# Metals rated for conductivity of electricity and heat **URL:** \ **Category:** Factual Questions\ **Created:** [March 21, 2014, 6:33pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238 "2014-03-21T18:33:41Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [March 23, 2014, 7:59pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/21 "2014-03-23T19:59:42Z")
> [@beowulff](#): > > I believe that the valves actually used Sodium as a coolant. [Sodium](https://www.youtube.com/watch?v=khJal_j7jpY) continues to be used in [Poppet valves](http://en.wikipedia.org/wiki/Poppet_valve). [Mercury](http://books.google.com/books?id=BtYbqYNbg0QC&lpg=PA824&ots=wM6gH4i1rn&dq=mercury%20cooled%20exhaust%20valves&pg=PA824#v=onepage&q=mercury%20cooled%20exhaust%20valves&f=false) has been used previously. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 23, 2014, 10:25pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/22 "2014-03-23T22:25:19Z")
> [@am77494](#): > > One of the severe applications is in a Steel Converter - that is the purification of molten steel after it comes out of the blast furnace. This was traditionally called the bessemer’s converter and revolutionized the steel era. In this process, **there’s a huge pot of molten steel** - [. . .] What material is that pot made of? And how is it (that material and the pot) manufactured? And what were the answers to these questions in Bessemer’s day? ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [March 23, 2014, 10:47pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/23 "2014-03-23T22:47:27Z")
> [@Senegoid](#): > > What material is that pot made of? And how is it (that material and the pot) manufactured? And what were the answers to these questions in Bessemer’s day? The pot is a steel frame lined with refractory brick and mortor. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [March 23, 2014, 10:51pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/24 "2014-03-23T22:51:30Z")
> [@Senegoid](#): > > What material is that pot made of? The pot is made of carbon steel - lined with refractory/ bricks. The pot can be tilted to pour out the molten metal. > [@Senegoid](#): > > And how is it (that material and the pot) manufactured? Its a simple vessel. It is lined with the refractory much like a house is built with brick and mortar. (castable refractory is almost the same consistency as mortar > [@Senegoid](#): > > And what were the answers to these questions in Bessemer’s day? The answers to your questions were pretty much the same in Bessemer’s day too. One of the oldest books on refractory was written in 1556 [cite](http://www.nssmc.com/en/tech/report/nsc/pdf/n9803.pdf). But mankind has known about refractory since the iron age. The science was not there to known refractory structure in detail (or compositions, or what made a good refractory when the slag was acidic…) but they knew enough. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [March 23, 2014, 10:52pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/25 "2014-03-23T22:52:36Z")
Si Amigo beat me to it. ---
**Author:** ![dougie\_monty](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@dougie\_monty](https://boards.straightdope.com/u/dougie_monty)\ **Post date:** [March 24, 2014, 5:52am UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/26 "2014-03-24T05:52:16Z")
> [@am77494](#): > > I resisted posting for a while, but here’s what I have observed/learned. > > Pure metals are rarely used in any engineering or real world building blocks. […] What I’d like to know is how well mercury conducts electricity in common mercury switches–according to the Wikipedia data it has about the same conductivity as iron. Asimov wrote that an aluminum wire three times as thick as a copper wire of the same length would conduct electricity just as well–and be considerably cheaper (for long distance transmission of electricity). Does mercury’s liquid state give it an advantage over iron, insofar as conductivity of electricity is concerned? ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [March 24, 2014, 1:57pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/27 "2014-03-24T13:57:49Z")
Mercury is only like iron is you consider 1x10[sup]-7[/sup] Ohm . m (Fe) to be like 9.8x10[sup]-7[/sup] Ohm . m (Hg). In other words iron is a better conductor than mercury. Resistance, aside from being futile, is typically built out as follows R = p\*l/A R = Resistance p = resistivity l = length A = cross sectional area If you want to compare materials of equal length (say in house wiring) then R[sub]1[/sub]/R[sub]2[/sub] = p[sub]1[/sub]\*A[sub]2[/sub]/p[sub]2[/sub]\*A[sub]1[/sub] For Al vs. Cu with resistances being equal I get the cross sectional area of the aluminium needing to be ~1.6 that of the copper wire. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [March 24, 2014, 2:11pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/28 "2014-03-24T14:11:44Z")
> [@dougie\_monty](#): > > What I’d like to know is how well mercury conducts electricity in common mercury switches–according to the Wikipedia data it has about the same conductivity as iron. … Mercury is used in switches and relays not for its great conductivity but because it is a liquid conductor and gives the following benefits : 1\> Low current situations : “_… the mercury reduces the contact resistance and associated voltage drop, for low-current signals where surface contamination may make for a poor contact_” [from Mercury Wetted Relay](http://en.wikipedia.org/wiki/Mercury-wetted_relay#Mercury-wetted_relay) 2\> Contact Erosion : This is the erosion of the contacts because of the plasma (spark) that is created when you turn the switch on or off. “_They are used where contact erosion would be a problem for conventional relay contacts. Owing to environmental considerations about significant amount of mercury used and modern alternatives, they are now comparatively uncommon._” [from Mercury Relay](http://en.wikipedia.org/wiki/Mercury-wetted_relay#Mercury-wetted_relay) 3\> Contact Bounce : This [wikipedia article](http://en.wikipedia.org/wiki/Contact_bounce#Contact_bounce)explains it very well. ---
**Author:** ![Bert\_Nobbins](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@Bert\_Nobbins](https://boards.straightdope.com/u/Bert_Nobbins)\ **Post date:** [March 24, 2014, 4:48pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/29 "2014-03-24T16:48:10Z")
> [@beowulff](#): > > Carbon (and now Tungsten) are used for filaments because of their very high melting points. The resistance is not a particularly important parameter. Oh yes it is. If tungsten had high conductivity we’d be running our incandescent lamps off 1 Volt, 100 Amp supplies. Which would be inconvenient, to put it mildly. Just think what house wiring would be like, and the light switches… ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 24, 2014, 5:35pm UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/30 "2014-03-24T17:35:17Z")
> [@Bert\_Nobbins](#): > > Oh yes it is. If tungsten had high conductivity we’d be running our incandescent lamps off 1 Volt, 100 Amp supplies. Which would be inconvenient, to put it mildly. Just think what house wiring would be like, and the light switches… That’s just an engineering/manufacturing problem. The filaments would need to get thinner, longer, and coiled more tightly, but it wouldn’t prevent lamp operation on standard house voltage/current. Tungsten’s resistance is only about 3x that of copper, so it can’t get _that_ much more conductive… ---
**Author:** ![Burns65](https://avatars.discourse-cdn.com/v4/letter/b/96bed5/32.png) [@Burns65](https://boards.straightdope.com/u/Burns65)\ **Post date:** [March 25, 2014, 4:57am UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/31 "2014-03-25T04:57:29Z")
> [@beowulff](#): > > I surprised you made this mistake. > The UV radiation is not caused by thermal energy, but rather electron impacts of the Mercury atoms, resulting in electron orbital transitions. of a flourescent bulb, not present in incandesent. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 25, 2014, 5:00am UTC](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238/32 "2014-03-25T05:00:27Z")
> [@Burns65](#): > > of a flourescent bulb, not present in incandesent. Yeah, that’s what **chronos** was talking about. Pay attention! [Previous page](https://boards.straightdope.com/t/metals-rated-for-conductivity-of-electricity-and-heat/684238.md?page=1)