1

Technology / Re: Does cold weather damage the batteries used in an EV?

« on: 13/01/2025 16:20:33 »

Q: If electric cars are not good in extreme cold, then why do people keep buying Teslas in Canada?
A: As the owner of two gasoline-powered pick-ups and the driver of a diesel at work, questions like this always make me laugh.

So given the choice, he sticks with ICE!

The problem of diesel turning to glue should have been solved years ago: JETA1 is essentially similar to diesel and works down to -40 C all day every day. Preheating diesel isn't beyond the wit of man, and as 40% of the energy of fossil fuel appears as heat once the engine is running, you can do a lot to reflow the exhaust over the catalytic converter if you need to.

The power required to heat the cabin is exactly the same regardless of the source, but as I pointed out in reply #1, it is "free" with an ICE but reduces the range of a BEV.

AFAIK Antarctic scientists use properly specified ICE vehicles with no real problems, and most Scandinavians seem to get around OK on ICE snowmobiles. There's much to be said in favor of aircooled engines at low temperatures, though aircooled diesels haven't found much favor in the light aviation business.

2

Technology / Re: Does cold weather damage the batteries used in an EV?

« on: 12/01/2025 15:10:56 »

The perceived difference in risk is due to the fact that ICEs don't spontaneously combust. The usual point of unintentional ignition occurs when a poorly-maintained vehicle has been running fast and hot, the fuel line comes adrift or the carburettor (remember those?) floods, and a backfire on overrun blows flames out of the air intake.

However well-maintained a BEV may be, early lithium batteries gradually developed in an internal short circuit and self-immolated entirely at random. The problem was occasionally reported in phones and computers but really hit the headlines when Boeing Dreamliners  became a fire hazard. I  think the problem has been  largely eliminated, but the fact remains that a burning BEV is very difficult to extinguish and almost impossible to salvage, which is one reason that insurance premiums have doubled in the last few years.

3

Technology / Re: Does cold weather damage the batteries used in an EV?

« on: 11/01/2025 18:01:35 »

1 KWh of energy used in the motor will move the car  X amount of miles. 

Estimate 3 - 5 miles per kWh. It's not quite linear with battery capacity for a given car as the bigger battery weighs more!

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Technology / Re: Does cold weather damage the batteries used in an EV?

« on: 11/01/2025 10:17:17 »

Battery efficiency generally decreases at low temperatures, the effects being summarised as an increase in internal impedance. Thus more energy is lost to internal heating when work is done. Oddly, when starting an internal combustion engine at low temperatures it sometimes helps to crank the starter motor a few times and wait: the warmer battery can now deliver enough current to spin the motor fast enough to start the engine.

Some early BEVs had a battery preheat cycle but I think battery performance now tolerates at least UK winter conditions without it.

You can estimate the cold weather range loss from the cabin heater specification. You generally need about 5 kW to keep  the windows clear in a small car at 0 deg C, and maybe 20 kW on a really cold day.  The advantage of an internal combustion vehicle is that  hot air is an inevitable waste product, so thanks to increased air density, it actually goes further on a cold day!

5

Just Chat! / Re: Free lectures

« on: 04/01/2025 21:37:59 »

That's wrong isn't it, or at least morally wrong?

Not at all. You pay to see a movie, and if you leave the cinema you have to pay to see it again. As a student, you pay to be taught and examined to a timetable, and it's up to you to remember what you were taught or keep notes.

The mission statement for most universities never included free continuing access to lectures, though many offer library services to alumni. The Open University happily recycles its broadcasts but always made its money (academics have to eat) from tuition and examination fees and the sale of course textbooks.

When you buy a car or a house, you don't expect the seller to update it free of charge every couple of years.

6

New Theories / Re: what is temperature?

« on: 28/12/2024 14:09:01 »

Thermistors work from around -50C to 300C. I have used them to measure temperature changes of 1mK to +/- 1μK. If you want a traceable calibration in the room temperature range, no real problem - use an oil bath and a platinum resistor to fix absolute points to better than 0.05K

7

New Theories / Re: How does Hamdani explain the twins paradox?

« on: 28/12/2024 11:04:52 »

There isn't a problem, just a common misconception that Δt = 0 for all systems, simply because it is a near-enough approximation for many purposes.

If you are brought up to believe that π = 3, you will be amazed by the "tape measure paradox". You might even become a philosopher!

8

New Theories / Re: Origin of magnetic force

« on: 22/12/2024 09:25:47 »

What do I have to do to patent my invention?

Your national patent office should have a simple online form for filing a provisional patent. If not, use the UKPO. The important thing is to establish priority of invention in the broadest possible terms, and a provisional filed in any country does that. Then decide whether you are going to make any money from it. Talk to a prospective manufacturer under an NDA (use an online form or get a solicitor to draft one for you). If it looks profitable, get a patent attorney to draft and submit it, if it is your first patent - not cheap, but you will learn a lot from the PA.

Your national patent office website is the best source of information, not a chatbot.

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New Theories / Re: How does Hamdani explain the twins paradox?

« on: 21/12/2024 23:32:47 »

the developers will have to correct the answers.

Not possible. The whole point of a chatbot is that it scours cyberspace for anything that looks like information, without human intervention. The quantity of crap increases exponentially as (a) crap begets more crap and (b) crap is not subject to experimental verification and retraction and (c) some crap is compiled by other bots and posted as "research", so the consensus becomes incoherent or  just plain wrong.

10

Just Chat! / Re: What does it cost? What does it do?

« on: 16/12/2024 22:18:06 »

Not sure about the forum cost but the sponsors obviously think it is money well spent.

The NS broadcasts are justifiable for exactly the opposite reason to a forum! Suppose it costs one penny per listener to broadcast an interview with a Nobel laureate to an audience of 100,000 schoolkids. If you gave them each a penny, would they be able to engage 100,000 lecturers of  similar status for even one minute?

Massive difference between "Reithian" broadcasting, which distributes the best to everyone, and "social" media which distributes the worst to idiot "followers". Forums associated with good radio allow in-depth discussion and personalised explanation of stuff that may have been abbreviated in the live show. 

Whilst we get a fair sprinkling of barking idots here, we do also get sensible answers to genuinely interesting questions, and jousting with Hamdani  and indeed your goodself does make one think critically about stuff we take for granted.

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General Science / Re: What would the kinetic energy of a bullet falling from 2Km be?

« on: 11/12/2024 17:04:35 »

The terminal speed of a 9 mm bullet is around 250 ft/sec. This is considerably less than the muzzle velocity of an AK47 (1000 - 1500 ft/sec) but dangerous if not always lethal.

12

The Environment / Re: How are global warming and world population expansion linked?

« on: 11/12/2024 09:38:56 »

The disgrace of Syria is nothing to do with housing shortage but decades of corrupt government and religion. Governments don't build houses (except in communist countries) but, for the most part, merely facilitate speculative building.

Every country needs fewer people.

But those countries where the population exceeds any possibility of a comfortable and sustainable life tend to be those with the least per capita carbon footprint. So if you are a Believer, you can't blame overpopulation for climate  change.

Believer or not, it is nevertheless apparent that where it results in famine, climate change defines overpopulation.

Climate change is inevitable and to some extent predictable, so the sensible thing to do is to adjust the human population to a sustainable  density everywhere.

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Just Chat! / Re: Help!

« on: 10/12/2024 19:33:59 »

If you are replying to the last post in a topic, have you tried using "quick reply" at the bottom of the topic page?  No requirement for a title.

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Chemistry / Re: Shrink ray or growth ray, how could they work?

« on: 07/12/2024 16:16:50 »

    What we have a real opportunity to do, is to change the di-electric or practical ε in the environment around the atoms.

We might substitute other atoms or dopants but this won't merely alter the bulk size of our target, but its chemistry and physics - in other words you will be making a completely different object.

Consider a protein molecule surrounded by water. If you substitute liquid hydrogen sulfide for the water you might indeed cause the protein molecule to shrink, but the mouse that works by the interaction of proteins with water will cease to do so. Or to take a simpler example, changing the dopant of a semiconductor will alter the effective density of the electron cloud of the parent material, but p- and n-doped substrates have very different functions.   

15

Question of the Week / Re: QotW - 24.12.12 - Is there any way to harness nuclear energy other than steam?

« on: 06/12/2024 20:12:35 »

There are already some promising semiconductor thermocouples with > 20% efficiency, apparently.

16

Just Chat! / Re: Should smartphones be banned from the dinner table?

« on: 02/12/2024 12:34:35 »

Further thought. I have attended a few committee dinners in pub restaurants. Time was that these were places for quiet conversation in an acoustically "soft" environment, separated from any live gigs in the "spit and sawdust" bar.

Nowadays the acoustic environment is  "hard" (no sticky carpets, big glass windows....) and filled throughout with umpteen decibels of piped noise, over which you have to shout to be heard by your nearest neighbor.

So it is quite likely that those under the age of 40 have never experienced conversation over a meal, and don't know how to behave at a family dinner.

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Just Chat! / Re: Theories to start a new world.

« on: 01/12/2024 09:49:31 »

Desert Island Discs is still running on Radio 4. The limit is 8 discs (now tracks), one book, and one luxury.

Presumably we are leaving on a rocket, so I'd take Newtonian mechanics, the atomic theory of chemistry, and probably the Krebs cycle if I'm not allowed the whole biochemistry library. Then my descendants would understand how we got here, and religion (the reason why we left Earth) might not take root.

DID participants are asked to name the one track they would save above all else. Gerry Mulligan's "Golden Notebooks"

encompasses the apex of civilisation in four minutes and should set the tone for humanity's next gig.

18

General Science / Re: Can an electron travel a bit in a copper wire for inertia?

« on: 26/11/2024 15:15:29 »

Save your typing fingers! "Free electricity" is not possible. The work done separating the ends of the wire will exceed any energy available to make electrons leave it.

The answer to a sustainable future for homo sapiens is to reduce our standard of living or reduce our population. The latter is obviously more desirable, saves a lot of effort, and costs nothing.

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New Theories / Re: what is temperature?

« on: 25/11/2024 08:55:20 »

Perhaps I should have said "of particles within a confined space" but I guess that's still not absolutely explicit.

The atoms within your rod have no idea how fast the rod is travelling in space if the speed is constant, but they do know what happens when they bash into each other. If you decelerate the rod by crashing into a brick wall, the energy transferred to the wall will be the  0.5mv² component of the rod plus its heat content, but we are no longer talking about the original bounded ensemble.

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Physics, Astronomy & Cosmology / Re: What Causes This Optical Effect?

« on: 22/11/2024 12:44:58 »

Not disputing one word of what you have said but I fear you have got the "wrong end of the stick". The OP was talking about an illuminated room versus a dark exterior and your example was a detailed analysis of an illuminated room with daylight outside.

Mea culpa, but geometric optics is commutative!