As the title suggests; I am trying to calculate the diameter of a wire given its length and resistance.

Specifications Length: 30.4CM (0.3 M) Resistance (30.4 Centimeter): 17 ohms

 

This may help, at least if it is the correct wire type.

 

You would need to know the resistivity of the wire. A resistance as high as 17 Ohms for a length of only ~30cm implies that this is a wire type used in heating elements.

 

View attachment 310566
This may help, at least if it is the correct wire type.

The table is incomplete my wire gauge is between 42 to 46 and the table ends at 40.

 

"i can not use measuring tool because wire is thinner then 0.1mm"
If you close-wind say 50 turns on a former and measure the length of the resulting coil you can get a good estimate of the diameter.

 

You can't use resistance to work out wire diameter, unless you know exactly what the wire is, in which case you would not have to measure it .
Why do you want to measure diameter ?
Is it a home work question?,

 

Yup

 

A metric micrometer has a resolution of one thousandth of a mm. Why not use one of them to measure the wire ?

Les.

 

As the title suggests; I am trying to calculate the diameter of a wire given its length and resistance.

Specifications Length: 30.4CM (0.3 M) Resistance (30.4 Centimeter): 17 ohms

First and foremost, you need to know what the wire is made of -- and what the resistivity of that material is.

30.4 cm is almost exactly 1 ft = 30.48 cm. so let's call it a foot.

IF it is "normal" copper wire, then the resistivity is generally considered to be 17.24 nΩ·m at 20°C, but this value varies a few percent depending on the material and processes used by a given wire manufacturer.

A good approximation is that #10 AWG has a resistance of 1 mΩ/ft and that this goes up by a factor of ten for every increase of ten in the wire size. So #40 AWG will have about 1 Ω/ft and #50 will have 10 Ω/ft. Thus, IF your wire is copper, it is smaller than #50.

You can use this factor-ten-for-change-in-size-of-ten with the table provided to see that the wire size would likely be #52, where you would expect a resistance of about 16.4 Ω.

But you say that your wire is between #42 and #46. How sure are you of this? If that is the case, then your wire isn't copper since the resistance copper wires in that range would fall between 1.6 Ω and 4.2 Ω.

FWIW: My understanding is that the AWG wire sizes only go up to #40, so anything smaller than that is not "official", however, the chart is very clearly defined and structured so that it can easily be extended to arbitrarily high (or low) wire sizes.

 

Hello,

Here is a page that shows upto AWG 60:
https://www.rembar.com/resources-technical-information-on-refractory-metals/american-wire-gauge-awg/
Here is a page that shows formulas on the wires:
https://www.rapidtables.com/calc/wire/wire-gauge-chart.html

A wire size of about AWG 52 of copper wire will give you the 17 Ohm per feet.

Bertus

 

Hello,

Here is a page that shows upto AWG 60:
https://www.rembar.com/resources-technical-information-on-refractory-metals/american-wire-gauge-awg/
Here is a page that shows formulas on the wires:
https://www.rapidtables.com/calc/wire/wire-gauge-chart.html

A wire size of about AWG 52 of copper wire will give you the 17 Ohm per feet.

Bertus

Thanks for your help, it was very helpful.

 

First and foremost, you need to know what the wire is made of -- and what the resistivity of that material is.

30.4 cm is almost exactly 1 ft = 30.48 cm. so let's call it a foot.

IF it is "normal" copper wire, then the resistivity is generally considered to be 17.24 nΩ·m at 20°C, but this value varies a few percent depending on the material and processes used by a given wire manufacturer.

A good approximation is that #10 AWG has a resistance of 1 mΩ/ft and that this goes up by a factor of ten for every increase of ten in the wire size. So #40 AWG will have about 1 Ω/ft and #50 will have 10 Ω/ft. Thus, IF your wire is copper, it is smaller than #50.

You can use this factor-ten-for-change-in-size-of-ten with the table provided to see that the wire size would likely be #52, where you would expect a resistance of about 16.4 Ω.

But you say that your wire is between #42 and #46. How sure are you of this? If that is the case, then your wire isn't copper since the resistance copper wires in that range would fall between 1.6 Ω and 4.2 Ω.

FWIW: My understanding is that the AWG wire sizes only go up to #40, so anything smaller than that is not "official", however, the chart is very clearly defined and structured so that it can easily be extended to arbitrarily high (or low) wire sizes.

I have a wire of 36 AWG and I compare it with that so I think that the AWG of the wire is 44 to 46. And the wire is metallic silver in color I think it's made of NICKEL OR electrical steel not sure between both. My calculation is giving a value that is near to nickel.

Thank you for your reply.

 

You would need to know the resistivity of the wire. A resistance as high as 17 Ohms for a length of only ~30cm implies that this is a wire type used in heating elements.

Yes it's used as a heating element

 

I think it's made of NICKEL OR electrical steel

Nichrome wire is commonly used for heating elements.

 

Nichrome wire is commonly used for heating elements.

Yeah but Nichrome is non-magnetic, And the wire used in sensor is magnetic

 

Wind the wire on a spool and use a scanner to image the spool ... if you know or set the resolution of your scanner 300dpi, 1200dpi, 2400dpi ... etc ... You can use almost any Graphical editing tool (Paint, Gimp, etc.) to give you the number of pixels. Then it's just a matter of using cross multiplication to determine the width (diameter) of the wire.

 

That was one kind of measurement I learned when became a 7 year old. The teacher said - now You have a stangel and must measure the 0.03 mm wide wire with three digits accuracy. After some painful brain inquisition minutes I said - I have no idea how, You have to show it. So, take the ball pen. Screw it to parts and take the inner ink-stick out. Depending on wire diameter wind on it accurate turn to turn gapless 10 or 25 or 100 turns with wire under test. Take stangel and squeeze coil longitudinally with moderate force. Read stangel. Divide the result to correspondingly 10 or 25 or 100. Write down the result.