Wikipedia:Reference desk/Archives/Science/2023 October 9

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October 9

Any significant difference between these two locks?

Is one functionally safer than the other? [1] [2] 68.174.155.22 (talk) 12:28, 9 October 2023 (UTC)

both are deadlocks; they require a key to lock and unlock. The second type is susceptible to "spreading": if you kick hard enough or manage to get a crowbar between the door and the frame you can in principle spread the lock from the frame (with only the mechanical strength of the door resisting) by a distance greater than the length of the bolt at which point the door will open. the first type will actively resist this type of attack by adding the strength of the lock and bolt to the resistance to spreading. in most common installations this is a bit overkill since the screws holding the lock to the door would likely fail first. 2A01:E0A:D60:3500:35AF:6AAD:9C95:98A6 (talk) 18:09, 9 October 2023 (UTC)

Amazon has some reviews of the Segal deadlock and of a Schlage single cylinder deadbolt in the B60 series; the images of the latter appear different, though, from that on the wayfair website. Unfortunately, they do not offer much insight on the safety. You could send one of each to the LockPickingLawyer :).  --Lambiam 18:32, 9 October 2023 (UTC)

Slew rate: what is a Tesla/sec?

I was reading this overview from NASA regarding PEMF: https://technology.nasa.gov/patent/MSC-TOPS-96. It says waveforms used high rising and falling slew rates on the order of Tesla/sec. What is a Tesla/sec? I tried reading the Slew rate article, and it says the slew rate measurement is usually V/us. I also found Tesla_(unit) and that says One tesla is equal to one weber per square metre. I don't understand how this related to the slew rate measurement.

I don't have a strong science background. Can someone explain what Tesla/sec means in this context?

RudolfRed (talk) 18:56, 9 October 2023 (UTC)

In the article slew rate I would jump on the bit or any other electrical quantity in the first sentence. Tesla is the unit of magnetic flux density (something like the magnetic field strength), and the slew rate in the case of PEMF would be the rate of change of the magnetic field, so roughly one Tesla per second. --Wrongfilter (talk) 20:00, 9 October 2023 (UTC)

Bear in mind that in engineering 'order' often means within a factor of 10, so in this case roughy 0.3-3 T/s Greglocock (talk) 21:31, 9 October 2023 (UTC)

Courtesy link: pulsed electromagnetic field therapy. --Trovatore (talk) 21:48, 9 October 2023 (UTC)

Also, a Tesla is a BIG unit. For comparison, a refrigerator magnet is about 0.005 Tesla. One Tesla is roughly the field of an MRI machine. So a system that can slew at a rate of one Tesla per second is changing magnetic field incredibly fast. PianoDan (talk) 02:12, 10 October 2023 (UTC)

If a refrigerator magnet gives you 5 millitesla, then flipping it around 100 times per second gives you 1 T/s – but only in a very small volume. PiusImpavidus (talk) 08:00, 10 October 2023 (UTC)

The maximal absolute value attained by $\textstyle {\frac {\text{d}}{{\text{d}}t}}0.005{\text{T}}\sin(100\cdot 2\pi \,t/{\text{s}})$ is even $3.14{\text{T}}/{\text{s}}.$ Can we scale this up to reach $1{\text{TT}}/{\text{s}}$?  --Lambiam 12:11, 10 October 2023 (UTC)

Ramping up and down to a field of 5 mT 100 times a second is NOT the same from an engineering standpoint as ramping up to a field of 1 T once per second. I didn't read the initial article carefully enough.

On doing a bit more research [3] it appears the actual device is even LOWER maximum field (on the order of ~0.1 mT) and higher frequency. PianoDan (talk) 14:17, 10 October 2023 (UTC)

Thanks, everyone, for the replies and the information. RudolfRed (talk) 17:04, 10 October 2023 (UTC)