Yes you would have alternating current, but not referenced to ground, referenced to 1/2 the battery voltage. the current reverses direction in reference to the the voltage it alternates around. Not ground, unless the reference also happens to be ground. To reversing direction is a relative thing.
It makes all the difference in the world depending what your studying. For example it would be impossible to understand how a diode can convert AC to DC if one doesn't understand the difference between alternating current and direct current. The fact that AC reverses direction plays in important part in understanding half and full wave rectifiers.
I am try to understand the flow of different types current in tube amplifiers.
AC doesn't mean "reverses direction," it means "changes with time." The former is a special case of the latter.
According to these source it does.
"an electric current that reverses direction sinusoidally; "In the US most household current is AC at 60 cycles per second"
"In alternating current (AC, also ac) the movement (or flow) of electric charge periodically reverses direction. An electric charge would for instance move forward, then backward, then forward, then backward, over and over again. ..."
en.wikipedia.org/wiki/Alternating_current
"an electric current in which the direction of flow of the electrons reverses periodically having an average of zero, with positive and negative values (with a frequency of 50 Hz in Europe, 60 Hz in the US, 400 Hz for airport lighting, and some others); especially such a current produced by a ..."
en.wiktionary.org/wiki/alternating_current
"(ac)- Current produced by an alternator. Requires converting to direct current by a rectifier for charging purposes."
motorbike-search-engine.co.uk/motorcycle-glossary.php
"Flow of electricity that constantly changes direction between positive and negative sides. Almost all power produced by electric utilities in the United States moves in current that shifts direction at a rate of 60 times per second."
Energy Terms Glossary A
"A polarity of current which is reversed periodically, creating a regular system of sine waves. Commonly known as AC current."
FIRE DICTIONARY
"A current whose polarity alternates from positive to negative over time. Alteration rate is measured in cycles per second – or Hertz (Hz)."
hccii.com/products/technical-information/definition-of-terms/default.asp
"Alternating current is a current that flows alternately in one direction and then in the reverse direction. In North America, the standard for alternating current changes direction 60 times each second - known as a frequency of 60 hertz."
albertaelectricityfuture.com/alberta/
Half, full, any wave rectifier consists of diodes. Diode's resistance depends on potential between it's contacts, but it does not depend on potential in respect to any other thing like ground, roof, mountain, etc... You should start thinking of difference of potentials, rather than of potential itself and it's polarity. Do you know how big is Earth's charge in respect to the Universe? If it is big, how at all would be alternate current possible on the Earth, if it is only and only oscillates (according to your understanding how I understand it), around some absolute zero volt reference?
All of those cites are examples of AC. But there's more to it than just AC mains power. If you just get the concept that any signal consists of the sum of a time-invariant component plus a time varying component, and that the former component is DC and the latter component is AC, you're home free.
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Some thoughts on 'current'
when thinking about how devices, like tubes, actually work it's common to consider the physical nature of them. For tubes we understand their workings as the movement of electrons. These electrons are generated primarily at the Cathode through heating and they can be induced to move to the Anode (plate) by generating an electric field in the space between. Because we don't aim to generate electrons at the Anode by heating it wouldn't normally be possible to operate the tube so that the electrons flow could be reversed.
Through a quirk of history & convention, electrons are deemed to be negatively charged. Which means that when electrons flow from Cathode to Anode it is a flow of negative charge. However it is an agreed convention that current is defined as a flow of positive charge. You might say that a negative current flows from Cathode to Anode but it's more common to say there is a positive current flowing in the opposite direction, from Anode to Cathode. So even though there is no physical entity flowing from the Anode to Cathode, we say that this is the direction of the current flow.
Another example where current flow does not correspond to the movement of physical items is in the dielectric of a capacitor. The dielectric of a perfect capacitor allows no charged particles to flow through it, yet in terms of circuit analysis current does flow through a capacitor.
So when thinking about how tubes work, you need to stick with electrons at first, then you can more easily relate their workings to the physical reality of what's going on.
The electron flow from Cathode to Anode depends on the electric field between them. This electric field can be controlled by changing the voltage between Cathode and Anode (as you can guess, this is a diode). It's possible to change the electric field in the space between the Cathode and Anode by adding another conductor and applying a voltage between it and the Cathode. We don't want this conductor to block the flow of electrons so it's made of fine wires or mesh to form a grid. By applying a voltage between the grid and the Cathode the flow of electrons can be be increased and decreased relative to the steady flow that exists when the grid is not present. Note that you are not simply applying a signal to the grid, it must be a signal that is applied between grid and Cathode.
From this we learn that the triode is a device in which an applied voltage changes the current flowing through it (and in my opinion this is how you should view the operation of all known active devices including FETs, BJTs, JFETs etc.)
when thinking about how devices, like tubes, actually work it's common to consider the physical nature of them. For tubes we understand their workings as the movement of electrons. These electrons are generated primarily at the Cathode through heating and they can be induced to move to the Anode (plate) by generating an electric field in the space between. Because we don't aim to generate electrons at the Anode by heating it wouldn't normally be possible to operate the tube so that the electrons flow could be reversed.
Through a quirk of history & convention, electrons are deemed to be negatively charged. Which means that when electrons flow from Cathode to Anode it is a flow of negative charge. However it is an agreed convention that current is defined as a flow of positive charge. You might say that a negative current flows from Cathode to Anode but it's more common to say there is a positive current flowing in the opposite direction, from Anode to Cathode. So even though there is no physical entity flowing from the Anode to Cathode, we say that this is the direction of the current flow.
Another example where current flow does not correspond to the movement of physical items is in the dielectric of a capacitor. The dielectric of a perfect capacitor allows no charged particles to flow through it, yet in terms of circuit analysis current does flow through a capacitor.
So when thinking about how tubes work, you need to stick with electrons at first, then you can more easily relate their workings to the physical reality of what's going on.
The electron flow from Cathode to Anode depends on the electric field between them. This electric field can be controlled by changing the voltage between Cathode and Anode (as you can guess, this is a diode). It's possible to change the electric field in the space between the Cathode and Anode by adding another conductor and applying a voltage between it and the Cathode. We don't want this conductor to block the flow of electrons so it's made of fine wires or mesh to form a grid. By applying a voltage between the grid and the Cathode the flow of electrons can be be increased and decreased relative to the steady flow that exists when the grid is not present. Note that you are not simply applying a signal to the grid, it must be a signal that is applied between grid and Cathode.
From this we learn that the triode is a device in which an applied voltage changes the current flowing through it (and in my opinion this is how you should view the operation of all known active devices including FETs, BJTs, JFETs etc.)
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I think part of JOW's confusion is the vernacular misapplication of the term "AC" ("Alternating Current"). The current is not alternating in the plate-cathode circuit of a triode; it is varying in accordance with a signal and this variation is often termed the "AC component". However, the term "AC" should not be taken literally here, because that obviously leads to confusion. Also, the signal on the grid is a fuctuating voltage, not an alternating current.
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Yes, the whole thing can be confusing, a lot of history to why things are described the way they are.
It's really a mathematical convenience that we can treat a single varying current as being made up of a steady current flow (dc) and a time varying current flow (ac).
The root of this is the poor correspondence between current flow and physical electron movement.
In the mains wiring of your house the electrons reverse their direction of flow, and the equivalent description of this in terms of current flow makes good sense when it is described as alternating current.
But in a triode the electrons are moving from Cathode to Anode, they don't alternate their direction of movement. When you apply a signal between the grid and Cathode this in turn modulates the electron flow, changing the number of electrons arriving at the Anode from moment to moment. In the physical sense, the electrons do not alternate their direction of flow. So describing this as an AC current flow that alternates again shows that there is not always a direct correspondence between physical movement of the electrons and the conventional description.
It's really a mathematical convenience that we can treat a single varying current as being made up of a steady current flow (dc) and a time varying current flow (ac).
The root of this is the poor correspondence between current flow and physical electron movement.
In the mains wiring of your house the electrons reverse their direction of flow, and the equivalent description of this in terms of current flow makes good sense when it is described as alternating current.
But in a triode the electrons are moving from Cathode to Anode, they don't alternate their direction of movement. When you apply a signal between the grid and Cathode this in turn modulates the electron flow, changing the number of electrons arriving at the Anode from moment to moment. In the physical sense, the electrons do not alternate their direction of flow. So describing this as an AC current flow that alternates again shows that there is not always a direct correspondence between physical movement of the electrons and the conventional description.
I guess the problem is my literal take on the definition of alternating current.
So would it be safe to say that if you take alternating current to mean that the current "electron flow" reverses periodically, Then the current produced from the plate would be oscillating DC?
So would it be safe to say that if you take alternating current to mean that the current "electron flow" reverses periodically, Then the current produced from the plate would be oscillating DC?
Hi Bigun;
have you seen that flow of electrons? How do you know they really exist and flow?
And, what is an electron? Is it a hard corpuscle, or a soft cloud, or an electro-magnetic wave? Which model is true?
have you seen that flow of electrons? How do you know they really exist and flow?
And, what is an electron? Is it a hard corpuscle, or a soft cloud, or an electro-magnetic wave? Which model is true?
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Wavebourn, you are teasing again 🙂
Well, I have to say, I have seen the electrons ! the other night I was using my tube amp, with the nice big Russian 6H5C and on the side of the glass there was a spot with some blue glow. That's the electrons - we all know electrons are blue, you can see them when they jump between wires at high voltage 😀
Of course, for some they are a particle, others a wave. And the craziest one I heard once was that electrons are micro-sized black holes with a photon on the event horizon, frozen in time such that the electric field of the photon creates the electric field we see around an 'electron' and interpret as negative charge. Since black holes allow no information to escape them, all electrons appear as identical.
Well, I have to say, I have seen the electrons ! the other night I was using my tube amp, with the nice big Russian 6H5C and on the side of the glass there was a spot with some blue glow. That's the electrons - we all know electrons are blue, you can see them when they jump between wires at high voltage 😀
Of course, for some they are a particle, others a wave. And the craziest one I heard once was that electrons are micro-sized black holes with a photon on the event horizon, frozen in time such that the electric field of the photon creates the electric field we see around an 'electron' and interpret as negative charge. Since black holes allow no information to escape them, all electrons appear as identical.
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No, the electron flow doesn't reverse, nor the current flow. In a triode the majority of current is always flowing in one direction. The signal is only modulating it. Think of hose pipe with water pouring out of it - you squeeze it and relax and the flow decreases and then increases back to normal. You are able to modulate the flow of water but it always flows out of the pipe. Over a long time the average flow of water is the 'dc' but looking at the increase and decrease of flow you make happen by squeezing the pipe is a fluctuation in the flow rate up and down, this is the 'ac'.
I would refrain from using the expression 'oscillating dc' - it's a kind of oxymoron.
Here is the problem. The definitions below are repeated over and over in many electronics books and sites
"In alternating current (AC, also ac) the movement of electric charge periodically reverses direction. In direct current (DC), the flow of electric charge is only in one direction."
Alternating current - Wikipedia, the free encyclopedia
As explained by people in this forum and the NEETS modules current through a triode can only travel from cathode to plate (one direction). Then current leaving the triode can only be DC. The definition of AC is not fluctuating voltage/current. It's the reversal of current (see above, or any electronics site). If the signal leaving the plate can only travel in one direction, then it meets the definition of DC.
If we take the definition of AC as true how can there be AC leaving the plate?
"In alternating current (AC, also ac) the movement of electric charge periodically reverses direction. In direct current (DC), the flow of electric charge is only in one direction."
Alternating current - Wikipedia, the free encyclopedia
As explained by people in this forum and the NEETS modules current through a triode can only travel from cathode to plate (one direction). Then current leaving the triode can only be DC. The definition of AC is not fluctuating voltage/current. It's the reversal of current (see above, or any electronics site). If the signal leaving the plate can only travel in one direction, then it meets the definition of DC.
If we take the definition of AC as true how can there be AC leaving the plate?
First off, that particular Wikipedia definition is limited to the context of power transmission. By their definition in the particular article you linked to, a square wave is not AC. Really?
Second, what leaves the plate is the voltage equation that I stated several posts back. It consists of a linear sum of a DC component and an AC component.
That means, Wikipedia is good source of opinion of authors, but bad source of information.
I once tried to correct errors and nonsenses in Wikipedia about vacuum tubes, but people who own that b@@lshit called me vandal and returned all back.
I once tried to correct errors and nonsenses in Wikipedia about vacuum tubes, but people who own that b@@lshit called me vandal and returned all back.
your "making" ac from dc. ac from your outlet in your house is in refrance to ground.
your triode cir is in refrance to what u decide. using your example of the pot and batt ....lets say @ 2 volts. by putting the pot in the middle your refrance point is 1 volt......call that ground... turn the pot down and voltage gose +. turn the pot up it gose -. do that 60 times in one second and it 60hz in refrance to ground ...your ground . beucase if u clipped a fluke meter to your pot and a ground rod u wouldent read anything.
if you notice the input of most amps are tied to the ground or there 0v point so it all is together.
the ac signal coming in has its 0v point or ground........tied to your cir 0v or gound. it all has the same point of refrence.
the caps will block dc or 0hz, . after that it lets the "made" ac go through cause i it dosent care what the 0 point is just that it is swinging .
your triode cir is in refrance to what u decide. using your example of the pot and batt ....lets say @ 2 volts. by putting the pot in the middle your refrance point is 1 volt......call that ground... turn the pot down and voltage gose +. turn the pot up it gose -. do that 60 times in one second and it 60hz in refrance to ground ...your ground . beucase if u clipped a fluke meter to your pot and a ground rod u wouldent read anything.
if you notice the input of most amps are tied to the ground or there 0v point so it all is together.
the ac signal coming in has its 0v point or ground........tied to your cir 0v or gound. it all has the same point of refrence.
the caps will block dc or 0hz, . after that it lets the "made" ac go through cause i it dosent care what the 0 point is just that it is swinging .
oh and i cant spell...and the spellcheck dosnt work for this site on my phone sorry
i hope that helps.
no backward current nessary to have ac. just 0 point and up swing and down swing
i hope that helps.
no backward current nessary to have ac. just 0 point and up swing and down swing
Come on guys really! Don't take my word for it look up the definition of alternating current yourself. I provided source and definitions in a previous post. Plenty of sites state the same definitions. So all the definition available are wrong?
To clarify Sy on the article and square waves:
"The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves."
To clarify Sy on the article and square waves:
"The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves."
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