you seem to enjoy arguing way too much.

To the original poster, how it will behave depends completely on the circuit it is in!

 

[crutschow]

kpatz,

What you really mean to say is that the 1000µf cap will store 10 times the electrical energy of a 100µf cap, when both are at the same voltage. The net stored charge of any capacitor at any voltage is zero. That is because any charge that is accumulated on one plate is depleted by an equal amount on the opposite plate.

I find it curious the way you like to generate or expand definitions of common electrical terms in a way that nobody else uses and is contrary to common usage. Obviously you delight in trying to confuse the neophytes out there.

Certainly the net charge on a capacitor is always zero. But when engineers (not lawyers) refer to charge on a capacitor they are not referring to net charge, they are referring to accumulated charge on one of the plates. (kpatz did not say net charge). That is the charge that the equation Q=V*C references, as I assume you know.

You can, of course, continue to keep referring to the net charge on a capacitor when someone mentions capacitor charge, but you are a minority of one in that interpretation.

 

[BrownOut]

but you are a minority of one

Or as someone more aptly put it; both a leader and follower of a cult of one.

 

[tvtech]

Keep it simple Ratch. Otherwise you scare the OP away. Lost to ETO forever.

Visitors want simple answers to basic questions. Not lot's of complicated stuff.

I could turn an ordinary piece of Copper Wire into a complicated discussion if I wanted to: Production processes and all. Temperatures. Draw length. Copper strength. Copper cooling ability VS Aluminum. And so on.

Cheers

 

[TotalMadness]

Thanks all for your replies.

1000uF is 10 times 100uF so it will filter 10 times better.

Could you explain what you mean by filter?

To the original poster, how it will behave depends completely on the circuit it is in!

Ok, nothing is easy to start with. I'm really asking because obviously I need to know whether I would even need one in a circuit. What I think I now know is that it is the maxium charge the capacitor will carry; or, how big the spark will be when you short it out.

Visitors want simple answers to basic questions. Not lot's of complicated stuff.Cheers

Yes, simple is good. Maybe I should ask: why would I choose a 100uF instead of 1000uF? Maybe if someone could point to a test I could do to see what happens when different values are used. I understand for example that a capacitor can be used to smooth out a wave, but do not see why the farad used would make a difference. Just guessing: maybe it has something to do with the speed that a capacitor will charge?

 

[BrownOut]

The farads is a meausre of the capacity. In a smoothing operation, more farads means more smoothing. That's what was meant by "10 times better filter", because a filter is just a smoother.

As a simple example, consider a capacitor with "F" farads connected to a current source of 1mA. Then:

V(capacitor) = 1/F*1mA*T, where T is the time elapsed starting from when the current was applied. Now, you see if the farad ("F" in this example) is bigger, then the voltage is lower for the same current and time. And thus, the ability of the capacitor to store the charge (the "capacity") is increased for more farads.

 

[KeepItSimpleStupid]

If you want a rule for line frequency filtering: Greater than or equal to 1000 uf per amp of designed current.

I need to be able to draw pretty pictures. Picture a full wave rectifier on an AC of say 60 Hz. The bottoms of the sine wave are inverted and you get a ripple frequency of 120 Hz. Assume that you draw no current from it. Now put a capacitor, really doesn't matter the size, it will basically charge to the peak voltage.

Now, when you start to draw current from this, the voltage tends to look like a repeating downward ramp. The bigger the cap, the smaller the ramp height.

As you increase the frequency, the components tend to shrink and so does the capacitance required for the same amount of design current.

Why do audio freaks put greater than 1 Farad caps in their car for their audio system? See: 3 - 4.9 Farad | Capacitors | Car Amplifier Installation & Accessories | Car Audio/Video Installation & Accessories | Car Audio, Video & GPS at Sonic Electronix

 

[Ratchit]

birdman0_o,

Ratchit, do not drag your other thread onto this simple question.

Did I reference any other thread? If not, then I am not dragging in anything.

Also note the difference between net charge and total charge.

They are both zero for a difference of zero.

1 electron and 1 proton is a net charge of 0. 20 electrons and 20 protons is a net charge of 0.

We are talking about the accumulation and depletion of free electrons on the plates. What does the atomic structure of the atom, specifically the protons have to do with anything?

The 2nd option has 20 times more charge than the first.

How do you figure that?

Energy is related to charge.

It is also related to voltage and capacitance.

Let go of this point that you seem to enjoy arguing way too much.

What point is that?

Ratch

 

[Ratchit]

crutschow,

I find it curious the way you like to generate or expand definitions of common electrical terms in a way that nobody else uses and is contrary to common usage. Obviously you delight in trying to confuse the neophytes out there.

Not true. There are a lot of folks who think that a capacitor has more coulombs in it when it is "charged up". If they believe that, then they are confused on their own.

But when engineers (not lawyers) refer to charge on a capacitor they are not referring to net charge, they are referring to accumulated charge on one of the plates.

I don't think lawyers get involved with capacitors very much. Can you find any documentation that says a charge on a capacitor refers to the imbalance of coulombs between the two plates? That is, the accumulation of charge on one plate, AND the depletion of charge on the opposite place. It is true, but can you find documentation?

You can, of course, continue to keep referring to the net charge on a capacitor when someone mentions capacitor charge, but you are a minority of one in that interpretation.

Capacitors get charged with energy, not coulombs. That is a physical fact. Charging with energy means a charge imbalance of coulombs between the plates. If that is what is meant by "charging" a capacitor, I have no problem with that. But I bet a lot of folks don't know that.

Ratch

 

[Ratchit]

tvtech,

Keep it simple Ratch. Otherwise you scare the OP away. Lost to ETO forever.

You are making a lot of assumptions. Specifically that the OP will not be able to think for him/herself, will not understand my response as well as other's, will have such a fragile id that s/he will be afraid to read or ask any questions. Where do you get such notions? By the way, I did not repond to the OP. Notice that?

Visitors want simple answers to basic questions. Not lot's of complicated stuff.

I agree, but correctness counts too, doesn't it? But since when is a basic definition of a word complicated. If you don't agree with my definition, call it a disagreement, not complicated, and say why you don't agree with it.

I could turn an ordinary piece of Copper Wire into a complicated discussion if I wanted to: Production processes and all. Temperatures. Draw length. Copper strength. Copper cooling ability VS Aluminum. And so on.

So could anyone, but would it be relevant to the question?

Ratch

 

[crutschow]

I don't think lawyers get involved with capacitors very much. Can you find any documentation that says a charge on a capacitor refers to the imbalance of coulombs between the two plates? That is, the accumulation of charge on one plate, AND the depletion of charge on the opposite place. It is true, but can you find documentation?

Of course lawyers don't get involved with capacitors much. I was being facetious, since all your posts have a legalistic tenor to the prose, but I guess you didn't pick up on that, or chose not to.

If you agree that the charge on a capacitor is the accumulation of charge on one plate and the depletion on the other, then why do you want me to search for documentation for that? Are you implying that you know of no documentation to that effect?

 

[Ratchit]

crutschow,

If you agree that the charge on a capacitor is the accumulation of charge on one plate and the depletion on the other, then why do you want me to search for documentation for that? Are you implying that you know of no documentation to that effect?

Correct. I have read descriptions equating capacitors to batteries. Other descriptions say they collect positive charge on one plate and negative charge on the other, implying that positive charges are involved. In reality, positive charges are not involved in capacitors, only the absence of movable negative charges. If you can find a good correct description of how a cap works without spending too much time searching, I would appreciate it.

Ratch

 

[misterT]

If you can find a good correct description of how a cap works without spending too much time searching, I would appreciate it.

Here is one: https://www.electro-tech-online.com/threads/ac-flowing-through-a-cap-what-actually-happens.116575/

 

[Reloadron]

Here is one: https://www.electro-tech-online.com/threads/ac-flowing-through-a-cap-what-actually-happens.116575/

OMG, the thread from hell..........

Ron

 

[TotalMadness]

V(capacitor) = 1/F*1mA*T, where T is the time elapsed starting from when the current was applied. Now, you see if the farad ("F" in this example) is bigger, then the voltage is lower for the same current and time. And thus, the ability of the capacitor to store the charge (the "capacity") is increased for more farads.

Thanks, I understand now.

 

[Ratchit]

TotalMadness,

Thanks, I understand now.

Do you really?

First of all, the formula you glommed onto is ambiguous. V(capacitor) = 1/F*1mA*T can be interpreted wrongly as V(capacitor) = 1/(F*1mA*T), whereas it should be written as V(capacitor) = (1/F)*1mA*T .

Second, a capacitor loses as much charge as it gains when a voltage is applied across its terminals. This makes its charge change zero for whatever voltage is applied to the capacitor. Whenever you see or hear of someone "charging" a capacitor, they are charging it with energy, not charge carriers (free electrons). In other words, they are "energizing" the capacitor. Do you understand that?

You first asked what the difference between two capacitors with different capacitance. A capacitor is a electrical energy storage element that stores energy in an electric field. A higher value capacitance is able to store more energy at the same voltage. The ability to store and release energy is handy for many electrical functions including filtering.

Ratch