Wikipedia:Reference desk/Archives/Science/2024 August 30

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August 30

Dead batteries come back to life?

A friend of mine has a battery-powered clock. It stopped running. It was over a week before he got replacement batteries. When he went back to the clock, it was running again. Is there an explanation for this? Bubba73 ^{You talkin' to me?} 16:04, 30 August 2024 (UTC)

This writeup has one theory:[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:08, 30 August 2024 (UTC)

This effect is readily seen with a flashlight when the cells (battery) are approaching the end of their useful lives. After a short period of operation the light from the flashlight becomes dim. If the operator turns the light off and waits a few seconds, then turns it back on, the light is usefully bright again but only for a few seconds before it becomes dim again.

The active materials in the cell migrate to get to their electrode and that takes time. Similarly the exhausted product migrates away from its electrode. Allowing the cells to rest for a short while allows these materials to migrate to/from the electrodes and improve the density of the active materials surrounding each electrode. Dolphin (t) 22:13, 30 August 2024 (UTC)

Temperature also plays a role. Batteries near their end of life are more likely to fail if the room turns cold. If it warms up again the clock may restart. Shantavira|^{feed me} 09:04, 31 August 2024 (UTC)

An additional factor may be a slight irregularity in a clock's mechanism, such as a slightly mis-shaped or corroded cog tooth, that is overriden by the power of a good battery, but provides enough resistance to the weaker power of a near-dead one to stop the clock. If the clock is then moved or disturbed by vibrations, this may jar the tensioned mechanism past the obtruction, restarting the clock for a time. {The poster formerly known as 87.81.230.195} 94.1.209.45 (talk) 09:18, 31 August 2024 (UTC)

it might be that the relationship voltage-current is non-linear and/or hysteretic. when the clock doesn't get enough juice, it stops drawing any current, the battery "recovers" via the chemical mechanism above, the clock starts drawing current again. the system "clock -- battery" thus oscillates which manifests itself in just such intermittent operation Aecho6Ee (talk) 18:07, 3 September 2024 (UTC)

some devices do this (poweroff when voltage drops below a threshold and back on when it rises) intentionally as part of "brownout detection" or "undervoltage lockout" Aecho6Ee (talk) 18:14, 3 September 2024 (UTC)

Metric units in the UK

In the United Kingdom, is room space and building height measured in metric units? And has rail transport seen any metrication in its history? --40bus (talk) 20:38, 30 August 2024 (UTC)

Rightmove are the UK's biggest online property agents. As you'll see from their website, they quote room space in sq ft but with conversions to sq m. I don't know about rail transport. Mike Turnbull (talk) 20:49, 30 August 2024 (UTC)

40bus: "On 5 May 1975, rail traffic switched to metric measurements for loads, capacities, tare weights and brake force. On the traffic side of the railway we are chiefly concerned with distance and weight. As to distance, no metrication is planned for the time being... (i.e. distance is still measured in miles, as are road distances). [2] Alansplodge (talk) 16:22, 31 August 2024 (UTC)

And are there any everyday things that are measured in metric units in the United States, as oppsoed to scientific things? --40bus (talk) 21:11, 30 August 2024 (UTC)

Some commodities are. You can get liter bottles of soft drinks, for example. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:23, 30 August 2024 (UTC)

2 quart soda bottles haven't been used in decades and decades. Did they keep the same price for awhile to say at least you're getting more? Sagittarian Milky Way (talk) 04:22, 1 September 2024 (UTC)

Highway distances: metric signs in Tennessee. (Not a representative sample!)  Card Zero  (talk) 21:39, 30 August 2024 (UTC)

Other states also post both miles and kilometers. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:13, 30 August 2024 (UTC)

Indeed, that site has more.  Card Zero  (talk) 22:36, 30 August 2024 (UTC)

Engine capacities in cc, esp. motorcycles. Doug butler (talk) 21:55, 30 August 2024 (UTC)

I thought Harley-Davidson measured their V twins in cubic inches. --TrogWoolley (talk) 10:38, 1 September 2024 (UTC)

Ammunition is measured in mm. So are camera lenses. And mechanical pencil lead widths. And a lot of other things that are too small to be comfortably measured in inches -- such as jewelry components. Wrench sets are made for both metric and US customary units. Backpacks and other luggage are sized in liters. We run 5K and 10K races.

A lot of components of food and supplements (carbohydrates, cholesterol, sodium, caffeine, etc.) are measured in grams or mg, especially on standardized nutrition labels -- and they've crept into the vernacular from there. Nobody talks about how many ounces per day of protein or grains of caffeine one should consume. -- Avocado (talk) 02:03, 31 August 2024 (UTC)

Guns and ammo are in inches. .357 Magnum, for example. Though much less common than they once were, Mile run events are still held in America. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:25, 31 August 2024 (UTC)

The Dream Mile race is held in Oslo (Norway metricated in 1875). Alansplodge (talk) 16:16, 31 August 2024 (UTC)

Miles are still used in Norway, but those are metric miles of 10 kilometres. The traditional Norwegian mile was 11298 metres. English miles have obviously never been in common use in Norway, but the abovementioned race is an English mile long. PiusImpavidus (talk) 17:48, 31 August 2024 (UTC)

Oh, yeah, not saying we don't use customary units for those things at all. Just that we do commonly use metric ones for them, too (such as 9mm for ammo). -- Avocado (talk) 13:53, 31 August 2024 (UTC)

Ammo calibres are more like names than actual measurements. .223 Remington and 5.56mm Nato are the same size, despite 5.56mm not being the exact conversion of 0.223", and neither being the actual measurement of the bullet. Iapetus (talk) 10:47, 2 September 2024 (UTC)

Most things related to electricity, such as a 120-volt receptacle or a 9-volt battery. Jc3s5h (talk) 14:03, 31 August 2024 (UTC)

Small lengths of time in the US are commonly specified in the corresponding SI base unit, the second. --Amble (talk) 22:47, 30 August 2024 (UTC)

I hope that the US will metricate at least some everyday things in next 20 years so that US-related articles will use metric units first in 2044. --40bus (talk) 17:25, 31 August 2024 (UTC)

I hope we don't we're the last bastion of old units, just big and isolated enough to prevent zero Earth unit diversity Sagittarian Milky Way (talk) 04:34, 1 September 2024 (UTC)

I second that emotion. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:56, 1 September 2024 (UTC)

I don't know everything about British railways, but if I'm to believe openrailwaymap, it appears that some British lines have a speed limit in kilometres per hour and some have a limit in miles per hour that is an obvious conversion from a round number in kilometres per hour. Look at the high speed lines like High Speed 1 (not the older, improved lines with 125 mph limit), DLR and some of the more recent lines of the London Underground. So it looks like a conversion has started. PiusImpavidus (talk) 16:39, 31 August 2024 (UTC)

The Grenfell Tower fire led to the United Kingdom cladding crisis. Most of the building height measurements are only or primarily given in metres. -- Verbarson  ^talk_edits 20:49, 31 August 2024 (UTC)

But article Tower Bridge, for example, uses imperial units first. And it is a building. --40bus (talk) 21:44, 31 August 2024 (UTC)

Tower Bridge is 130 years old. The sources (and the sources' sources) are therefore far more likely to use Imperial units. The response to the Grenfell fire is contemporary, so better reflects current practices. -- Verbarson  ^talk_edits 05:06, 1 September 2024 (UTC)

Our Miles per hour article says: Miles per hour is also used on British rail systems, excluding trams, some light metro systems, the Channel Tunnel and High Speed 1 (the Channel Tunnel and its High Speed link obviously extend into France and beyond). Alansplodge (talk) 11:30, 1 September 2024 (UTC)

It's a surprisingly modern bridge really. The Time Machine was written the next year.  Card Zero  (talk) 13:06, 1 September 2024 (UTC)

Real steampunk, in fact. (Edit) My mistake - it was hydraulic. -- Verbarson  ^talk_edits 13:35, 1 September 2024 (UTC)

Not mistaken at all, Verbarson! The operations were performed by hydraulic pressure, supplied by hydraulic accumulators, but "[w]ater at a pressure of 750 psi (5.2 MPa) was pumped into the accumulators by a pair of stationary steam engines" – see Tower Bridge#Hydraulic system. {The poster formerly known as 87.81.230.195} 94.1.209.45 (talk) 21:45, 1 September 2024 (UTC)

Ah, thank you. When I saw it was 'hydraulic', I somehow assumed it used the London high-pressure network (which was itself steam-powered). What makes it feel most like steampunk is the combination of ancient (Gothic turrets), more recent (suspension spans for the approaches) and up-to-date (steam-hydraulic powered bascules) styles and technologies. -- Verbarson  ^talk_edits 22:17, 1 September 2024 (UTC)