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How conductors/resistors affect electric fields?

  1. Jan 14, 2016 #1
    Disclaimer: I'm not sure if this is the correct forum.

    An ideal conductor (ideal = no resistance) is essentially taking the electric field at one terminal and connecting it to the other terminal. Charge moves when it is in an electric field, electric field strength is in Volts per meter, or Newtons per Coulomb. But a zero resistance conductor would appear to an electric field like no distance at all between two terminals at different potentials...(?) So the charge would flow unimpeded from one terminal to another in an electric field of field strength which we would think about as being Newtons per Coulomb. Our ideal conductor has a constant electric field strength throughout, and how long our ideal conductor is wouldn't matter, but would it not matter because (i) the ratio of potential difference to distance multiplied by the distance just gives the potential difference between the terminals regardless of the field strength at any point in an ideal conductor of any given length, and so therefore the Newtons per Coulomb measure of the field that is lower in a longer conductor is also multiplied by a greater distance to give the same Joule per Coulomb difference in potential between the terminals. Or (ii) we can forget about the Volts per Meter in an ideal conductor and just think of it as recreating the potential of the higher terminal at every point throughout its length until it reaches the lower terminal...(?)

    So, as the charge flows from one terminal to another, is it continuously converting its higher terminal potential energy into "kinetic" energy until it reaches the lower terminal at 0 volts (0 is a reference only I understand)? That seems more intuitively right.

    I am aware that, though they are all measured in Ohms, there are some conceptual differences between resistance, reactance and impedance. I am also aware that in an insulating material, the opposing dipoles setup in the molecular structure of the insulator in the presence of an electric field are strong enough to basically counteract the electric field before the field can penetrate the insulator.

    Are the opposing dipoles in a resistor (or other resistive material) lowering the net field strength, so that the lower terminal (or some point near the lower terminal) sees a weaker field strength than it otherwise would?

    Is this why putting say 3 light bulbs in series that are 30, 40 and 50 W @ 120V (and correspondingly 480, 360 and 288 ohm), will cause the actual power output of the bulbs to be nearer to 5, 4 and 3 W @ 120V each? Ie, the resistance of the elements impedes the communication of field strength between the terminals, meaning the charge itself is experiencing a lower field strength, even as it leaves the higher terminal, applying less force to the charge....but that wouldn't explain why the current is lower...so is the current lower due to another effect, say the electrons bumping messily around inside the resistor, causing a momentary back current, that smooths out quickly, applying some back pressure at the higher terminal, causing less current to leave whilst still maintaining the same voltage at the higher terminal...? Only certain materials are superconductive near at extremely low temperatures, is this because despite eliminating the resistive effects of the electrons chaotic motions there is still an opposing dipole in most materials, or would opposing dipoles be eliminated in any conductive material near absolute zero but the effect of electrons bumping around still create resistance (and superconductors somehow do away with this)?
  2. jcsd
  3. Jan 14, 2016 #2


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