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

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

1. ### Alex ColemanGuest

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 BloggsGuest

It's just possible a manufacturer may have date, like these people:
http://mdmetric.com/tech/wirewt.htm

3. ### Fred BloggsGuest

or http://www.interfacebus.com/Copper_Wire_AWG_SIze.html

4. ### Fred BloggsGuest

You did say "enamelled" so I ass-ume you mean magnet wire:
http://www.mwswire.com/tech_book.htm

5. ### LostgallifreyanGuest

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. ### Spehro PefhanyGuest

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. ### LostgallifreyanGuest

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. ### MassiveProngGuest

Apples and oranges?

Bwuahahahahah!

9. ### MassiveProngGuest

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
properties.

10. ### MassiveProngGuest

Bwuahahahahaha!

Basic math belongs in the basic math group.

11. ### LostgallifreyanGuest

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. ### jasenGuest

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.

Bye.
Jasen