Is a Resistor from V+ to Gnd Considered Parallel or Series?

Discussion in 'Analog & Mixed-Signal Design' started by johnyradio, Oct 1, 2018.

  1. johnyradio

    Thread Starter Active Member

    Oct 26, 2012
    178
    5
    This image shows parallel and series with multiple resistors.

    [​IMG]

    But, if there's only ONE resistor, it will be the identical circuit! So, would we call that "parallel" or "series"?

    thx
     
  2. WBahn

    Moderator

    Mar 31, 2012
    22,987
    6,883
    Yes.

    If there are only two components (a resistor and a power source in this case) then it is both in series and in parallel.

    Two components are in series if and only if any current flowing in one must flow in the other. So they are in series.

    Two components are in parallel if and only if any voltage appearing across one must appear across the other. So they are in parallel.

    This is known as a degenerate case where the distinctions between the two vanish.
     
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  3. johnyradio

    Thread Starter Active Member

    Oct 26, 2012
    178
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    Wow! Ok, then with just one resistor, is it a IV converter, or VI converter? Both....?
     
  4. hexreader

    Active Member

    Apr 16, 2011
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    132
    Can be either, depending on whether you give it a constant V or a constant I

    Constant V is a far more common occurrence (such as from a battery) than constant I.

    Constant I is starting to become more common, for driving LEDs.

    Whilst thinking of a resistor as VI or IV converter might be valid, it is a very unusual way to think about a resistor.
     
    Last edited: Oct 1, 2018
  5. OBW0549

    Distinguished Member

    Mar 2, 2015
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    Neither. Since in that case there's no distinction between the two, just call it what it is: merely a resistor connected across a voltage source.
     
  6. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,010
    1,031
    Both.
     
  7. WBahn

    Moderator

    Mar 31, 2012
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    6,883
    Depending on the context, either way may be a reasonable view. Of course, that applies to all resistors regardless of connection topology since the relationship between V and I is a characteristic of the device, not the connections.
     
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