Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Some questions on terminology (for native English speakers)

  1. May 2, 2016 #1
    Hello! I am a beginner in English terminology.
    I know that direct current is a flow of electricity that moves in one direction only (i.e. does not change its direction).
    I also know that alternating current is an electric current that reverses direction at regular intervals.

    However, I cannot find in my dictionaries the proper English terms for:
    1) a DC current, which does not change its intensity at all,
    2) a current, which does change its intensity, but not necessarily its direction (that is, the general term for AC, pulsating DC, DC smoothly petering out etc.)

    I find several word combinations, which may or may not be the right terms:
    1) steady current, constant current, time-independent current, stationary current;
    2) time-dependent current, time-varying current, variable current.

    Which are the standard (conventional) terms, OK but awkward terms and wrong (misleading) terms?
    Is there any authoritative source in English (a textbook, an encyclopedia, a standard etc.) which I can quote when discussing these terms with my compatriots?

    If you don't know the standard names, what do YOU call these currents?
     
    Last edited: May 2, 2016
  2. jcsd
  3. May 2, 2016 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    However, I cannot find in my dictionaries the proper English terms for:
    1) a DC current, which does not change its intensity at all,[/quote]
    this is called a steady or constant current. It is given a capitol I for it's symbol.

    this is called a varying current. It is given a lower case i of i(t) to show it changes with time.

    These are all acceptable - any English speaker who knows electronics will understand what you mean.

    Any English language text book will do.
     
  4. May 2, 2016 #3
    However, I cannot find in my dictionaries the proper English terms for:
    1) a DC current, which does not change its intensity at all,
    2) a current, which does change its intensity, but not necessarily its direction (that is, the general term for AC, pulsating DC, DC smoothly petering out etc.)

    I find several word combinations, which may or may not be the right terms:
    1) steady current, constant current, time-independent current, stationary current;
    2) time-dependent current, time-varying current, variable current.

    I would suggest,
    (1) A steady current
    (2) A varying current
     
  5. May 2, 2016 #4

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2016 Award

    We English speakers are not consistent, you'll find the terms often used loosely.

    I like Simon's post.

    Think of it as a hierarchy
    Direct means as you said unidirectional. But that does not preclude variations.
    This would be Direct Current as it's unidirectional
    diode18.gif

    (okay it's voltage, but current through the resistor has same shape)

    This is approaching "steady"

    diode23.gif
    I'd call it DC with Ripple and put a number on the peak to peak ripple as % of average

    and at some point where the ripple ibecomes insignificant to the task at hand it'd be okay to call it "steady"
    and that point is up to the author, or the person explaining it.
    In most but not all applications 0.1% ripple is negligible .

    If the graph is an absolutely straight line as from a battery it's steady, unquestionably, and also direct.
    If it's well enough filtered and regulated it might as well be called steady even though with a big enough microscope you can see variations

    poorly filtered or unfiltered as first picture it's direct but not steady.



    Any help ?

    old jim
     
    Last edited: May 3, 2016
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Some questions on terminology (for native English speakers)
  1. PA speaker question (Replies: 2)

  2. Speaker Questions (Replies: 0)

Loading...