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Magnetic field dependent on current only....

Discussion in 'Misc Electronics' started by qude, Jun 19, 2005.

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  1. qude

    qude Guest

    right?

    This means the 12volts/18ampere setup produce larger
    magnetic field magnitude (from the current flow) than
    the 110volts/2Ampere setup (noting that both produce the
    same 220 Watts power), right??

    Or does the larger 110 volts in the latter give more push
    to the 2 ampere resulting in similar magnetic field
    magnitude for both setups??

    If the answer is that the 12volts/18 ampere indeed
    produce larger magnetic field, do designers find it
    necessary to use larger voltage instead of larger
    current to prevent magnetic field interference?

    If the answer is that both produce the same magnetic
    field magnitude, then it means in larger voltage
    such as 110 volts, it pushes the 2 ampere more so
    it moves faster compared to the 18Ampere with 12
    volts that don't push it faster. If not, how can
    the magnetic field magnitude in both be the same
    (assuming they are the same).

    Thanks.

    qude
     
  2. redbelly

    redbelly Guest

    The 18 amp wire will have a larger magnetic field, at least in the
    vicinity of the wire. It is further complicated because the wires are
    usually coiled or double-coiled, and the geometry of the lead wires
    could have an effect as well.

    HOWEVER: magnetic fields are of no consideration whatsoever in light
    bulb design. Designers use the voltage source that is available: if
    the bulb is to be used in a household in the USA, this is 110-120 V.
    If for a household in most other countries, it is 220 V (or somewhere
    thereabouts). If it's for a car, then 12 V.
     
  3. sue jahn

    sue jahn Guest

    Correct!
    << In conclusion, ***all*** magnetic fields encountered in
    nature are generated by circulating currents. There is no fundamental
    difference between the fields generated by permanent magnets
    and those generated by currents flowing around conventional
    electric circuits. In the former case the currents which generate
    the fields circulate on the atomic scale whereas, in the latter case
    the currents circulate on a macroscopic scale
    (i.e., the scale of the circuit). >>
    http://farside.ph.utexas.edu/teaching/302l/lectures/node62.html

    No. Fewer charges need to move past a point in
    a second to transfer the same energy because they are
    moving faster. Tho' charges have energy, (angular momentum)
    it is not created nor destroyed. The energy that does
    the work is the mass(equivalent energy) of the charge in motion.
    Hmmm... Frequently higher voltages are used to avoid
    thick wire. I can't think of an example. There are other
    techniques that are more effective, but in principle you
    are correct.
    But it isn't. You got it right above.

    Sue...


    that both produce the same magnetic
     
  4. Don Kelly

    Don Kelly Guest

    --
    Don Kelly

    remove the urine to answer
    ---------
    Who were you answering? There is no indication of what you are saying
    "right" to. Please include at least some of the material you are responding
    to.

    The magnetic flux density due to a wire carrying current I is proportional
    to the current and inversely proportional to distance. The presence of other
    current carrying wires (such as the necessary return path(s) affect the flux
    density so consideration of a single wire in space is not a realistic
    option(effectively you have a single turn coil with a return conductor
    infinitely far away).
    The field due to a current of 2A is 1/9 that due to a current of 18A at a
    point external to the wire.

    Is this of importance to decisions as to what voltage is to be used? Not
    really.

    There is an optimum voltage level depending on the power to be transferred
    and the distance it is to be transferred (at a given frequency). Rule of
    thumb- more power and or longer distance- go to higher voltage. This is not
    a physical rule- but an economic one. That is why AC transmission put
    Edison's DC systems out of business. You can transmit 100MW at 200V for a
    distance of 200 miles but the cost would be horrendous compared to doing it
    at 140,000V. However, to use 140,000 V to supply a home would be rather
    dangerous, expensive, and ridiculous so 120/240 is a good practical and
    economic balance. (Sue, you should know this- examples are all around :))
     
  5. redbelly

    redbelly Guest

    He was saying "right?" to the header of this thread, "Magnetic field
    dependent on current only...."
     
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