1

Technology / Re: Can you explain this demonstration of a capacitor?

« on: 22/03/2023 14:35:48 »

I don't know where the ammeter is connected.

Yes you do, follow the wiring:


MIT vid.png (13.57 kB . 1048x591 - viewed 789 times)

So there is at least one path from plate to plate through the ammeter.

No there isn't, the power supply has been disconnected, so the only connnection to the live plate is the insulated support on the stand, and the electroscope.

Is there any discernible pattern or explanation for the deflections shown on the ammeter during this part of the demonstration?

Yes, as above, the knob is on the live side of the meter.

2

Chemistry / Re: Why adding a fizzy drink to ice does the temp drop below the temp of the ice?

« on: 26/02/2023 18:24:47 »

I heard that

Have you checked to see whether it does?

I can see why the evaporation of CO2 will reduce the temperature, with or without the ice.

3

General Science / Re: Why Does Making A Sandwich Enable Ewe To Cut Anything?

« on: 02/02/2023 12:19:55 »

If I have a stack of sandwiches to cut, I do them one at a time, cutting them all in one just squashes them. I cut by rolling the curvature of the blade, drawing the blade across them just tears.

4

Technology / Re: Electricity Generation via treadmill. Can one person generate enough?

« on: 20/01/2023 11:37:14 »

The issue isn't whether you can produce a useful amount of power (useful for doing what? cycle lights run off a dynamo), it's whether you can do it at a useful efficiency. The human body is about 20% efficient, far worse than a combined cycle power station (55-60%), and growing the food to power it accounts for a quarter of global CO2 emissions.

5

Chemistry / Re: Strange aroma off smokeless fuel or has covid ruined my snout?

« on: 05/01/2023 16:08:21 »

A small unrelated Query...

Is Covid never ever gonna go away?

Will WE have to keep dealing with it, live & die with it like ForEver?

This doesn't bode well:


Covid.jpg (115.87 kB . 900x648 - viewed 697 times)

6

General Science / Re: Advent calendar maths question!

« on: 15/12/2022 00:37:42 »

0,1,2,3,4,5

0,1,2,6/9,7,8

7

Technology / Re: How to learn process control system in practice?

« on: 17/11/2022 17:33:53 »

bends in the road can take the car in front out of the beam for a few seconds. So it appears to "remember" the speed of the car in front for perhaps 5 seconds

But the car in front could do an emergency stop in the 5 seconds it's out of view, can the assisted braking respond in the time left after the car reappears?

The more complexity in the control system, the more responsibility on the driver to understand it in detail, and to understand (and take action) when it hits corner cases where it doesn't do what you intend.

The more complexity in the control system, the more opaque it generally gets.

if the car in front is slowing to turn a corner, and I can see that it will be safely out of the way before I get close; the radar system (configured for sensitive mode) sees the car in front slowing to a near stop in the line of sight, and rapidly slows down my car. Flicking off the speed control for a second resolves this problem.

The problem with automation is fighting it to stop it doing what you don't want can often make more work than doing the job yourself.

8

Technology / Re: Does wi-fi harm the environment?

« on: 08/11/2022 14:15:26 »

Radio engineers have been working with radio for a century, and so have groups of professional users, if it were harmful they would have showed some signs of increased morbidity & mortality by now, but I'm not aware of any evidence of that. Concerns about safety didn't start to gain any currency until mobile phones put radio into the hands of lay people.

9

Cells, Microbes & Viruses / Re: Why are arm pit stains so difficult to remove?

« on: 25/10/2022 18:18:42 »

i suspect the deodorant to be the Cause

Me too.

I don't use deodorant, and my clothes don't stain.

10

Technology / Re: Can I get an electric gas boiler?

« on: 15/10/2022 13:24:22 »

Do you have any links ?

12 million of them in less than 10 seconds:
https://www.bing.com/search?q=domestic+chp&qs=n&form=QBRE&sp=-1&pq=domestic+chp&sc=10-12&sk=&cvid=8865F76F517743F9A56CF487A783354A&ghsh=0&ghacc=0&ghpl=

11

Physiology & Medicine / Re: Link between supercentenarians and smoking?

« on: 31/05/2022 10:51:24 »

"a good deal of" is not an objective way of measuring things. Relevant questions are how many smokers vs non-smokers reach the age of 100, and what proportion of centenarians are smokers compared with nonagenarians, octogenarians and septuagenarians.

12

Plant Sciences, Zoology & Evolution / Re: Have animal reactions to mirrors and windows been studied?

« on: 28/05/2022 00:50:28 »

https://twitter.com/buitengebieden/status/1523065975654195201
https://twitter.com/buitengebieden/status/1527524346872332289
https://twitter.com/philipnolan1/status/1515260865892732928
https://twitter.com/Yoda4ever/status/1519881660744962049

13

Marine Science / Re: Why is the ocean salty?

« on: 26/05/2022 14:10:16 »

There are salts in the soil which get flushed into the rivers and then the sea by rainfall. When the sun evaporates the water to form more clouds and rain the salt gets left behind in the sea, so if you repeat that cycle for billions of years the salt in the sea becomes more and more concentrated.

14

Physiology & Medicine / Re: is psychiatric labelling complete nonsense?

« on: 18/04/2022 17:15:20 »

This makes an interesting read. In essence, Smail argues that most mental health problems are a normal reaction to abnormal circumstances, and therapy fails because it seeks to gaslight the patients into believing that they having an abnormal reaction to normal circumstances. The only therapist I've met who could communicate rationally without being deliberately obtuse left the job saying "I'm fed up of the way the patients are patronised, and fed up of pretending we're helping when we know we aren't".

My advice to anyone contemplating getting themselves a mental health record would be think very carefully about whether you want your healthcare blighted by Diagnostic Overshadowing for the rest of your life.

Connections by Johan Hari is a thoughtful and intelligent look at how our modern way of life creates many of the health problems that are reaching epidemic levels.

15

Physics, Astronomy & Cosmology / Re: Which weighs more, a litre of ice or a litre of water?

« on: 15/04/2022 16:15:39 »

"Houston, we have a problem. We have a leak. Our oxygen is rapidly venting"

"Hello, this is NASA Houston here. We are currently experiencing unprecedented call volume, and all our operators are busy. Please be assured that your call is important to us. If you're calling to order a pizza, please press #, otherwise hold the line and your query will be dealt with as soon as possible. You are currently number 46 in the queue."

16

Physics, Astronomy & Cosmology / Re: How do you calaculate the capacitance of two unsually shaped plates?

« on: 21/03/2022 17:46:38 »

The quick way is to calculate the capacitance of the wide end, then either triple it if the spacing is 2mm as in the diagram, or quadruple it if the spacing is 3mm as in the text.

17

The Environment / Re: Why is the air inside a car worse than outside?

« on: 07/11/2021 00:03:30 »

Numerous experiments have shown that cyclists riding in rush hour traffic are breathing cleaner air that the occupants of cars. The explanation offered is usually that the air intakes on the cars are closer to exhaust level than the cyclists face.
https://www.sciencedirect.com/science/article/abs/pii/S0048969701007586
https://can.org.nz/system/files/Research-0402-Emissions.pdf

18

Technology / Re: What are some low-tech ways to address climate change?

« on: 06/11/2021 18:56:30 »

like population control, limiting meat-based agriculture/diet, not clear-cutting our forests, different approach to transportation, less materialism etc.

The problem with any of these actions is that it makes you less fit. A country that limits births and keeps its forests will be taken over by the countries that burn the candle at both ends and consume the resources declined by the country doing the better thing. So my contribution is a world government with real authority, that has yet-to-be-identified goals in mind and not necessarily the immediate comfort of voters. Thus it will probably not consist of elected leaders. Such a thing would form if there were a common enemy such as aliens, but we apparently don't consider climate change to be such a common enemy.

I've been arguing this for years, the only way out of a Prisoners' Dilemma is an authority that has the power to enforce Cooperation rather than Defection. This is why I'm convinced that there will be no meaningful action taken on climate change until it's already too late, people won't accept any policies that compromise their own lifestyle until it's their own lifestyle being compromised by the climate.

Recently I have been wondering if it might produce a bit more action to have conferences where the speaker is obliged to say what they've already done rather than what they're promising to do, along with a big display on the wall indicating how far ahead or behind their quota they are.

19

Geology, Palaeontology & Archaeology / Re: Is this possible?

« on: 21/10/2021 18:39:23 »

https://en.wikipedia.org/wiki/Chicxulub_crater

20

General Science / Re: How did a dead Duracell AA battery come back to life in my clock?

« on: 14/10/2021 13:01:18 »

Deja vu

https://www.thenakedscientists.com/forum/index.php?topic=81103.msg620803#msg620803