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Length of 250g of 37 SWG (40 AWG) wire?

Discussion in 'Electronic Components' started by Alex Coleman, Feb 10, 2007.

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  1. Alex Coleman

    Alex Coleman Guest

    What is the approximate length of 250g of 37 SWG (40 AWG or 0.17mm
    diameter) enamelled copper wire?

    Where can I see a chart showing this sort of info for other gauges of
    enamelled copper wire?
  2. Fred Bloggs

    Fred Bloggs Guest

    It's just possible a manufacturer may have date, like these people:
  3. Fred Bloggs

    Fred Bloggs Guest

  4. Fred Bloggs

    Fred Bloggs Guest

    You did say "enamelled" so I ass-ume you mean magnet wire:
  5. Density of copper = 8.94 gm/cm3 (various sources give 8.92 to 8.96.)

    I don't know what the weight of the enamelling is, but as copper is more
    dense than iron, I'll ignore it.

    250g of copper / 8.94 gm = 27.964 cm3.

    Cross section area = PI * r (in cm here) squared = 0.00022698 cm2.

    Length is 27.964/0.00022698, so 123200 cm.

    You might have to take the weight of the enamel into account with that thin
    wire, but I think a calculation might get close enough.
  6. My wire tables say AWG 40 is 33,410 ft/lb.

    So, for 250g =0.551155655 lb would be 18,414 ft = 5,600m, about 4.6x
    as long.

    The reason for the discrepancy-- the diameter of AWG 40 is given as
    3.145 mils or about 0.08mm. Square the ratio and we have the
    difference accounted for.

    Best regards,
    Spehro Pefhany
  7. Or, to put it another way, how long is a piece of metal string? >:)

    What with the differing vlues for density, the unknown thickness and weight
    of enamelling, and what may or may not be a confusion somewhere between
    radius and diameter, the room for error is large. The OP gives 0.17 mm as a
    diameter, but yours might be a radius, given a figure of 0.08. I've no idea
    which is right, but that half/double between the two values is suggestive.
  8. MassiveProng

    MassiveProng Guest

    Apples and oranges?

  9. MassiveProng

    MassiveProng Guest

    Copper wire... ALL copper wire is given as the gauge of the WIRE
    part of the "wire". Not enamel or anything else.

    Otherwise all current capacity declarations/calculations would be
    off from maker to maker, when in fact they are merely adjusted for
    factors related to insulation material and thickness and thermal
  10. MassiveProng

    MassiveProng Guest


    Basic math belongs in the basic math group.
  11. So it is. I went looking. I don't know where the OP's value of 0.17 comes
    from, I just took it at face value.
  12. jasen

    jasen Guest

    yup, but when they weigh a spool of enamelled wire the deduct the weight of
    the spool and the label but not the weight of the enamel.

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