Donated Eskalab Spectrophotometer by CuriousMarc
. Source. Single-mode and multi-mode optical fiber by 
Ciro Santilli 35 Updated 2025-04-18 +Created 2024-06-26
Ciro Santilli 35 Updated 2025-04-18 +Created 2024-06-26From a practical point of view single-mode:
As such, typical applications are:
- single-mode optical fiber: longer distance communications across buildings and cities
- multi-mode optical fiber: shorter distance communications e.g. within a single data center
Then there are some more hardcore threads actually pondering about specific cost trade-offs:
From a mathematical point of view:
- multi-mode: en.wikipedia.org/w/index.php?title=Optical_fiber&oldid=1229833804#Multi-mode_fiber:
Fiber with large core diameter (greater than 10 micrometers) may be analyzed by geometrical optics. Such fiber is called multi-mode fiber. In a step-index multi-mode fiber, rays of light are guided along the fiber core by total internal reflection.
- single-mode: en.wikipedia.org/w/index.php?title=Optical_fiber&oldid=1229833804#Single-mode_fiber:
Fiber with a core diameter less than about ten times the wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic waveguide structure, according to Maxwell's equations as reduced to the electromagnetic wave equation. As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along the fiber. Fiber supporting only one mode is called single-mode.
Another difference is that single-mode fiber usually uses lasers as the light soruce, while multi-mode fiber usually uses LED:
Is it realistic?
Yeah, bitch! Magnets! scene from Breaking Bad
. Source. The interest of the magnetic hysteresis graph is that it serves as an important characterization of a :This curve will also tell you how many turns of the coil will be needed to reach the required field.
- its area gives you the hysteresis loss of the transformer, which is a major cause of efficiency loss of the component
- some key points of the curve give important characterizations of the core/material:
- Saturation magnetisation
- magnetization strength without field
- how much field you need to demagnetize it
Theoretical magnetic hysteresis plot
. Source. 1989. 1989 and they were making such awesome materials. It is hard to understand why university still exists given this.
Shows how you can obtain the magnetic hysteresis curve with an AC source plus an oscilloscope in XY mode. youtu.be/pXukVix5Pcw?t=193 clearly shows the measurement circuit.
2020, thanks COVID-19. Like other UNSW Physics YouTube channel videos, the experimental setup could be made clearer with diagrams.
But this video does have one merit: it shows that the hysteresis plot can be obtained directly with the oscilloscope XY mode by using an AC source. The Y axis is just a measure of the total magnetic field induced by the primary coil + the magnetization of the material itself.
The first application of mobile phones was in motor vehicles by Ciro Santilli 35 Updated 2025-04-18 +Created 2024-06-26
Ciro Santilli 35 Updated 2025-04-18 +Created 2024-06-26Early models were heavy and not practical for people to carry them, so the main niche they initially filled was being carried in motor vehicles, notably trucks where drivers are commercially driving all day long.
It also helps in the case of trucks that you only need to cover a one-dimensional region of the main roads.
Easy-to-Build Electromagnet lifts over 50 lbs by Dorian McIntire
. Source. Fun, but zero reproducibility.Solenoids are simpler to build as they don't require insulated wire as in modern electrical cable because as the electromagnetic coils don't touch one another.
As such it is perhaps the reason why some early electromagnetism experiments were carried out with solenoids, which André-Marie Ampère named in 1823.
But the downside of this is that the magnetic field they can generate is less strong.
Pinned article: ourbigbook/introduction-to-the-ourbigbook-project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 2. You can publish local OurBigBook lightweight markup files to either OurBigBook.com or as a static website.
Figure 3. Visual Studio Code extension installation.
Figure 5. . You can also edit articles on the Web editor without installing anything locally. Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension. 
- Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact