strong current / weak current

bloomiegirl

Senior Member
US English
In the domain of electronics (semiconductors), what is meant by "strong current" and "weak current"? I'm no scientist, but even I can tell from the following sentence that it's not "high voltage" and "low voltage":

"The result of this is that breakdown can occur at a lower voltage in the case of a strong current than in the case of a weak current."​

Of course you're wondering what "this" is. Again, I'm no scientist, so here's the website where I found this. It's very dense, at least for me.

Any help is appreciated, but I think this is a question for the techies.

Thank you in advance.

Edit: Also, are strong/weak current different from high/low current? (Perhaps these last two are the same as high/low voltage? But I'm just guessing.) And again, thank you in advcance!
 
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  • liliput

    Senior Member
    U.K. English
    Voltage is the difference in electrical potential between two points and is measured in Volts.

    Current is the flow of electrons, measured in Amps. Presumably if there is a slow flow-rate of electrons then you have a weak current.

    Voltage = Current x Resistance

    Wattage (Power) = Voltage x Current
     
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    panjandrum

    Lapsed Moderator
    English-Ireland (top end)
    This is a rather peculiar and esoteric world.
    My initial response, as a one-time electronic engineer, was that there is no such thing as a strong current or a weak current.
    However, from reading the article, these terms seem to be used to distinguish between an electric current that flows through a relatively small area of the semiconductor (strong current) and the same current flowing through a larger area (weak current). The source also refers to "an increase in the current density".
    It is surprisingly found that this leads to an increase in the breakdown voltage at strong currents and thus to an increase in the SOAR. [...] In a configuration in which the source extends around the tips of the drain fingers, an increase in the current density will occur at the areas of the drain fingers owing to current convergence. An intensification of the electric field will occur there more readily owing to the Kirk effect than in locations having a uniform current distribution. The result of this is that breakdown can occur at a lower voltage in the case of a strong current than in the case of a weak current.
     

    bloomiegirl

    Senior Member
    US English
    Thank you, Liliput, these formulas are quite clear.

    And thank you, Panjandrum, for wending through the technical wording and pointing out the importance of the density of electrons.

    So would it be correct to say that the terms "strong/weak current" are equivalent to "high/low current"? From the same article cited above:
    "The result of this is that, given a certain high current value, the device will be more prone to breakdown (possibly accompanied by irreparable damage) than at low current values."​
    I think this is right, but I'm a babe in the electronic woods!

    Thank you again Liliput and Panjandrum!
     

    Monkey F B I

    Senior Member
    English - USA
    Thank you, Liliput, these formulas are quite clear.

    And thank you, Panjandrum, for wending through the technical wording and pointing out the importance of the density of electrons.

    So would it be correct to say that the terms "strong/weak current" are equivalent to "high/low current"? From the same article cited above:
    "The result of this is that, given a certain high current value, the device will be more prone to breakdown (possibly accompanied by irreparable damage) than at low current values."​
    I think this is right, but I'm a babe in the electronic woods!

    Thank you again Liliput and Panjandrum!

    I suppose it would, but you don't hear "high/low current" very much. I suppose the current values would be the amperage, so indeed, a low current value would be a weak current and a high current value would be a strong current.
     

    bloomiegirl

    Senior Member
    US English
    The quote refers to high and low values rather than high or low currents.
    Yes, that's true, Liliput... in this case. Sorry, I tried to take a shortcut by referring to the already-cited article. (Oops.) But there are many other patents that refer to high/low current without any other qualifier -- for instance this one entitled "High Current and Low Current Electrical Busway Systems having Compatible Bus Plug."

    I suppose it would, but you don't hear "high/low current" very much. I suppose the current values would be the amperage, so indeed, a low current value would be a weak current and a high current value would be a strong current.
    Thank you, Monkey FBI. That's what I was thinking too. Does this sound right to those who know?

    Thanks again!
     
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    panjandrum

    Lapsed Moderator
    English-Ireland (top end)
    There is a great deal of confusion here.

    Let me try to give a different illustration based on the information in the article referred to earlier.

    Suppose you have a very thick piece of wire with a very large cross section and you pass a current of 5 Amps through it.
    Suppose you also have a thin piece of wire with a small cross section and you pass a current of 5 Amps through it.

    By the definition used in the article, the current passing through the wire with the large cross-section is a weak current; the current passing through the wire with the small cross-section is a strong current.

    Alternatively, think of a river.
    Suppose the river has a very, very wide section followed by a very, very narrow section.
    The same quantity of water flows through the wide section and the narrow section.
    But in the wide section there is a weak current, in the narrow section there is a strong current.

    The river analogy is poor, but might convey the sense more clearly.
     

    bloomiegirl

    Senior Member
    US English
    [...]
    Suppose you have a very thick piece of wire with a very large cross section and you pass a current of 5 Amps through it.
    Suppose you also have a thin piece of wire with a small cross section and you pass a current of 5 Amps through it.

    By the definition used in the article, the current passing through the wire with the large cross-section is a weak current; the current passing through the wire with the small cross-section is a strong current.
    [...]

    Ah! I think I understand now: strong/weak current is based on relative density...
    ...but high/low current and high/low voltage are based on the formulas posted by Liliput.

    If this is correct, then I think we're done. Thanks to everyone! :D

    And, Panjandrum, I really like the river analogy, since the flow of water is apparent to the casual observer (like me).
     
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    Monkey F B I

    Senior Member
    English - USA
    Ah! I think I understand now strong/weak current is based on relative density...
    ...but
    -- high/low current or amps is based on watts/volts (or volts/resistance) and
    -- high/low voltage is based on watts/amps (or amps x resistance).

    If this is correct, then I think we're done. Thanks to everyone! :D

    That is correct. The formulas I learned for those were...

    V=IR (voltage = current times resistance...or current = voltage / resistance)

    I think V=IR is a pretty easy way to remember this. It just sticks for some reason.
     

    bloomiegirl

    Senior Member
    US English
    Thank you Monkey... Glad I copied your formulas properly... And yes, I like V=IR; I can remember that!

    As you can see I edited my post to simplify it and emphasize the relative nature of strong/weak current, though I'm not sure if "relative density" is the way to phrase it. But I think I understand that 5 amps can be either strong or weak current, depending on the breadth (e.g. diameter) of the pathway.

    Edit: Wow, I love the WordReference forum! :cool:
     
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    nikkee

    New Member
    Svorsk - Scandinavia
    Sorry to dig up an old thread but I can shed some additional insight into what is meant by weak current..

    In Sweden they use "weak current" to classify electronic systems that are, in relative terms, essentially harmless. Basically anything with a few AA batteries qualifies; remote control, cell phone, laptop, car...
    A laptop on AA batteries? and a car?!
    Ok, so the boundaries are not clear and it gets confusing as well as slightly esoteric.
    Home appliances running of mains, such as toaster, old radio, tv, vacuum cleaner, would not qualify as weak current systems. An electric car would definitely also not qualify.
    So what about the laptop, and the car battery?
    Yes, well, they are not entirely harmless but a single AA battery hooked up to your heart isnt either.

    Now, in the context semiconductors of the original link (that is no longer available) I expect that you kind of got it right. Drain is mentioned, albeit in weird context (fingers?), and is one of three connectors (pins) on a Field Effect Transistor. So to understand what that particular article was most likely about I recommend googling "FET breakdown voltage".
    In essence; there is an electrical field (voltage) associated with a lack or abundance of electrons. This field will repel (abundance) or attract (lack) other electrons. In the FET one pin will exhibit this field and there is a semiconducting layer close to that pin in which the electrons will either be attracted towards the pin or repelled away. This will cause localized concentration of electrons in the semiconducting layer that in effect makes that area conductive. Connecting the other two pins through this particular area and the FET can function as a switch (or dimmer), controlled by the electrical field of the first pin.

    So, to end with the conclusion.
    A low or weak current is not defined per se, except maybe in countries like Sweden, so it tends to be relative to the other currents in the system.
    Looking inside a semiconductor the scale of it kind of makes Ohms law (U=IR) slightly off and electrical fenomena such as the Kirk? :) effect can affect the operation of the component, in this case seemingly offsetting the breakdown voltage level.

    But other than that, yes U=IR and P=UI

    Any one up for electronics studies? ;)
     
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    PaulQ

    Senior Member
    UK
    English - England
    In the domain of electronics (semiconductors), what is meant by "strong current" and "weak current"? I'm no scientist, but even I can tell from the following sentence that it's not "high voltage" and "low voltage":

    "The result of this is that breakdown can occur at a lower voltage in the case of a strong current than in the case of a weak current."
    The confusion seems to have arisen from not comprehending that semi-conductors are susceptible to heat and will fail if a lot of power is put through them. This power is expressed in watts. Watts are units of power. All energy (here, read 'power') is ultimately reducible to heat with respect to time.

    Although "low voltage" is generally classed as 12 or fewer volts, the quote simply says "lower voltage" - as a comparative this does not help the reader - there's probably some earlier reference that will make this clear.

    Now we need to read
    Current is the flow of electrons, measured in Amps. Presumably if there is a slow low flow-rate of electrons then you have a weak current.
    with that correction, we can see

    A voltage of 12 volts with a current of 2 amps will produce 24 watts - 24 units of power (i.e. heat)
    but
    A voltage of 240 volts with a current of 2 amps will produce 480 watts - 480 units of power (i.e. heat)
    and
    A voltage of 12 volts with a current of 10 amps will produce 120 watts - 120 units of power (i.e. heat)

    From this, we have
    "The result of this is that breakdown can occur at a lower voltage in the case of a strong current than in the case of a weak current."
    =
    "The result of this is that breakdown can occur at a lower voltage if the current is relatively high because volts x amps = watts = power = heat."
     

    Andygc

    Senior Member
    British English
    Post #6 explained the meaning of strong and weak current in the context of the OP. I'm afraid, nikkee, that the terms strong and weak current as you say they are used in Swedish do not work in English - certainly not in BE. We do talk of "low current" devices.
     
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