Electrical Resitance

Ever heard of Google ?

mperature?

Gee that's kind of a broad question. Do you have any particular metal in mind?

For pure metals at high temperatures the resistivity is roughly linear with temperature. (A high temperature being defined as being greater than the Debye temperature for that material.)

George H.

temperature?

Around +0.4% per degree C for lots of pure metals. Alloys can be other values, including some near zero.

--

John Larkin Highland Technology Inc

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

temperature?

It varies, by metal, purity, alloy, and temperature range (as well as other factors such as annealing and external stresses and magnetic field). Pure metals tend to increase more-or-less linearly with temperature, around room temperature. Most (not all) alloys have lower tempco than pure metals around room temperature. At very cold temperatures more dramatic things tend to happen. For example:

or vs. temperature with under strong magnetic fields:-

Or it might drop suddenly to exactly zero, depending. For example, I'm told that if you cool U238 to 2.4 K and squish it enough (1.2GPa) the resulting alpha phase will go superconducting.

Here is an interesting paper:-

of course he has smartass.

maybe everyone should just Google it and ignore newsgroups?

temperature?

and besides, both John and Spehro give better answers that anything you can Google. we're lucky they're active on this group.

temperature?

I'm assuming the test has ended and it's safe to pass this on:

See the video

Actually that's not a good answer for people in the business of purity testing of metals by means of resistivity, tempco, and thermoelectric properties. They're expecting absolutely wild deviations with just parts per gazillion impurity concentrations...

values,

of metals by means of resistivity, tempco, and thermoelectric properties. They're expecting absolutely wild deviations with just parts per gazillion impurity concentrations...

I thought it was an excellent answer.

values,

esting of metals by means of resistivity, tempco, and thermoelectric proper ties. They're expecting absolutely wild deviations with just parts per gazi llion impurity concentrations...

LOL- I'll concede a 'good'- but 'excellent' would be a stretch.

values,

testing of metals by means of resistivity, tempco, and thermoelectric properties. They're expecting absolutely wild deviations with just parts per gazillion impurity concentrations...

We make our own current shunts. We start with a sheet of manganin and have it punched or photo-etched to our design shape. Then we fold it, anneal it, bond it to a heat sink, and terminate. The magic is to get the transient response right, namely to keep the heatsink eddy current effects down and have a near-zero hum pickup area. Most heat-sunk shunts and resistors, like those Vishay things or the MIL metal-case resistors, have ghastly time-domain behavior from eddy currents and thermoelectrics. Open-air "railroad" shunts have huge hum profiles.

temperature?

A near-critical sphere of something would have, in effect, a huge specific heat.

temperature?

--- Without exception, the resistance of an elemental metal will increase as its temperature increases, giving it what is referred to as a "positive temperature coefficient of resistance."

-- JF

values,

of metals by means of resistivity, tempco, and thermoelectric properties. They're expecting absolutely wild deviations with just parts per gazillion impurity concentrations...

values,

esting of metals by means of resistivity, tempco, and thermoelectric proper ties. They're expecting absolutely wild deviations with just parts per gazi llion impurity concentrations...

Chuckle*, No one will every accuse you of being overly modest.

I like knowing it's goes as ~T, then the change with T goes as about 1/ T So I'd guess +0.33% at 300K. (Alloy's are just screwed up metals from a 'certain' physics point of view.)

George H.

values,

testing of metals by means of resistivity, tempco, and thermoelectric properties. They're expecting absolutely wild deviations with just parts per gazillion impurity concentrations...

I'm just being objective. My reply was factually correct and nicely hedged.

Pure platinum is +3920 PPM/K around room temp. Copper, silver, lead, aluminum are all about the same. Nickel, occasionally used for RTDs, is around 6000.

Snarl. Snap.

her values,

y testing of metals by means of resistivity, tempco, and thermoelectric pro perties. They're expecting absolutely wild deviations with just parts per g azillion impurity concentrations...

Cool, Do you use some folded design to keep the pick-up out?

I been thinking about these little diode temp sensors.

I worry about sticking different metals together, it's not clear to me when I get 'battery/chemical action' between two metals.

With the diodes I was thinking about wetting a bit of Al and sticking the collector of a transistor to that. There's then this Al/solder/transistor-lead sandwich.

George H.

ed text -

Maybe they should when it's a homework question.

her values,

y testing of metals by means of resistivity, tempco, and thermoelectric pro perties. They're expecting absolutely wild deviations with just parts per g azillion impurity concentrations...

This is a nice graph

From copper.org There's lots of other graphs... I don't get the magneto-resistance one.

George H.

ed text -