What is the "speed" of electricity?
OK, I know the speed of light in vacuum, and the speed sound in a given medium. But if I had (say) 1km of wire, a BIG battery, light bulb and a switch connected in series (or slightly more technical version thereof). How long after closing the switch would it take for the bulb to light? Doubtless it depends on the voltage? But say with these old transatlantic cables there must be some measureable delay? Just wondered? any thoughts?
Answers:
Actually the individual electrons flowing in the circuit move at slow speeds. Imagin a pipe one foot in diameter full of marbels. If you push one marble into the pipe one marble pops out of the other end. If the marbels are stacked nicely say there are 100 marbles across each marbel had to move 1/100 marble diameters to get one to pop out the other end. electron flow is like that only there are a very great number of conduction sites across the diameter of even a small wire. there is a good discription of the whole thing here-
http://hyperphysics.phy-astr.gsu.edu/hba.
shocking
Lightening fast
same speed as light.....'kin fast
You'd have to ask his dealer.
not sure but the variables are irrelevant I think electricity travels at the speed of light regardless of resistance,temperature,voltage etc. It's a bit like gravity's affect on an object its a constant regardless of weight,mass,size,shape etc
I do not know. but it isn't as fast as light.
SPEED OF "ELECTRICITY"
1996 Bill Beaty
How fast does electricity flow? Well, it depends on what you mean by "electricity." The word Electricity has more than one contradictory meaning, so before we can talk about its flow, we have to decide on which of several "electricities" we really mean. For a discussion of electric current, see below. But for articles about fast-flowing electromagnetic energy, see the FAQ, or this email discussion.
OK, then how about this. When we turn on a flashlight, something called an "electric current" begins to happen. Inside the flashlight bulb, the thin filament-wire gets hot because there is electric current in the metal. This current is a motion of something. How fast does this "something" move? This question can be answered.
The quick answer
Inside the wires, the "something" moves very, very slowly, almost as slowly as the minute hand on a clock. Electric current is like a flow of syrup. Even maple syrup moves too fast, so that's not a good analogy. Electric charges flow as slowly as a river of warm putty. And in AC circuits, it doesn't move forward at all, instead it sits in one place and vibrates. Energy can flow fast in an electric circuit because metals are already filled with this "putty." If you push on one end of a column of putty, the far end moves almost instantly. Energy flows fast, yet an electric current is a very slow flow.
The complicated answer
Within all metals there is a substance which can move. This stuff has several different names: the Sea of Charge, or the Electron Sea, or the Electron Gas, or "charge." We often call it "electricity." Calling it "electricity" can be misleading because charge is not energy, yet many people think that electrical energy is the "electricity." It can be misleading because the Sea of Charge exists within in all metal objects, all the time, even when the metal has not been made into a wire and is not part of an electric device. If the Electron Sea is "electricity," then we must say that all metals are full of electricity. Better to call it by the name "charge-sea," and avoid the misleading word "electricity".
During an electric current, the wire stays still and the sea of charge flows along through it. When the flashlight switch is turned off and the lightbulb goes dark, the charge-sea stops moving forward. Even though it stops moving, the charge-sea is still inside of that wire. If the flashlight is again turned on and two light bulbs are connected in parallel instead of one, the electric current will have twice as large a value, and twice as much light will be created. And most important, the charge-sea of the battery's wires will flow twice as fast. In other words, THE SPEED OF THE CHARGES IS PROPORTIONAL TO THE VALUE OF ELECTRIC CURRENT; small current means low-speed charge flow, large current means high speed. Zero current means the charges have stopped. Note however that an electric current does not have just one speed. Charges speed up when they flow into a thinner wire. The high current in the lightbulb of a big flash-lantern will be much faster than the same current in the conductors in the lantern. Even though an electric current is a very slow flow of charges, we can't know the actual speed of flow unless first we know the *value* (the amperes) of the current in the wires.
If a thin wire is connected in a circuit end to end with a thick wire, it turns out that the charges in the thin wire move faster. This makes sense, it works just like water in rivers. If a huge wide river moves into a narrow channel, the water speeds up. When the channel opens out again downstream, the river slows down again. The flow in a very thin wire will be tend to be fast, even if the value of current is fairly low. This means that we can't know the speed of the flowing charge-sea unless we know how thick the wires are.
If a copper wire is connected into a series circuit with an aluminum wire of the same diameter, the charges in the copper will flow slower. This occurs because there is one movable charge per each atom in the metals, but there are more atoms packed into the copper than into the aluminum, so there is more charge in each bit of copper. When the charge-sea flows into the copper, it gets packed together and slows down. When it flows out into the aluminum, it spreads out a bit and speeds up. This means that we cannot know how fast the charges flow unless we know how dense the charge-sea is within the metal.
The speed of electric current
Since nothing visibly moves when the charge-sea flows, we cannot measure the speed of its flow by eye. Instead we do it by making some assumptions and doing a calculation. Let's say we have an electric current in normal lamp cord connected to bright light bulb. The electric current works out to be a flow of approximatly 3 inches per hour. Very slow!
Here's how I worked out that value. I know:
Bulb power: about 100 watts, about 100V at 1A
Value for electric current: I = 1 ampere
Wire diameter: D = 2/10 cm, radius R=.1cm
Mobile electrons per cc (for copper, if 1 per atom): Q = 8.5*10^+22
Charge per electron: e = 1.6*10^-19
The equation:
cm/sec = ________I_______ = .0023 cm/sec = 8.4 cm/hour
Q * e * R^2 * pi
This is for DC. Chris R. points out that for a particular value of frequency of AC, the "skin effect" can cause the flow of charges in the center of a wire to be reduced while the current on the surface becomes stronger. There are fewer charges flowing, and hence they must flow faster. ("Skin Effect" is stronger at high frequencies and with thick wires. The effect can USUALLY be ignored in thin wires at 60Hz power-line frequencies.)
The size of the wiggle
And about AC. how far do the electrons move as they vibrate back and forth? Well, we know that a one-amp current in 1mm wire is moving at 8.4cm per hour, so in one second it moves:
8.4cm / 3600sec = .00233 cm per second
And in 1/60 of a second it will travel back and forth by
.00233cm/sec / (1/60) = .0000389cm, or around .00002"
This simple calculation is for a square wave. For a sine wave we'd integrate the velocity to determine the width of electron travel.
So for a typical AC current in a typical lamp cord, the electrons don't actually "flow," instead they vibrate back and forth by about a hundred-thousandth of an inch.
The width of one Coulomb
On thinking along these lines I notice something interesting: in copper, one coulomb of movable electrons has a certain size! There are about 13,000 coulombs of free electrons per cubic centimeter of copper.
8.5*10^+22 elect/cc * 1.6*10^-19 coul./elect = 13600 Coul./cc
Therefore one coulomb would form a cube approximately 0.4mm across.
1/(13600cc^(1/3)) = 0.042 cm
HA! A coulomb in copper is about the size of a grain of sand! We can now discuss electric current within wires as if it were cc per second of fluid flow inside of small hoses. If an Ampere is one coulomb per second, we're REALLY saying that an Ampere is "one saltgrain-sized blob, moving each second, squeezing itself into whatever sized wire." So, for the usual sizes of wires in electric circuitry, if we deliver one salt-grain per second (one amp,) that's a very slow flow. In 16-gauge wire the saltgrain blobs would resemble very thin stacked pancakes. In 30-gauge wire the saltgrains would be almost undistorted, and charges would move at about 0.4 mm/sec during a 1-amp current.
------------------------------.
One thing's not certain in the above calculations: the charge density for copper. My above value for Q assumes that each copper atom donates a single movable electron. The email from the person below points out that this might not be true. For example, if only one conduction electron in ten are movable and the rest are "compensated" and frozen, then the speed of the charge flow will be ten times greater than 8.4cm/hour.
One final point. Electrons in metals do not hold still. They wiggle around constantly even when there is zero electric current. However, this movement is not really a flow, it is more like a vibration, or like a high-speed wandering movement. How should we picture this? Well, we can speak of wind, and water flow. yet a similar type of motion is found in the atoms of all normal liquids and gases. Even when the wind is less than one MPH, the air molecules are zooming around at hundreds of MPH. Even when there is no wind at all, the air molecules still wiggle around at the same high speeds. We usually ignore this when discussing wind. We call it "thermal vibration," and we see it as a separate issue. Therefore we should do the same with circuitry: the electric current is akin to wind, while the high speed wandering motions of individual electrons is akin to thermal vibrations of the air. In the above article I concentrate on the slow "electron wind" which is measured by electric current meters, and I ignore the electrons' high speed "thermal vibration."
Apart from voltage it also depends on the material of the cable as well as the insulation. It also differs wether you use ac or dc. All these things depend on the use. The actual speed varies from few meters per second upwards.
It's the same as the speed of light, 186,282.397 miles per second.or 299,792,458 meters per second.
It's "speed" is the same regardless of cable length, battery size, voltage etc.
It's a physical constant.
Ah some one who doesn't know his esoteric theories I see.
electricity is presumed to be a flow of electrons through a circuit.
however this 'flow' shows wave and particle properties. The driving force is the potential difference between the power source and the light bulb. Although the electrons are presumed to be passed from atom to atom along the copper wire. However because of the fact that this 'exchange' is presumed to flow along the circuit but the pd remains constant then we move into the realms of quantum physics where all these transfers take place at the same time. So it is generally presumed to be at the speed of light but may in fact be instantaneous. Cant go any deeper than that I only went to elementary school. lol
You need to get down the pub, immediately
No....stop looking at this, I mean now!!
Hmmm.
Everyone who said "speed of light" is wrong.
Electrons have mass, and they move _much_ slower than light-speed.
It`s very, very fast.
There are two things to consider.
1. The actual drift of the electrons. Say for an electron to flow out of a battery and into the filament of a light is slow.
2. the voltage, signal is very fast. The voltage travels down the wire to the light very fast so the light comes on very fast. This can vary with material. Integrated circuits are starting to use copper since it will speed of the circuits. (It likes to diffuse into the transistors destroying them so barriers are needed)
Might think of this as the electrons bump into each other and the next one until there is flow at the filament,(or something) so the time between switching and seeing something come "on" is very fast.
Generally speaking electricity is travelling at speed of light.
When the electricity is in a different medium, then the speed is different.
For example, on a FR4 PCB, the electricity travel at 6 inch every nano seconds. That means it travel 500 million feet per second.
The speed of electricity is essentially that of light. The simplest analogy I can give you is the one I was taught about a hundred years ago. Any conductor of electricity has many free electrons waiting to be dislodged from its atoms. They exist along the entire length of the conductor. Now think of a wire, any conductor of electricity as being analogous to a hollow tube filled with ping pong balls from one end to the other, and think of the ping pong balls as electrons.
The tube, like the wire is filled. If you push another ping pong ball into the tube at one end, a ping pong ball is instantaneously expelled from the other end of the tube. Similarly, when an electrical pressure (voltage) is applied to a conductor in a closed circuit, the first electron from the voltage source entering the wire, causes an electron to instantaneously exit the wire at the opposite end of the circuit.
As far as delay due to distance is concerned, it can be calculated by the speed of light (186,000mi/sec) divided into the length of the circuit (wire, cable).
300,000 kilometers per second
186,000 miles per second
You will get a voltage drop, loss of power (watts) over a long distance.
What I was told a battery may have a delay if in low temperature, yet we are talking 1/1000 of a second.
I'm not a hundred percent sure on AC current, as that would work on hertz, if you drop the hertz rate some thing might change.
Hope that helps.
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Answers:
Actually the individual electrons flowing in the circuit move at slow speeds. Imagin a pipe one foot in diameter full of marbels. If you push one marble into the pipe one marble pops out of the other end. If the marbels are stacked nicely say there are 100 marbles across each marbel had to move 1/100 marble diameters to get one to pop out the other end. electron flow is like that only there are a very great number of conduction sites across the diameter of even a small wire. there is a good discription of the whole thing here-
http://hyperphysics.phy-astr.gsu.edu/hba.
shocking
Lightening fast
same speed as light.....'kin fast
You'd have to ask his dealer.
not sure but the variables are irrelevant I think electricity travels at the speed of light regardless of resistance,temperature,voltage etc. It's a bit like gravity's affect on an object its a constant regardless of weight,mass,size,shape etc
I do not know. but it isn't as fast as light.
SPEED OF "ELECTRICITY"
1996 Bill Beaty
How fast does electricity flow? Well, it depends on what you mean by "electricity." The word Electricity has more than one contradictory meaning, so before we can talk about its flow, we have to decide on which of several "electricities" we really mean. For a discussion of electric current, see below. But for articles about fast-flowing electromagnetic energy, see the FAQ, or this email discussion.
OK, then how about this. When we turn on a flashlight, something called an "electric current" begins to happen. Inside the flashlight bulb, the thin filament-wire gets hot because there is electric current in the metal. This current is a motion of something. How fast does this "something" move? This question can be answered.
The quick answer
Inside the wires, the "something" moves very, very slowly, almost as slowly as the minute hand on a clock. Electric current is like a flow of syrup. Even maple syrup moves too fast, so that's not a good analogy. Electric charges flow as slowly as a river of warm putty. And in AC circuits, it doesn't move forward at all, instead it sits in one place and vibrates. Energy can flow fast in an electric circuit because metals are already filled with this "putty." If you push on one end of a column of putty, the far end moves almost instantly. Energy flows fast, yet an electric current is a very slow flow.
The complicated answer
Within all metals there is a substance which can move. This stuff has several different names: the Sea of Charge, or the Electron Sea, or the Electron Gas, or "charge." We often call it "electricity." Calling it "electricity" can be misleading because charge is not energy, yet many people think that electrical energy is the "electricity." It can be misleading because the Sea of Charge exists within in all metal objects, all the time, even when the metal has not been made into a wire and is not part of an electric device. If the Electron Sea is "electricity," then we must say that all metals are full of electricity. Better to call it by the name "charge-sea," and avoid the misleading word "electricity".
During an electric current, the wire stays still and the sea of charge flows along through it. When the flashlight switch is turned off and the lightbulb goes dark, the charge-sea stops moving forward. Even though it stops moving, the charge-sea is still inside of that wire. If the flashlight is again turned on and two light bulbs are connected in parallel instead of one, the electric current will have twice as large a value, and twice as much light will be created. And most important, the charge-sea of the battery's wires will flow twice as fast. In other words, THE SPEED OF THE CHARGES IS PROPORTIONAL TO THE VALUE OF ELECTRIC CURRENT; small current means low-speed charge flow, large current means high speed. Zero current means the charges have stopped. Note however that an electric current does not have just one speed. Charges speed up when they flow into a thinner wire. The high current in the lightbulb of a big flash-lantern will be much faster than the same current in the conductors in the lantern. Even though an electric current is a very slow flow of charges, we can't know the actual speed of flow unless first we know the *value* (the amperes) of the current in the wires.
If a thin wire is connected in a circuit end to end with a thick wire, it turns out that the charges in the thin wire move faster. This makes sense, it works just like water in rivers. If a huge wide river moves into a narrow channel, the water speeds up. When the channel opens out again downstream, the river slows down again. The flow in a very thin wire will be tend to be fast, even if the value of current is fairly low. This means that we can't know the speed of the flowing charge-sea unless we know how thick the wires are.
If a copper wire is connected into a series circuit with an aluminum wire of the same diameter, the charges in the copper will flow slower. This occurs because there is one movable charge per each atom in the metals, but there are more atoms packed into the copper than into the aluminum, so there is more charge in each bit of copper. When the charge-sea flows into the copper, it gets packed together and slows down. When it flows out into the aluminum, it spreads out a bit and speeds up. This means that we cannot know how fast the charges flow unless we know how dense the charge-sea is within the metal.
The speed of electric current
Since nothing visibly moves when the charge-sea flows, we cannot measure the speed of its flow by eye. Instead we do it by making some assumptions and doing a calculation. Let's say we have an electric current in normal lamp cord connected to bright light bulb. The electric current works out to be a flow of approximatly 3 inches per hour. Very slow!
Here's how I worked out that value. I know:
Bulb power: about 100 watts, about 100V at 1A
Value for electric current: I = 1 ampere
Wire diameter: D = 2/10 cm, radius R=.1cm
Mobile electrons per cc (for copper, if 1 per atom): Q = 8.5*10^+22
Charge per electron: e = 1.6*10^-19
The equation:
cm/sec = ________I_______ = .0023 cm/sec = 8.4 cm/hour
Q * e * R^2 * pi
This is for DC. Chris R. points out that for a particular value of frequency of AC, the "skin effect" can cause the flow of charges in the center of a wire to be reduced while the current on the surface becomes stronger. There are fewer charges flowing, and hence they must flow faster. ("Skin Effect" is stronger at high frequencies and with thick wires. The effect can USUALLY be ignored in thin wires at 60Hz power-line frequencies.)
The size of the wiggle
And about AC. how far do the electrons move as they vibrate back and forth? Well, we know that a one-amp current in 1mm wire is moving at 8.4cm per hour, so in one second it moves:
8.4cm / 3600sec = .00233 cm per second
And in 1/60 of a second it will travel back and forth by
.00233cm/sec / (1/60) = .0000389cm, or around .00002"
This simple calculation is for a square wave. For a sine wave we'd integrate the velocity to determine the width of electron travel.
So for a typical AC current in a typical lamp cord, the electrons don't actually "flow," instead they vibrate back and forth by about a hundred-thousandth of an inch.
The width of one Coulomb
On thinking along these lines I notice something interesting: in copper, one coulomb of movable electrons has a certain size! There are about 13,000 coulombs of free electrons per cubic centimeter of copper.
8.5*10^+22 elect/cc * 1.6*10^-19 coul./elect = 13600 Coul./cc
Therefore one coulomb would form a cube approximately 0.4mm across.
1/(13600cc^(1/3)) = 0.042 cm
HA! A coulomb in copper is about the size of a grain of sand! We can now discuss electric current within wires as if it were cc per second of fluid flow inside of small hoses. If an Ampere is one coulomb per second, we're REALLY saying that an Ampere is "one saltgrain-sized blob, moving each second, squeezing itself into whatever sized wire." So, for the usual sizes of wires in electric circuitry, if we deliver one salt-grain per second (one amp,) that's a very slow flow. In 16-gauge wire the saltgrain blobs would resemble very thin stacked pancakes. In 30-gauge wire the saltgrains would be almost undistorted, and charges would move at about 0.4 mm/sec during a 1-amp current.
------------------------------.
One thing's not certain in the above calculations: the charge density for copper. My above value for Q assumes that each copper atom donates a single movable electron. The email from the person below points out that this might not be true. For example, if only one conduction electron in ten are movable and the rest are "compensated" and frozen, then the speed of the charge flow will be ten times greater than 8.4cm/hour.
One final point. Electrons in metals do not hold still. They wiggle around constantly even when there is zero electric current. However, this movement is not really a flow, it is more like a vibration, or like a high-speed wandering movement. How should we picture this? Well, we can speak of wind, and water flow. yet a similar type of motion is found in the atoms of all normal liquids and gases. Even when the wind is less than one MPH, the air molecules are zooming around at hundreds of MPH. Even when there is no wind at all, the air molecules still wiggle around at the same high speeds. We usually ignore this when discussing wind. We call it "thermal vibration," and we see it as a separate issue. Therefore we should do the same with circuitry: the electric current is akin to wind, while the high speed wandering motions of individual electrons is akin to thermal vibrations of the air. In the above article I concentrate on the slow "electron wind" which is measured by electric current meters, and I ignore the electrons' high speed "thermal vibration."
Apart from voltage it also depends on the material of the cable as well as the insulation. It also differs wether you use ac or dc. All these things depend on the use. The actual speed varies from few meters per second upwards.
It's the same as the speed of light, 186,282.397 miles per second.or 299,792,458 meters per second.
It's "speed" is the same regardless of cable length, battery size, voltage etc.
It's a physical constant.
Ah some one who doesn't know his esoteric theories I see.
electricity is presumed to be a flow of electrons through a circuit.
however this 'flow' shows wave and particle properties. The driving force is the potential difference between the power source and the light bulb. Although the electrons are presumed to be passed from atom to atom along the copper wire. However because of the fact that this 'exchange' is presumed to flow along the circuit but the pd remains constant then we move into the realms of quantum physics where all these transfers take place at the same time. So it is generally presumed to be at the speed of light but may in fact be instantaneous. Cant go any deeper than that I only went to elementary school. lol
You need to get down the pub, immediately
No....stop looking at this, I mean now!!
Hmmm.
Everyone who said "speed of light" is wrong.
Electrons have mass, and they move _much_ slower than light-speed.
It`s very, very fast.
There are two things to consider.
1. The actual drift of the electrons. Say for an electron to flow out of a battery and into the filament of a light is slow.
2. the voltage, signal is very fast. The voltage travels down the wire to the light very fast so the light comes on very fast. This can vary with material. Integrated circuits are starting to use copper since it will speed of the circuits. (It likes to diffuse into the transistors destroying them so barriers are needed)
Might think of this as the electrons bump into each other and the next one until there is flow at the filament,(or something) so the time between switching and seeing something come "on" is very fast.
Generally speaking electricity is travelling at speed of light.
When the electricity is in a different medium, then the speed is different.
For example, on a FR4 PCB, the electricity travel at 6 inch every nano seconds. That means it travel 500 million feet per second.
The speed of electricity is essentially that of light. The simplest analogy I can give you is the one I was taught about a hundred years ago. Any conductor of electricity has many free electrons waiting to be dislodged from its atoms. They exist along the entire length of the conductor. Now think of a wire, any conductor of electricity as being analogous to a hollow tube filled with ping pong balls from one end to the other, and think of the ping pong balls as electrons.
The tube, like the wire is filled. If you push another ping pong ball into the tube at one end, a ping pong ball is instantaneously expelled from the other end of the tube. Similarly, when an electrical pressure (voltage) is applied to a conductor in a closed circuit, the first electron from the voltage source entering the wire, causes an electron to instantaneously exit the wire at the opposite end of the circuit.
As far as delay due to distance is concerned, it can be calculated by the speed of light (186,000mi/sec) divided into the length of the circuit (wire, cable).
300,000 kilometers per second
186,000 miles per second
You will get a voltage drop, loss of power (watts) over a long distance.
What I was told a battery may have a delay if in low temperature, yet we are talking 1/1000 of a second.
I'm not a hundred percent sure on AC current, as that would work on hertz, if you drop the hertz rate some thing might change.
Hope that helps.
The answers post by the user, for information only, UKQnA.com does not guarantee the right.