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B Can a wire be called a resistor?

  1. Apr 12, 2017 #1
    Can a wire be called a resistor? Also do all circuits require a resistor? If no then give an example of a circuit which doesn't have a resistor. Please thanks
     
  2. jcsd
  3. Apr 12, 2017 #2
    :welcome:
    Are you asking if wires have internal resistance?
    For the second question, I suppose you could have a circuit without a resistor, but I don't see what the point of it would be.
     
  4. Apr 12, 2017 #3

    ZapperZ

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    Your questions are vague.

    A "wire" where? A wire in real life, unless it is a superconductor, is a resistor because it has a non-zero value of resistance. However, it has a considerably less resistance than most of the other components of the circuit, so one often ignores that in ordinary cases, but not in all.

    A "wire" in a typical circuit diagram are not considered to be a resistor and are idealized to be a perfect connector from one part of the circuit to another.

    Draw a battery connected to a capacitor. Is there a resistor in your circuit diagram? How about in real life? Is there a resistance in the wire and in the battery itself?

    You need to clarify exactly the scenario and the context of your questions. Otherwise, they are vague.

    Zz.
     
  5. Apr 12, 2017 #4
    In most cases, wires have resistance. Some resistors are basically wires. Sometimes the resistance provided wires is important to the function of the circuit - in which case you would expect them to be in the circuit diagram.
    Here is a low pass filter - with no resistor: 250px-Lowpass_Pi_Filter.svg.png
     
  6. Apr 12, 2017 #5

    sophiecentaur

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    Talk to an Electrical Power Engineer. Despite the fact that their 'wires' tend to be very thick, they are also very long and their resistance accounts for a significant proportion of your Electricity Bill.
    On Schematic Circuit Diagrams, we draw lines, joining components and (usually) we treat them as having no resistance because it allows us to do calculations to sufficient accuracy. If wire resistance happens to be comparable with the resistance of those components then we have to take account of the resistance of the wires.
    There is actually no practical circuit that you can think of that contains no resistance because components (even superconducting components) are all connected by a practical conducting path. There is another relevant issue. When there is any change of current flowing in a circuit (at switch-on or with AC) some electromagnetic power will be radiated into space. Every circuit acts like a radio antenna, to some extent and that is, in effect, an additional resistor in the circuit.
     
  7. Apr 12, 2017 #6

    CWatters

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    As above.. yes wires have resistance. Sometimes it is negligible and can be ignored, sometimes not.

    Many circuits don't have resistors in them. Examples...

    House or car lighting circuits
    Electric fans or food mixers
    Car starter circuit.

    Some circuits may have resistors in them but could probably be built without them eg a calculator.
     
  8. Apr 13, 2017 #7

    davenn

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    that's incorrect thinking and as Zz and CWatters have said there are plenty of examples if specific resistor-less circuits

    why would you want to introduce additional unnecessary losses in the circuit ?


    Dave
     
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