In the water analogy of a series circuit, the water leaves the reservoir with a high pressure and then goes through the pipes (wire) until it encounters and lights up a lamp.
What happens to the water now? Does it return to the battery or is it consumed?
I can sense their might not be a quick answer here...any piece of the puzzle would be appreciated.
well, I guess you could picture a turbine there as the equivlent resistance in your series circuit. The force of the water is dissapated, but it flows right back to the source. Kirchoff's current law says the the some total off all the currents flowing into a circuit, but flow out. If there are no leaks in your system, and nothing boils off as steam, all the water dribbles back to your pump. :)
Voltage is lost, power is consumed, but current remains the same. The resistance determines the current. Put another light in the circuit and the total current goes down, in and out. The water can't push in as hard when there is more resistance down the line, but once it comes out the resistance it keeps flowing at the same rate at which it went in. You can think of it as if it were a long string that you are pulling through a tube. Squish the tube and it is harder to pull the string, but all parts of the string move through the tube at the same rate!
Fred - N4IXL
Please remember to remove the <<NOSPAM>> from my email address when replying.
> In the water analogy of a series circuit, the water leaves the reservoir with > a high pressure and then goes through the pipes (wire) until it encounters and > lights up a lamp.
> What happens to the water now? Does it return to the battery or is it > consumed?
> I can sense their might not be a quick answer here...any piece of the puzzle > would be appreciated.
pch...@canada.com (pete) wrote: > In the water analogy of a series circuit, the water leaves the > reservoir with a high pressure and then goes through the pipes > (wire) until it encounters and lights up a lamp.
> What happens to the water now? Does it return to the battery > or is it consumed?
Think of it this way. You have a system which is filled with water. You have a pump that moves (circulates) the water through the system and then you have a "load" which the current of water makes do something. You used a light, so we'll stick with that. So with your system, you turn on the pump and the water is circulated through the pipes, through the light which causes it to turn on and then back to the pump again to continue circulating. You are adding energy to the system through the pump. In this case you use electricity to make the pump circulate the water thus converting the energy into the flow of water. The light uses this energy by taking it back out of the system, converting it to light. So energy into your system via the pump and back out via the light.
Now I think were you might be getting confused when you think of electricity is the common misconception that you have these little electronics flowing out of the postive side of your (for example) battery carrying little packages of energy which are then used in the light, then the little electron travel back to the negative side of the battery empty handed without that energy. This is what often confuses students since this sort of makes sense on one hand, but then again, if it really worked that way, what is different about the electrons before the light and those after? Well nothing! They are electrons after all, a charged particle. They don't lose their charge and they certainly were not carrying little bundles of energy.
Instead, and this is were many books and professors fail to make it clear to students, you have to think of the system as a whole. You add energy to the WHOLE system at the same time with the battery and take it out of the WHOLE system with the light.
One great way I heard it explained once that really made it clear to me is to think of a bicycle wheel. Flip the bike over. Now you grab the peddle with your hand and get the wheel going really fast. You added energy to the system by turning the crank. Now, put your hand on the tire to slow it down. Your hand gets hot and you remove energy from the system through friction with your hand. Now, when you put your hand on the wheel, did the part of the wheel after your hand slow down while the part before your hand was still travelling faster? Of course not! Just like when you spin the pedel, part of the wheel doesn't start moving first while other parts stay still until the whole wheel is turning either. In both cases the WHOLE wheel speeds up or slows down. You are adding and removing energy from the WHOLE wheel, not just the part under your hand.
Yes, the energy removed is concentrated at your hand in the form of friction, or in the case of a circuit, at the light bulb. This is where the energy comes out, but as you hopefully can now see, you removed that energy from THE SYSTEM as a whole, not from just those electronics coming though the lamp at that moment.
On Thu, 20 Jan 2000 18:05:48 GMT, pch...@canada.com (pete) wrote: >In the water analogy of a series circuit, the water leaves the reservoir with >a high pressure and then goes through the pipes (wire) until it encounters and >lights up a lamp.
>What happens to the water now? Does it return to the battery or is it >consumed?
It returns to the reservoir.
Be careful when using this (or any other) analogy. Analogys are often good for explaining a particular concept, but may fail completely with related cncepts.
Electric current always flows in a complete circuit - from one terminal of a voltage source, through the load, and back to the other terminal of the source. The current is the same at all points in a series circuit.
> In the water analogy of a series circuit, the water leaves the reservoir with > a high pressure and then goes through the pipes (wire) until it encounters and > lights up a lamp.
> What happens to the water now?
a pump returns it to the reservoir.
Opinions expressed herein are my own and may not represent those of my employer.
I don't see any fault with the water analogy. The water returns to the resevoir either through the ground, or it evaporates and falls back to the resevoir as rainfall.
pete wrote: > In the water analogy of a series circuit, the water leaves the reservoir with > a high pressure and then goes through the pipes (wire) until it encounters and > lights up a lamp.
> What happens to the water now? Does it return to the battery or is it > consumed?
> I can sense their might not be a quick answer here...any piece of the puzzle > would be appreciated.
In article <g_Hh4.4865$mK.310...@brie.direct.ca>, pch...@canada.com (pete) wrote:
> In the water analogy of a series circuit, the water leaves the reservoir with > a high pressure and then goes through the pipes (wire) until it encounters and > lights up a lamp.
Not exactly. There is no resevoir. The "water" is not provided by the battery, instead it is provided by the wires. Don't forget, in the Water Analogy, we use pre-filled pipes. In real wires, the "stuff that flows" is provided by the atoms of the metal. All metals everywhere contain a sort of "electron fluid."
It's a very common misconception that batteries supply the "water." Instead, batteries act as charge pumps: they take in electrons through one lead, and they spit out the same number of electrons through the other lead. The total number of electrons inside the battery never changes. However, a battery certainly does perform work. It PUSHES charges through itself, and this causes all of the electrons in the external circuit to begin flowing too.
If batteries never lose any electrons, why do they run down? Simple answer: they run out of fuel. A battery is a chemically- powered charge pump. When the "fuel" chemicals have all been converted into waste products, the battery stops working. And, when we "recharge" a battery, we are simply running a chemical reaction backwards. The waste products are turned back into "fuel" chemicals, and it takes energy to do this.
It might help if you mentally get rid of the battery, and replace it with a DC generator. What's inside a DC generator? Wires. There's no place for electrons to build up or be stored. This mental image helps to defeat the incorrect idea that "power supply" means "provider of electrons." In reality, a power supply is an electron pump, not an electron source.
Another water analogy: imagine that a battery is like a pump that's driven by a spring-driven wind-up motor. It can only pump water until its spring unwinds. To wind it back up, force the water to flow backwards through it. Energy is stored in the "spring". The water columns inside the hoses can be used to transmit energy, but the water is obviously not energy, right? This leads to a major insight:
ELECTRICITY IS NOT A FORM OF ENERGY!
Am I totally crazy? No. Think about it. Batteries don't store electrons, and when a battery is "charged",it has just as many electrons as when it is "dead." Also, electrons flow around and around the circuit, and the circuit never loses or gains electrons. Knowing these facts, how could anyone EVER claim that a flow of electricity is a flow of energy? Yet textbook after textbook says that electricity is energy. This is terrible! It prevents everyone from understanding the simple basic facts behind simple circuits.
> What happens to the water now? Does it return to the battery or is it > consumed?
The water is pumped THROUGH the battery and back out through the other terminal. When a real battery operates a real circuit, there is an electric current in the water between the battery plates as well as in the connecting wires. (In other words, "complete circuit" means just what it says, and the path for current also includes the electrolyte of the battery.) Yes, the current in the electron is composed of moving ions and not moving electrons. Nevertheless, it is an electric current (it is a flow of charges.)
> I can sense their might not be a quick answer here...any piece > of the puzzle would be appreciated.
>Am I totally crazy? No. Think about it. Batteries don't >store electrons, and when a battery is "charged",it has just as >many electrons as when it is "dead." Also, electrons flow around >and around the circuit, and the circuit never loses or >gains electrons. Knowing these facts, how could anyone EVER claim >that a flow of electricity is a flow of energy?
Because it's the flow of charge, which can quite reasonably be called "electricity," that transfers the chemical energy of the battery to the heat energy of the lightbulb. The electron stream acts like a drive shaft, and it's not unreasonable to think of energy flowing through a driveshaft. Sort of.
>Yet textbook >after textbook says that electricity is energy. This is terrible!
That's because textbooks have a rather loose definition of "electricity." Alfred North Whitehead addressed the difficulty: "Electricity isn't a _thing_. It's the way things behave."
>It prevents everyone from understanding the simple basic facts >behind simple circuits.
Well, yeah. The problem is that science books are written by people without a lot of love for the physical sciences. Apparently they figure they can sublimate their fear of things like electric power and telecommunications theory by establishing lots of focus groups.
I've had difficulty with the hydraulic analogy because it turns out that people don't know any more about plumbing than they do about electricity.
M Kinsler -- ........................................................................... . 114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059 Home of the "How Things Work" engineering program for adults and kids. See http://www.frognet.net/~kinsler
I too, really like the water analogy. I'm just a hobbiest, and these comments are a big help to me.
Can you give me your thoughts on these analogies: power source = water pump resistor = bottle neck in the pipe line. (voltage decrease?) diode = allows water to pass through in only one direction, the valve will close if water tries to go in the opposite direction. transistor = valve that has two sources of water that can combine to produce a higher volume of water (voltage increase?). If the base has no water, then the collector does not flow. capacitor = Reservoir that will allow a steady supply of water to pass through, but will not allow a fluctuating supply to pass. choke or inductor = freely allows water to pass until too much water comes through, if too much comes through, it will close the gate.
On Fri, 21 Jan 2000 11:24:33 -0700, "Ken" <a...@b.com> wrote: >I too, really like the water analogy. I'm just a hobbiest, and these >comments are a big help to me.
>Can you give me your thoughts on these analogies: >power source = water pump >resistor = bottle neck in the pipe line. (voltage decrease?) >diode = allows water to pass through in only one direction, the valve will >close if water tries to go in the opposite direction. >transistor = valve that has two sources of water that can combine to produce >a higher volume of water (voltage increase?). If the base has no water, >then the collector does not flow.
I'd say the collector-emitter path is a valve that is controlled by the water flow in the base-emitter path - the more flow in the base, the farther open the valve is pushed.
>capacitor = Reservoir that will allow a steady supply of water to pass >through, but will not allow a fluctuating supply to pass.
Someone previously described a cpacitor as a chamber with a rubber diaphram across it - water can flow in from either side, and stretch the diaphram, pushing water out the other side, but can't flow trough it.
>choke or inductor = freely allows water to pass until too much water comes >through, if too much comes through, it will close the gate.
No - it would have to be something that allows a continuous flow (DC), but provides opposition to changing flow. Possibly a paddlewheel in the pipe, with a flywheel on it?
"Ken" <a...@b.com> wrote: > Can you give me your thoughts on these analogies: > resistor = bottle neck in the pipe line. (voltage decrease?)
Or how about a valve?
> transistor = valve that has two sources of water that can combine > to produce a higher volume of water (voltage increase?). If the > base has no water, then the collector does not flow.
One of those water bed filler/drainer devices. <grin>
> capacitor = Reservoir that will allow a steady supply of water to > pass through, but will not allow a fluctuating supply to pass.
No, a capacitor (in a series circuit) tends to block DC (steady current) and pass AC (alternating current). In parallel, maybe you can think of a capacitor like a storage tank or pressure tank on a private well system.
Don't forget the pipes themselves. Pipes = Wires. Like water pipes, the more current flow you are going to need, the larger the wires you need.
I can understand the resistor, diode, and transistor just fine. But I'm having problems with the Capacitor and inductor.
> Someone previously described a cpacitor as a chamber with a rubber > diaphram across it - water can flow in from either side, and stretch > the diaphram, pushing water out the other side, but can't flow trough > it.
Does that mean that water cannot flow through. ie. no current can pass through a capacitor? That doesn't make sense.
And what is the difference between a polarized capacitor (electrolitic) and non-polarized (ceramic).
> >choke or inductor = freely allows water to pass until too much water comes > >through, if too much comes through, it will close the gate.
> No - it would have to be something that allows a continuous flow (DC), > but provides opposition to changing flow. Possibly a paddlewheel in > the pipe, with a flywheel on it?
So it opposes any change in current, but does not oppose a direction (like a diode). ie. It keeps all current at constant levels. I don't know what you mean by paddlewheel and flywheel. (or does it oppose voltage change, not current change??)
On Fri, 21 Jan 2000 14:46:59 -0700, "Ken" <a...@b.com> wrote: > I can understand the resistor, diode, and transistor just fine. But I'm >having problems with the Capacitor and inductor.
>> Someone previously described a cpacitor as a chamber with a rubber >> diaphram across it - water can flow in from either side, and stretch >> the diaphram, pushing water out the other side, but can't flow trough >> it.
>Does that mean that water cannot flow through. ie. no current can pass >through a capacitor? That doesn't make sense.
Yes - direct current cannot flow through a capacitor.
Actually, that water anology is not too bad for describing the action of a bypass capacitor, but doesn't really apply to coupling (DC blocking) capacitors (same part, different use)
>And what is the difference between a polarized capacitor (electrolitic) and >non-polarized (ceramic).
The construction of an electrolytic cap allows a much greater capacity for a given voume than ceramic or other non-polarized construction.
>> No - it would have to be something that allows a continuous flow (DC), >> but provides opposition to changing flow. Possibly a paddlewheel in >> the pipe, with a flywheel on it?
>So it opposes any change in current, but does not oppose a direction (like a >diode). ie. It keeps all current at constant levels. I don't know what >you mean by paddlewheel and flywheel.
An inductor opposes a change of current through it (and a capacitor opposes a change of voltage across it)
I was thinking of a paddlewheel in the pipe that would be turned by the water passing by. A flywheel on the same shaft (outside the pipe) would limit any change in the speed or direction of rotation of the paddlewheel, thereby limiting a change in speed or direction of water flow.
The water analogy may be useful in describing some aspects of electricity, but it breaks down for others.
In article <dqeh8sg8ek75msp370q6anvh5bg255h...@4ax.com> Peter Bennett <pete...@interchange.ubc.ca> writes:
> >choke or inductor = freely allows water to pass until too much water comes > >through, if too much comes through, it will close the gate. > No - it would have to be something that allows a continuous flow (DC), > but provides opposition to changing flow. Possibly a paddlewheel in > the pipe, with a flywheel on it?
Actually, the water itself has 'inductance'. The 'water hammer' effect is the result of a sudden change in flow rate. That air trap is just a snubber. :)
Mark Kinsler wrote: > That's because textbooks have a rather loose definition of "electricity." > Alfred North Whitehead addressed the difficulty: "Electricity isn't a > _thing_. It's the way things behave."
Does the word have any meaning in Science at all? Is it not a word existing only in 'maninthestreetspeak'? The man in the street uses it with his customary lack of precision when he means any of electrical energy, electrical power or electric charge. An interesting point is that he also happily practises Orwellian style 'doublethink' for although only electric charge of these three may be considered a 'thing', people are quite convinced that electricity IS a thing - usually measured in MW, although amps or volts can do just as well. As a secondary school teacher, I know that pupils doggedly hold on to their pr-(mis)conceptions. They won't believe me if I say the word has no precise meaning -the TV announcer uses it and he has far more credibilty than I. Accepting that 'electricity' can not be removed from pupils' vocabularies, I make the best of a bad job and embrace the word for the closest quantity in physics to their already existing concept - that closest quantity I suggest being electric charge. As a rider I freely admit that after two years of my teaching it to them, hardly any pupil has much more idea of it than when they started. But I don't think I am alone in this. After all, everyone (in the UK at least) has studied 'electricity' ('oops - I'm using IT as the name of a subject now) at school. Yet how many have a clue?
> I've had difficulty with the hydraulic analogy because it turns out that > people don't know any more about plumbing than they do about electricity.
> M Kinsler > -- > ........................................................................... . > 114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059 > Home of the "How Things Work" engineering program for adults and kids. > See http://www.frognet.net/~kinsler
>>> Someone previously described a cpacitor as a chamber with a rubber >>> diaphram across it - water can flow in from either side, and stretch >>> the diaphram, pushing water out the other side, but can't flow trough >>> it.
>>Does that mean that water cannot flow through. ie. no current can pass >>through a capacitor? That doesn't make sense.
>Yes - direct current cannot flow through a capacitor.
But alternating current can. It stretches the rubber diaphragm in one direction, pushing water out the other side. When the pressure reverses, the flow reverses. If the diaphragm is stretched such that the pressure against it equals the pressure of the supply, then the water flow will stop.
>Actually, that water anology is not too bad for describing the action >of a bypass capacitor, but doesn't really apply to coupling (DC >blocking) capacitors (same part, different use)
It can certainly apply to a blocking capacitor. The DC component will stretch the diaphragm a considerable amount, and the AC signal component will make the diaphragm deflect a bit in either direction from that stretched position. Remember that there's water on each side of the diaphragm, so the AC variations will be transmitted through the capacitor.
>The water analogy may be useful in describing some aspects of >electricity, but it breaks down for others.
The inductor works pretty well, too. Think of a very long pipe filled with water. Put that in your circuit. You'll find that the inertia of the water therein prevents you from either starting or stopping the flow of water as quickly as you might wish. Thus the current has a tendency to stay constant and free from quick variations.
We can even make hydraulic transformers. These consist of two different-diameter cylinders containing pistons joined by a common connecting rod. A lot of fluid entering the big cylinder at low pressure will eject a small amount of fluid at high pressure from the small cylinder. These are used quite a lot in hydraulic systems and they correspond 1:1 with electric transformers.
M Kinsler
-- ........................................................................... . 114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059 Home of the "How Things Work" engineering program for adults and kids. See http://www.frognet.net/~kinsler
> >>Does that mean that water cannot flow through. ie. no current can pass > >>through a capacitor? That doesn't make sense.
> >Yes - direct current cannot flow through a capacitor.
> But alternating current can. It stretches the rubber diaphragm in one > direction, pushing water out the other side. When the pressure reverses, > the flow reverses. If the diaphragm is stretched such that the pressure > against it equals the pressure of the supply, then the water flow will > stop.
OK. that makes sense. But why would you want AC to flow and not DC? I can understand DC because everything flows in a particular direction. But when you have AC in a circuit, it throws me off.
>> But alternating current can. It stretches the rubber diaphragm in one >> direction, pushing water out the other side. When the pressure reverses, >> the flow reverses. If the diaphragm is stretched such that the pressure >> against it equals the pressure of the supply, then the water flow will >> stop.
>OK. that makes sense. But why would you want AC to flow and not DC? I can >understand DC because everything flows in a particular direction. But when >you have AC in a circuit, it throws me off.
Many devices which handle communications signals convert these into a varying DC voltage. For example, the output of an audio amplifier which uses a 12v power supply might be about 9 volts plus-or-minus 1 volt. That means that the output voltage varies between 8 volts and 10 volts. The variation contains our sound signal, while the 9 volts it varies around is an artifact of the amplifier itself.
We generally analyze such a signal by thinking of it as a DC voltage combined with an AC voltage. In this case, we have a 1v AC voltage (i.e., plus-or-minus one volt) superimposed upon a 9 v DC voltage. We can, and often do, consider the AC and DC components separately.
Now, if we were to apply this signal to a loudspeaker, we would find that the 9v component would cause the speaker's voice coil to conduct a lot of current and overheat. Thus we'll use a "blocking capacitor" in series with the amplifier. This will allow only the _variations_ in the signal to go through the speaker.
M Kinsler
-- ........................................................................... . 114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059 Home of the "How Things Work" engineering program for adults and kids. See http://www.frognet.net/~kinsler
You know, all this analogy stuff is clever, but why not try to understand the actual theory of the operation of the device. I think that is better anyway. Start off with a good understanding of charges. Like charges repel, opposites attract. Now picture little electrons, all with a negative charge moving in one direction, creating a hole or positive charge in it's wake moving in the other direction that another electron can fill.
A capacitor, in it's simples form, is just two conducting plates separated by an insulator. You apply a current and for a time, there is one, as all the little electrons start stacking up on the plate and through their charge creating a positive charge on the other plate. As soon at the capacitor can take no more charge, the current stops and there you are with a big charged capacitor.
If this was an AC current so that you reverse the polarity at your battery and the current would flow right back in the other direction. If the value of the capacitor and frequency of the AC current are correct, they you can flip back and forth all day long charging and unchanging the capacitor and it will act like it isn't even there. But here is the cool part, lower the voltage, and the charge on the capacitor plates leak back into the circuit and it keeps the voltage steady. Small variations in voltage aren't noticed because the capacitor acts like a little backup battery. That is why we say a capacitor resists a change in voltage. Picture the voltage stored as surplus as a charge on those plates, and you will always remember RESISTS A CHANGE IN VOLTAGE.
Now an inductor is a coil of wire, basically an electromagnet. You can think of all those curled up wires as resisting the flow of current in your head without much imagination, but lets see what happens. Current flows in the wire. Each wire sets up a magnetic field created by the electric field flowing through it, these little magnetic fields all interact between each loop of wire. As you flow current into an inductor, it also stores a charge, although unlike the capacitor, it is only for the time current is flowing. This magnetic field impedes the flow of electrons or the current in order to propagate itself. Picture a bunch of turns of wire around a nail and just by connecting them to a battery, you can pick up metal objects. Disconnect the battery and the objects are released. Work is being done somewhere.
Here is the cool part about electrons. The current is impeded as the field builds up on the inductor coil. As soon as you disconnect the power, the field collapses and the moving magnetic lines of force create an electric current in the wire. So you can see here that changes in current are resisted because as the current changes, the magnetic field stored in the inductor can pump some back into the circuit. You can think of the inductor as a generator that can supply current back into the circuit. I think the flywheel analogy is pretty good.
The real advantage to AC is that it can be TRANSFORMED. If you needed 115v of DC at your outlet instead of AC, how would we get it to you? We would either have to send you 115 volts, or send a higher voltage, heating up all the wires, and then waste more energy with resistors to drop the voltage down at your house. Losses in the power lines because of resistance would be so great, we would have to have a power station on every corner. With AC, we can send hundreds of thousands of volts on a line, so that if we lose 10%, who cares? Then we transform it down to tens of thousands of volts, then at the pole going into your house to 240 or 120 or whatever. Then we transform it back to DC to run all the electronics in your house except for heating elements and electric motors.
Your last question about why would we want AC to flow and not DC, is getting into applications. You really will have to get into putting components together and learn progressively to understand that. It is like you are asking about calculus and we are just now learning addition and subtraction. You have to build to that point and be patient.
Capacitors provide several functions, one is to prevent the flow of DC. You might want an audio signal, for example, to be amplified, but want to remove the DC component of that signal. If you couple two stages of a circuit with the right capacitor, an AC (audio, radio, etc.) would pass as if the capacitor wasn't even there, but DC would be blocked. You can also filter things. You wouldn't want to short out your circuit by connecting a positive voltage source directly to ground, but you could do just that with a capacitor. DC would not flow through the capacitor, but certain AC frequencies could. That is how the bass and treble controls in a stereo work. You pass certain frequencies and block others with resistors and capacitors.
Keep plugging. You probably already have head several breakthroughs. Electronics is like that, you hit a plateu and stay frustrated for a while, then when you breakthrough it is a major leap and if seems like dozens of things make sense all of a sudden... until the next wall. :)
>A capacitor, in it's simples form, is just two conducting plates separated >by an insulator. You apply a current and for a time, there is one, as all >the little electrons start stacking up on the plate and through their charge >creating a positive charge on the other plate. As soon at the capacitor can >take no more charge, the current stops and there you are with a big charged >capacitor.
Be careful here. There is, theoretically, no limit to the amount of charge a capacitor can store as long as its dielectric doesn't break down. A capacitor stops charging when the voltage developed across it from the stored charge equals the voltage of the source that's providing that charge.
>If this was an AC current so that you reverse the polarity at your battery >and the current would flow right back in the other direction. If the value >of the capacitor and frequency of the AC current are correct, they you can >flip back and forth all day long charging and unchanging the capacitor and >it will act like it isn't even there.
The frequency is not at all critical. Any capacitor will pass an alternating current at any frequency.
>But here is the cool part, lower the >voltage, and the charge on the capacitor plates leak back into the circuit >and it keeps the voltage steady. Small variations in voltage aren't noticed >because the capacitor acts like a little backup battery. That is why we say >a capacitor resists a change in voltage. Picture the voltage stored as >surplus as a charge on those plates, and you will always remember RESISTS A >CHANGE IN VOLTAGE.
That's a perfectly good model, but it's not always helpful in every case.
>Now an inductor is a coil of wire, basically an electromagnet. You can >think of all those curled up wires as resisting the flow of current in your >head without much imagination, but lets see what happens. Current flows in >the wire. Each wire sets up a magnetic field created by the electric field >flowing through it, these little magnetic fields all interact between each >loop of wire. As you flow current into an inductor, it also stores a >charge, although unlike the capacitor, it is only for the time current is >flowing. This magnetic field impedes the flow of electrons or the current >in order to propagate itself.
It's probably better to think of an inductor as an electric generator that produces a voltage that opposes any change in the current flowing through it. Electrical inertia is a good model for this.
>Picture a bunch of turns of wire around a >nail and just by connecting them to a battery, you can pick up metal >objects. Disconnect the battery and the objects are released. Work is >being done somewhere.
The only work done is when the objects are moved or released, and that has little to do with the self-inductance of the system. An inductor stores and releases energy, ideally in equal measure.
>Here is the cool part about electrons. The current is impeded as the field >builds up on the inductor coil. As soon as you disconnect the power, the >field collapses and the moving magnetic lines of force create an electric >current in the wire. So you can see here that changes in current are >resisted because as the current changes, the magnetic field stored in the >inductor can pump some back into the circuit. You can think of the inductor >as a generator that can supply current back into the circuit. I think the >flywheel analogy is pretty good.
Yup. Inertia.
M Kinsler
-- ........................................................................... . 114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059 Home of the "How Things Work" engineering program for adults and kids. See http://www.frognet.net/~kinsler
Mark Kinsler wrote: > It's probably better to think of an inductor as an electric generator that > produces a voltage that opposes any change in the current flowing through > it. Electrical inertia is a good model for this.
Yes. How about thinking of an inductor as a region where the 'effective mass' of the electron fluid is increased. In regard to this, does a single electron have inductance? It certainly has mass, so accelerates at non infinite rate, stores energy (kinetic) and carries on once the accelerating force is removed. Does the inductance of say a wire consist of two parts - one due to the 'real' mass of the charges and the other due to their magnetic interaction which increases their 'effective' mass? And I think of a capacitor plate as a region where the compressibility of the electron fluid is increased (by the cancellation of the electric fields of each plate by that of the other). So large amounts of this fluid can be added or subtracted with less than the usual pressure increase. The electrons can be packed more densly or more easily removed. One proton and one electron make a capacitor perhaps? Peter Lawton
"Ken" <a...@b.com> wrote: > I can understand the resistor, diode, and transistor just fine. But I'm >having problems with the Capacitor and inductor.
>> Someone previously described a cpacitor as a chamber with a rubber >> diaphram across it - water can flow in from either side, and stretch >> the diaphram, pushing water out the other side, but can't flow trough >> it.
>Does that mean that water cannot flow through. ie. no current can pass >through a capacitor? That doesn't make sense.
You just *might* find the explanation at my web site useful. It's rather basic and uses the dreaded water analogy but I've had good comments from some people who say it helps. It has the advantage of using pretty pictures which are much easier to understand than words :o)
