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
    208
    7
    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
    23,179
    6,978
    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
    208
    7
    Wow! Ok, then with just one resistor, is it a IV converter, or VI converter? Both....?
     
  4. hexreader

    Active Member

    Apr 16, 2011
    332
    137
    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
    2,596
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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
    4,130
    1,096
    Both.
     
  7. WBahn

    Moderator

    Mar 31, 2012
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    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.
     
  8. AllanGH

    Member

    Oct 1, 2013
    19
    3
    Consulting Schrödinger's favorite oracle, the answer is that it is simultaneously neither, and both...until you take measurements:

    If you measure the current through the resistor, then it is a series circuit.
    If you measure the voltage across the resistor, then it is a parallel circuit.

    Seriously...give it a try.
     
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  9. MrChips

    Moderator

    Oct 2, 2009
    17,342
    5,342
    Does it matter whether you label it as series or parallel?
    The outcome is the same in any proper circuit analysis regardless of what you call it.
     
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