resistance

Discussion in 'General Electronics Chat' started by sharanbr123, Oct 26, 2014.

  1. sharanbr123

    Thread Starter Member

    Sep 29, 2014
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    0
    Hello All,

    The resistance of a resistor depends on what?
    Is it just the property of the material?
    Does it depend on length and width/diameter?

    A related question - referring to the attached figure, is it ever possible to charge the node to 5 V?
     
  2. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    2) No. It is connected to the most negative voltage of the circuit with a wire.

    1) Resistor technology went through different mixtures of carbon and clay before they became thin films on ceramic sub-stratas. You will probably read several pages of Wikipedia before you absorb all the history of resistor evolution.
     
  3. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    No that is resistivity.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,120
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    In practice, no. You can buy a complete range of resistors, from very low ohms to very high, that all share an identical package. You can only tell them apart by the color bands they are marked with.

    What varies somewhat reliably with size and shape is the heat dissipation rating.
     
  5. BR-549

    Well-Known Member

    Sep 22, 2013
    1,987
    388
    The resistance of a resistor depends on what?
    Atom structure. Temp. Background fields.

    Is it just the property of the material?
    No. An external field can change resistance. And it depends on how you define “property” of a material. Is temp a property or state or is it external?

    Does it depend on length and width/diameter?
    Yes, as does everything else.

    A related question - referring to the attached figure, is it ever possible to charge the node to 5 V?
    Yes. According to modern physics, at sometime in the past or sometime in the future, that node did or will reach 5 V.
     
  6. sharanbr123

    Thread Starter Member

    Sep 29, 2014
    49
    0
    Dear BR,

    Not sure if you are being sarcastic.
    ANyway, doesn't this defy Ohm's law?
    With little understanding I have, presence of a resistance makes sure that there is always a voltage drop.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    sharan,, nothing personal, but I have mentioned several times that you need to work on your terminology.

    Can you tell me what is wrong with that question?

    The answer to the question you meant to ask is, yes if you introduce a switch between the end of the resistor and the negative terminal of the battery and set it to open.
    The end of the resistor will then be at +5 volts potential.
     
    Last edited: Oct 26, 2014
  8. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
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    The "voltage drop" has two meanings.
    1 - the "voltage drop" as a drop in voltage leve, eg. power supply voltage drop by 0.1V when we connect a load resistance.
    2 - "voltage drop" as a voltage present across external component. So in your circuit we have a 5V battery and resistor connected across this battery. So we can say that the voltage drop across resistor is equal to 5V.
     
  9. BR-549

    Well-Known Member

    Sep 22, 2013
    1,987
    388
    Please forgive me. I was trying to give you the most up to date, modern scientific information. The study and critique of such things is my passion.

    I know it's hard to believe and understand.....but modern science changes the time and place of when and where ohm's law works. They do this to many laws and constants.

    Ironically the constants that they say change......don't. And the ones that they say don't change.....do.

    As for your understanding.....resistance does not cause a voltage drop. When you turn your circuit off.....the resistance is still there and there is no voltage drop. It takes current to induce a voltage across a resistance. Also resistance controls the rate of current, not voltage.
     
  10. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    Watch your terminology. Perhaps you meant to say rate of charge.
     
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