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Really basic resistance question, but not sure.

  1. Jan 7, 2008 #1
    Hey guys,

    I feel like an idiot asking this, but if the question is talking about 1k7 ohms of resistance, am i to believe that is the same as 1700 ohms?

    Thanks ^^

    James
     
  2. jcsd
  3. Jan 7, 2008 #2

    stewartcs

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    Yes.

    CS
     
  4. Jan 7, 2008 #3

    Shooting Star

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    What is this notation?
     
  5. Jan 7, 2008 #4

    stewartcs

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    I think its crap. Doesn't really make sense to me, but I've seen it on spec sheets before (then they put = 1700 ohms beside it in parenthesis).

    CS
     
  6. Jan 7, 2008 #5

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    From what you say, I presume it's done by engineers?
     
  7. Jan 7, 2008 #6

    berkeman

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    Dunno if it's crap, but you do see it in various places, so it's good to be familiar with it.

    1k7 = 1.7k Ohms

    1r7 = 1.7 Ohms
     
  8. Jan 7, 2008 #7

    Shooting Star

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    Just one more question. You both say this is seen in various places, like spec sheets. Where else?
     
  9. Jan 7, 2008 #8

    stewartcs

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    That's a new one I haven't seen.

    I suppose it may be to standardize the use of a comma (in Europe and other places) and a decimal in the US.

    i.e. 1,7KOhms compared to 1.7KOhms.
     
  10. Jan 7, 2008 #9

    berkeman

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    It's common on European schematics. Either in application notes, or in customer schematics (in my work, I help out with customer design reviews fairly often, so I see a lot of schematics from all over the world).

    Also, you'll sometimes see medium-size power resistors labeled with the 2R2 type of notation, if the value is written on the resistor (as opposed to using colored bands).
     
  11. Jan 7, 2008 #10

    ranger

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    Isn't it also possible for that notation to represent a potentiometer? I could swear that I've built circuits using 4k7 pots.
     
  12. Jan 7, 2008 #11

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    And that would mean...?
     
  13. Jan 7, 2008 #12
    I've seen the notation on the resistors themselves before.
     
  14. Jan 7, 2008 #13

    f95toli

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    Which simply means a potentiometer with a maximum resistance of 4k7, i.e. 4700 Ohms

    This notation is very common and often very conventient; especially when you have small letters on a component since you do not have to use a point since e.g. 1.7k can easily be misstaken for 17k. 1k7 and 17k look very different.
     
  15. Jan 7, 2008 #14

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    > 1k7 = 1.7k Ohms

    > 1r7 = 1.7 Ohms


    The k I've understood, but what is the 'r'? What would be 720 in this notation? (I don't know what they use for 100. But, suppose they use h, then it'll be 7h2, right)
     
  16. Jan 7, 2008 #15

    berkeman

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    I belive the R is just to show it is a resistor.
     
  17. Jan 7, 2008 #16

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    And the 'k'?
     
  18. Jan 7, 2008 #17

    berkeman

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    Kilo = 1000

    Since there is no prefix for unity, they apparently picked the "R" for the resistor decimal point designator.

    You will also see 47R for 47 Ohms, BTW.
     
  19. Jan 7, 2008 #18
    The electronics use k with the meaning Kohm, not k as 1000x. It's just a coincidence. They never use h or d to mean x100 or x10.
    Resistors of several kilo ohm to a hundred kohm are very common, so they just say 2.2 k or 2k2, 100k etc.
    They also use r as ohm, just because in electronic circuit schematics, resistors are often noted as R1, R2 etc...
     
  20. Jan 7, 2008 #19

    berkeman

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    Why do you think it's a coincidence that the prefix k is used for kOhm? How many Ohms in a kOhm?
     
  21. Jan 7, 2008 #20
    If not, they should use k, h, d as well. But i have never heard. I use to spend some time working with electronics circuits , electronics devices and the like, and we used the word k so often that we never thought it's x1000 (in fact it is), I just thought kohm is a unit which is used as often as ohm (even more).
     
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