speed of electrons
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bphgravity
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Re: speed of electrons
It is not been determined exactly how fast electrons move trough a conductor. It is only estimated in theory through complicated calculations. The values I have seen is anywhere from between only a few cm in several hours to as fast as several cm in a few minutes. In either case, as voltage is increases the charge impulse is increrased proportionaly to the current flow. This impulse is observed to be near the speed of light. The electrons do not move faster or slower on reference to voltage. It is best to think of electrons as vibrating back and forth very rapidly instead of as forward movement. For you math nuts out there, the calculation is somethingin the order of:
cm/sec = I/QxexR^2xpi=.0023cm/sec=8.4cm/sec
It is not been determined exactly how fast electrons move trough a conductor. It is only estimated in theory through complicated calculations. The values I have seen is anywhere from between only a few cm in several hours to as fast as several cm in a few minutes. In either case, as voltage is increases the charge impulse is increrased proportionaly to the current flow. This impulse is observed to be near the speed of light. The electrons do not move faster or slower on reference to voltage. It is best to think of electrons as vibrating back and forth very rapidly instead of as forward movement. For you math nuts out there, the calculation is somethingin the order of:
cm/sec = I/QxexR^2xpi=.0023cm/sec=8.4cm/sec
charlie
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Re: speed of electrons
Electrons, like anything else with mass, can travel at any speed except the speed of light (sorry Trekers). As an object gains speed, it gains mass (among other things). As an electron or ion approaches the speed of light, much more energy is required to move it just a little faster. This required energy continues to increase until an infinite amount of energy is required to reach the speed of light. At the speed of light, a single electron would have an infinite mass. I think we all know you can't apply an infinite amount of energy and how would you handle an infinite mass? It would be well to read some articles on particle accelerators to get a better handle on this concept.
Electrons, like anything else with mass, can travel at any speed except the speed of light (sorry Trekers). As an object gains speed, it gains mass (among other things). As an electron or ion approaches the speed of light, much more energy is required to move it just a little faster. This required energy continues to increase until an infinite amount of energy is required to reach the speed of light. At the speed of light, a single electron would have an infinite mass. I think we all know you can't apply an infinite amount of energy and how would you handle an infinite mass? It would be well to read some articles on particle accelerators to get a better handle on this concept.
al hildenbrand
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Re: speed of electrons
Frank,
With electrons moving at approx. 1? inches per second and light at 186,000 miles per second, how can current apparently move so fast?
Another Newtonian example occurs to me.
Ever notice the sound of the couplings between cars of a freight train as the train first starts accelerating? The gap in each coupling is moved forward or back (depending on the direction the train moves) one after the next down the length of the train. The cars of the train start inching ahead while the sound, made as the gap in each coupling shifts position, races down the length of the train.
This phenomena is the movement of a single "hole" from one coupling to the next.
[ April 28, 2003, 08:46 AM: Message edited by: al hildenbrand ]
Frank,
With electrons moving at approx. 1? inches per second and light at 186,000 miles per second, how can current apparently move so fast?
Another Newtonian example occurs to me.
Ever notice the sound of the couplings between cars of a freight train as the train first starts accelerating? The gap in each coupling is moved forward or back (depending on the direction the train moves) one after the next down the length of the train. The cars of the train start inching ahead while the sound, made as the gap in each coupling shifts position, races down the length of the train.
This phenomena is the movement of a single "hole" from one coupling to the next.
[ April 28, 2003, 08:46 AM: Message edited by: al hildenbrand ]
jcormack
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Re: speed of electrons
Think of it this way - You have a pipe full of tennis balls (electrons) - You push one in one end and another pops out the other. Voltage represents the amount of force required to push the ball through in a given amount of time. Voltage does not equate to velocity.
Think of it this way - You have a pipe full of tennis balls (electrons) - You push one in one end and another pops out the other. Voltage represents the amount of force required to push the ball through in a given amount of time. Voltage does not equate to velocity.
bphgravity
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Re: speed of electrons
Al, current doesn't move fast at all. You cannot call electrical current and electrical charge the same thing. The current is the movement of the electrons; very slow. The charge moves along with the current and because it has no mass, it will travel at near the speed of light. Does a capacitor store current? How do store movement? Capacitors store charge, which requires minimal current to flow. Simply, the current is the movement and charge is the energy.
Al, current doesn't move fast at all. You cannot call electrical current and electrical charge the same thing. The current is the movement of the electrons; very slow. The charge moves along with the current and because it has no mass, it will travel at near the speed of light. Does a capacitor store current? How do store movement? Capacitors store charge, which requires minimal current to flow. Simply, the current is the movement and charge is the energy.
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Re: speed of electrons
I think I posted this once before, perhaps on the "old forum." But it might help to post it again.
- - - - - - - - - - - - - - - - - - - - -
As current flows through a wire, every electron that moves at all will be moving at (or near) the speed of light. However, any given electron may travel only a very short distance in any given interval of time. Here?s what I mean:
Suppose that one electron (let us call it the ?Red Electron?) is pushed along the wire (the push comes from the battery or the AC generator) from Atom #1 to Atom #2. The jump from one atom to the next happens at the speed of light. Shortly thereafter, an electron will be seen moving from Atom #2 to Atom #3. However, it may or may not be the ?Red Electron.? Perhaps the one that jumps to Atom #3 will be the ?Blue Electron.? You might see the ?Red Electron? circling around Atom #2 for quite some time. It will eventually be pushed along to Atom #3, and may circle around it for a while before moving on to Atom #4. It is in this manner that the ?Red Electron? can be observed to ?drift? along the wire at a human?s walking pace. In reality, a human observer (or an ammeter clamped around the wire) will not be able to distinguish one electron from any other. All that can be observed is that electrons are moving past the observer?s position at the speed of light.
The notion of current (as expressed in amps) comes from counting the number of electrons passing by (each moving at the speed of light) within a period of one second. Perform a unit conversion (like "one foot equals twelve inches") to change "electrons per second" to "coulombs per second," and you will have "amperes."
I think I posted this once before, perhaps on the "old forum." But it might help to post it again.
- - - - - - - - - - - - - - - - - - - - -
As current flows through a wire, every electron that moves at all will be moving at (or near) the speed of light. However, any given electron may travel only a very short distance in any given interval of time. Here?s what I mean:
Suppose that one electron (let us call it the ?Red Electron?) is pushed along the wire (the push comes from the battery or the AC generator) from Atom #1 to Atom #2. The jump from one atom to the next happens at the speed of light. Shortly thereafter, an electron will be seen moving from Atom #2 to Atom #3. However, it may or may not be the ?Red Electron.? Perhaps the one that jumps to Atom #3 will be the ?Blue Electron.? You might see the ?Red Electron? circling around Atom #2 for quite some time. It will eventually be pushed along to Atom #3, and may circle around it for a while before moving on to Atom #4. It is in this manner that the ?Red Electron? can be observed to ?drift? along the wire at a human?s walking pace. In reality, a human observer (or an ammeter clamped around the wire) will not be able to distinguish one electron from any other. All that can be observed is that electrons are moving past the observer?s position at the speed of light.
The notion of current (as expressed in amps) comes from counting the number of electrons passing by (each moving at the speed of light) within a period of one second. Perform a unit conversion (like "one foot equals twelve inches") to change "electrons per second" to "coulombs per second," and you will have "amperes."
Ed MacLaren
Senior Member
Re: speed of electrons
Connect an ammeter in series with a capacitor and have a look. Of course, with DC you will only have a brief surge of current during the charge or discharge period.
Ed
The charge taken by a capacitor is measured in coulombs, and that is a quantity of electrons. Electrons flowing in to, and out of, a capacitor is current.
Connect an ammeter in series with a capacitor and have a look. Of course, with DC you will only have a brief surge of current during the charge or discharge period.
Ed
al hildenbrand
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Re: speed of electrons
Nicely said, Charlie B.
Ed MacLaren's post and diagrams (April 27, 2003 10:26 PM), emphasizes
Modern physics has advanced far enough to show that a given electron barely moves, and that while hopping back and about in its neighborhood, the effect, when observing a point on the conductor, is as if the electrons are traveling the length of the circuit at near light speed.
Bryan,
A capacitor holds charge and current. Voltage and Amperage. Two different properties. Together, they are energy (capable of work). When connected to a complete circuit, the positive ions collected on one plate of the capacitor receive electrons until there are no more positive ions. The "holes" leave the positive plate and move around the circuit to the other plate, receiving the electrons stored there.
Nicely said, Charlie B.
Ed MacLaren's post and diagrams (April 27, 2003 10:26 PM), emphasizes
The positive ion is at the positive output of the generator. This is the first "hole". A neighboring electron leaves the shell of its copper atom and moves to the positive ion, the atom momentarily shy one electron. Now the neighbor has the hole, and away it goes.
Modern physics has advanced far enough to show that a given electron barely moves, and that while hopping back and about in its neighborhood, the effect, when observing a point on the conductor, is as if the electrons are traveling the length of the circuit at near light speed.
Bryan,
A capacitor holds charge and current. Voltage and Amperage. Two different properties. Together, they are energy (capable of work). When connected to a complete circuit, the positive ions collected on one plate of the capacitor receive electrons until there are no more positive ions. The "holes" leave the positive plate and move around the circuit to the other plate, receiving the electrons stored there.
marissa2
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Re: speed of electrons
I have a book that states, A single electron moves rather slowly. It is estimated that a single electron moves at a rate of about 3 inches per hour at one ampere of current flow.
I have a book that states, A single electron moves rather slowly. It is estimated that a single electron moves at a rate of about 3 inches per hour at one ampere of current flow.
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Re: speed of electrons
Let me throw a curve here, and see if it helps. Consider normal table salt. It is composed of equal numbers of Sodium and Chlorine atoms. Dissolve it in water, and you can observe that each Sodium atom will have given up one of its electrons (leaving it with a net positive charge) to a Chlorine atom (leaving it with a net negative charge) Now perform some chemical magic that separates the mixture into two glasses of fluid: one containing the positively charged Sodium atoms dissolved in water, the other containing the negatively charged Chlorine atoms dissolved in water. Now, just before you pour the first glass into your kitchen sink, put a clamp-on ammeter around the drain pipe. The ammeter will not know that it is around a pipe, and not a wire. It will only observe that positively charged ?stuff? is moving within its sensor range, and it will report to you that there is current. But will it be telling the truth? Can what it is observing really be called ?current?? YES! ABSOLUTELY! The motion of a net positive charge (or negative, if you pour the second glass into the kitchen sink) is the definition of ?current.?
So, what do you think? Clearer? Muddier?
Close, but not quite right. Charge is a property of electrons and protons, and cannot be separated from either. If an electron moves, it brings its charge along with it. Current is the net movement of charge past a given point in space. As we normally deal with current, the motion is that of electrons, and the ?point in space? can be any point along the wire (i.e., the point at which we place our clamp-on ammeter). Charge and energy are independent concepts.
Let me throw a curve here, and see if it helps. Consider normal table salt. It is composed of equal numbers of Sodium and Chlorine atoms. Dissolve it in water, and you can observe that each Sodium atom will have given up one of its electrons (leaving it with a net positive charge) to a Chlorine atom (leaving it with a net negative charge) Now perform some chemical magic that separates the mixture into two glasses of fluid: one containing the positively charged Sodium atoms dissolved in water, the other containing the negatively charged Chlorine atoms dissolved in water. Now, just before you pour the first glass into your kitchen sink, put a clamp-on ammeter around the drain pipe. The ammeter will not know that it is around a pipe, and not a wire. It will only observe that positively charged ?stuff? is moving within its sensor range, and it will report to you that there is current. But will it be telling the truth? Can what it is observing really be called ?current?? YES! ABSOLUTELY! The motion of a net positive charge (or negative, if you pour the second glass into the kitchen sink) is the definition of ?current.?
So, what do you think? Clearer? Muddier?
bphgravity
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Re: speed of electrons
So, if you are saying that electrical current and electrical charge is one in the same, and that this all take place with electrons, then how do you explain shock and electrocution? What about electrolyte in a battery. Do you think electrons are actually flowing through a persons body? What about the electrical current of the brain? More traveling electrons? And how do you explain that the energy is in one direction from source to load, but the electrons are vibrating back and forth due to the AC cycle? If they are the same, wouldn't the charge flow back and forth? When a person speaks, does the air molecules speed to another persons ear at the speed of sound or does the sound wave? The air does not move hardly at all, but the sound wave does. The air (electron) facilitates the energy action. the sound (charge) is doing the real work. Sorry to be on the other side of the fence on this, but the event of electricity itself is not as simple as electron flow.
So, if you are saying that electrical current and electrical charge is one in the same, and that this all take place with electrons, then how do you explain shock and electrocution? What about electrolyte in a battery. Do you think electrons are actually flowing through a persons body? What about the electrical current of the brain? More traveling electrons? And how do you explain that the energy is in one direction from source to load, but the electrons are vibrating back and forth due to the AC cycle? If they are the same, wouldn't the charge flow back and forth? When a person speaks, does the air molecules speed to another persons ear at the speed of sound or does the sound wave? The air does not move hardly at all, but the sound wave does. The air (electron) facilitates the energy action. the sound (charge) is doing the real work. Sorry to be on the other side of the fence on this, but the event of electricity itself is not as simple as electron flow.
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Re: speed of electrons
That?s a lot to deal with, so I?ll take it one point at a time.
That?s a lot to deal with, so I?ll take it one point at a time.
I?m not, no more than I would say that speed and distance are the same. Speed is ?distance traveled per unit time.? Current is ?charge passing a given point per unit of time.?
No, it takes place with charge. Electrons have charge. So do protons. So do whole atoms that are missing one or more electrons (i.e., ?positive ions,? like Na+). So do whole atoms that have one or more extra electrons (i.e., ?negative ions,? like Cl-). Our profession deals mostly with electrons in motion along wires, but ?current? is any ?charge in motion.?
Excellent questions! The answer (to all three) is that our bodies are mostly water, and the water contains vast great quantities of chemicals. Some of the chemicals are ions in solution (Na+ and Cl- are two of these, but there are a host of others). Electrical current passing through a person?s body is manifested by the physical motion of these ions. The human nerve is not a wire, in that it does not conduct current the way any metal object would (i.e., by the motion of free electrons). The brain, the nervous system, and (in the event of accidental shock) the skin and muscles all conduct current by the motion of charged ions.
More traveling ions.
Energy is transferred from the source, along the hot wire, through the load, along the neutral wire, and back to the source for the positive half of the AC cycle. Electrons are not vibrating back and forth during this half cycle, they are moving in that one direction. For the negative half of the AC cycle, electrons are moving in the opposite direction, and energy is transferred from the source, along the neutral wire, through the load, along the hot wire, and back to the source
The difference here is that any one air molecule does not move until is it physically pushed by (i.e., by direct physical contact with) its neighbor molecule. Conversely, all electrons in a wire feel the same force from the same voltage source at the same time. The battery (or AC generator, or transformer, etc.) pushes all free electrons along the entire length of the wire at the same moment. Any one electron does not move because its neighbor pushes it; they all move because the same source is pushing them all. Ohm?s Law works because a higher voltage means all electrons feel a larger push, and therefore more of them are set into motion. Each electron moves from atom to atom at the speed of light, but since more of them are in motion, more of them will pass a given point in a given period of time, and thus we have more current.
I agree with you there.
Re: speed of electrons
I've got my own twisted theory about a capacitor and its charge.
I think the capacitor is like a battery Carbon, lead acid Ect. in the way it stores electricity.It is a chemical action and the chemicals changing from one state to another and in doing so produce an electrical flow or charge.
I think when you put a charge on a capacitor it changes makeup of the dielectric insulation and maybe the composition of the plates.
And when you put the series circuit together by putting a load on it or shorting it it causes a flow of electricity and in doing so changes the plates and chemicals back to the way they where before it was charged.
I have no imformation to back this so if I'm wrong please don't jumpdown my throat.
Ronald
I've got my own twisted theory about a capacitor and its charge.
I think the capacitor is like a battery Carbon, lead acid Ect. in the way it stores electricity.It is a chemical action and the chemicals changing from one state to another and in doing so produce an electrical flow or charge.
I think when you put a charge on a capacitor it changes makeup of the dielectric insulation and maybe the composition of the plates.
And when you put the series circuit together by putting a load on it or shorting it it causes a flow of electricity and in doing so changes the plates and chemicals back to the way they where before it was charged.
I have no imformation to back this so if I'm wrong please don't jumpdown my throat.
Ronald
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Re: speed of electrons
It?s not a bad guess, Ronald, but I?m afraid that it doesn?t account for the capacitors that have nothing but air, or even a vacuum, between the plates. Actually, the truth is simpler and easier to understand.
The parallel plates are made of metal. So there will be permanently fixed positive charges (protons) in the middle of each atom of metal, and negative charges (electrons) spinning around the outside. Some of the electrons are free to move, if they are given a push (by a voltage source). When the capacitor has no power applied, the net sum of the negatives equals the positives, so that each of the two parallel plates has a balanced charge.
Now start applying a current. Let?s talk DC first. Using a battery or other DC voltage source, start pushing electrons down the wire toward one of the two plates. The electrons cannot jump through the gap to the second plate, so they start to build up on the first plate. Now imagine yourself as being a ?free-to-move electron? on the far plate. A moment ago, everywhere you looked everything was balanced (positive equals negative). But now there is a build-up of negatives just across the gap. Remember the ?opposites attract, likes repel? rule? You have a negative charge, and you see a build up of negative charges nearby, so you will feel a force that pushes you away from the plate, and out the wire on the opposite side of the capacitor. That is how current ?passes through? a capacitor. No electron that enters one wire and goes to one plate ever makes it out of the capacitor. Rather, it pushes a different electron away from the far plate, and that other electron continues the current flow out the other wire.
The final DC-related question is, ?Why does the current stop flowing?? As the electrons on the far plate are pushed away, they leave behind (on the far plate) a net positive charge. As this process keeps going on, as more negatives build up on the near plate and more ?absences of negatives? (i.e., net positives) build up on the far plate, an electric field builds up between the plates. This field creates a voltage that is opposite in direction to the voltage source that started current flowing in the first place. Eventually, the voltage built up by the capacitor itself matches the voltage of the battery, and no more current can flow. Why not? Because of Ohm?s Law: V = I * R. But in this case, you have to include the total voltage, which equals the battery voltage minus the capacitor?s built up voltage. When the two are equal, the total voltage is zero, and therefore the current I = 0.
Last point: What?s different about AC? The AC source pushes electrons down one wire towards the capacitor on one half of the cycle, and pushes electrons down the other wire into the other side of the capacitor on the other half cycle. So long as the source voltage keeps changing (up and down, positive and negative), there will be a continuous current flow (which also keeps changing up and down, positive and negative).
It?s not a bad guess, Ronald, but I?m afraid that it doesn?t account for the capacitors that have nothing but air, or even a vacuum, between the plates. Actually, the truth is simpler and easier to understand.
The parallel plates are made of metal. So there will be permanently fixed positive charges (protons) in the middle of each atom of metal, and negative charges (electrons) spinning around the outside. Some of the electrons are free to move, if they are given a push (by a voltage source). When the capacitor has no power applied, the net sum of the negatives equals the positives, so that each of the two parallel plates has a balanced charge.
Now start applying a current. Let?s talk DC first. Using a battery or other DC voltage source, start pushing electrons down the wire toward one of the two plates. The electrons cannot jump through the gap to the second plate, so they start to build up on the first plate. Now imagine yourself as being a ?free-to-move electron? on the far plate. A moment ago, everywhere you looked everything was balanced (positive equals negative). But now there is a build-up of negatives just across the gap. Remember the ?opposites attract, likes repel? rule? You have a negative charge, and you see a build up of negative charges nearby, so you will feel a force that pushes you away from the plate, and out the wire on the opposite side of the capacitor. That is how current ?passes through? a capacitor. No electron that enters one wire and goes to one plate ever makes it out of the capacitor. Rather, it pushes a different electron away from the far plate, and that other electron continues the current flow out the other wire.
The final DC-related question is, ?Why does the current stop flowing?? As the electrons on the far plate are pushed away, they leave behind (on the far plate) a net positive charge. As this process keeps going on, as more negatives build up on the near plate and more ?absences of negatives? (i.e., net positives) build up on the far plate, an electric field builds up between the plates. This field creates a voltage that is opposite in direction to the voltage source that started current flowing in the first place. Eventually, the voltage built up by the capacitor itself matches the voltage of the battery, and no more current can flow. Why not? Because of Ohm?s Law: V = I * R. But in this case, you have to include the total voltage, which equals the battery voltage minus the capacitor?s built up voltage. When the two are equal, the total voltage is zero, and therefore the current I = 0.
Last point: What?s different about AC? The AC source pushes electrons down one wire towards the capacitor on one half of the cycle, and pushes electrons down the other wire into the other side of the capacitor on the other half cycle. So long as the source voltage keeps changing (up and down, positive and negative), there will be a continuous current flow (which also keeps changing up and down, positive and negative).
Re: speed of electrons
Charlie
I can't argue because like I said my theory is just a guess.
When we talk about a vacuum we are not really sure there is nothing there.Just nothing we can detect.
And in this case maybe the plates change there composition.Has this ever been investigated?
Charlie when I was in electrical trade school we where taught that electricity didn't flow through a capacitor it just charges and discharges? We use this property in electronic timing circuits with DC applied to a capacitor it charges to the applied voltage and stops.With ac it discharges when the voltage changes polarity.Electricity doesn't flow through a capacitor just back and forth and appears to flow through it.
In a good quality capacitor the resistance of the dielectric is in the megohms and what about the vacuum condenser you mention?
Ronald :roll:
[ April 29, 2003, 05:14 PM: Message edited by: ronaldrc ]
Charlie
I can't argue because like I said my theory is just a guess.
When we talk about a vacuum we are not really sure there is nothing there.Just nothing we can detect.
And in this case maybe the plates change there composition.Has this ever been investigated?
Charlie when I was in electrical trade school we where taught that electricity didn't flow through a capacitor it just charges and discharges? We use this property in electronic timing circuits with DC applied to a capacitor it charges to the applied voltage and stops.With ac it discharges when the voltage changes polarity.Electricity doesn't flow through a capacitor just back and forth and appears to flow through it.
In a good quality capacitor the resistance of the dielectric is in the megohms and what about the vacuum condenser you mention?
Ronald :roll:
[ April 29, 2003, 05:14 PM: Message edited by: ronaldrc ]
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Re: speed of electrons
They don?t change their CHEMICAL composition. The aluminum doesn?t change to copper, the solid material doesn?t change to liquid, and there is no change to the way that the metal atoms are arranged amongst each other. But electrons do build up on one plate and are driven from the other. If you count that as ?changing composition,? then I?d agree.
Exactly so. Well put!
Never dealt with one myself. But the resistance of a true vacuum is infinite.
Re: speed of electrons
Charlie please don't get upset with me you explained very good in your post that current doesn't flow through the cap. but in one sentence you said thats the way current flows through a capacitor we know you meant appears to flow through. I just wanted to stress that current doesn't flow through a capacitor.For the ones just learning.
Ronald
Charlie please don't get upset with me you explained very good in your post that current doesn't flow through the cap. but in one sentence you said thats the way current flows through a capacitor we know you meant appears to flow through. I just wanted to stress that current doesn't flow through a capacitor.For the ones just learning.
Ronald
Ed MacLaren
Senior Member
Re: speed of electrons
What is really interesting about a capacitor is how it causes an alternating current to lead the line voltage.
This is exactly opposite to the effect of a coil, which causes the current to lag the voltage.
Ed
What is really interesting about a capacitor is how it causes an alternating current to lead the line voltage.
This is exactly opposite to the effect of a coil, which causes the current to lag the voltage.
Ed
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