I plan on using a 1 ft long, 0.005" diameter platinum wire as part of an electrode. The wire will be bare but will be inside a hollow plastic tube that has an inner diameter of 0.08". It needs to be able to carry a maximum of 1 mA for a length of 10 minutes, while not exceeding 60(adsbygoogle = window.adsbygoogle || []).push({}); ^{o}C. I'm not sure whether this wire meets this requirement, so I searched online and found the Preece equation (W.H. Preece, Royal Soc. Proc., London, 36, p464, 1884).

[tex]I_{fuse} = ad^{\frac{3}{2}}[/tex]

where [itex]a[/itex] is the fusing constant, and is equal to 5172 according to the Standard Handbook for Electrical Engineers, 6th ed., Sec 15, p153, and [itex]d[/itex] is the diameter of the wire in inches.

Plugging these values into Preece's equation yields:

[tex]I_{fuse} = (5172)(0.005)^{\frac{3}{2}}[/tex]

[tex]I_{fuse} = 1.83 Amps [/tex]

So according to Preece's equation, the platinum wire can carry a maximum of 1.83 Amps before reaching its melting point of 1,768^{o}C. I'm not sure how accurate this answer is since it doesn't take into consideration the length of wire, elapsed time, or the increasing resistivity of the wire with increasing temperature.

Is there another way I can find out whether the wire can meet the requirement?

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# Finding current and temperature of platinum wire

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