Physics

Only differed by frequency, wavelength but they are all fundamentally done by light, is that right? When you put a physical credit card or stored value card near a payment device provided by the merchant, is it using the identical technology as that when you put your mobile phone close to the device and pay with your mobile phone without physical card?

It's said latent heat of boiling water or steam will cause more damage. I find that when I cook and the water is boiling, if I put my hand near the steam I wouldn't get as much pain as I accidentally put my hand directly into the boiling water. I would probably hold on a few seconds under the steam but if I put my hand into the boiling water I won't be able to withstand one second. Why is that?

Couldn't an extremely large concentration of neutrinos, for reason's unkown, explain the observations that leads to dark matter? Perhaps there are regions in space that trap's neutrinos, like a black hole does with light?

Hello. What is the table I should look for to find which materials have the capability of holding/storing more amount of heat ? I do not care how fast they conduct the heat if their parameters are related; and what is it called ? specific heat ?, density ? specific gravity ? , heat conductivity... Example : 1 Kg or iron at 100C or 1 Kg of water at 100C or 1 Kg of concrete at 100C or 1 Kg of wood at 100C... And does it go by mass, or by volume ? As in 1 litre of iron, 1 litre of concrete, 1 litre of water instead ... ?

This is going to save people's lives you all please share it no advertising please in another forum I got questioned why I post link to a web page. I can't post all of it here. if the google page is not ok you can download documents from here: no advertising please

Good morning. Had 3 spare solar panels dormant for months; decided to put them to work for helping heating the house instead of sheltering spiders in the basement. Panel1---panel2---panel3-------------hotplate stove Panels are 40VDC / 400Watts each; the series yields 120VDC capable of 1200Watts at full insolation. Yes, the 'burner' gets very hot and has to be contributing warmth into the dwelling. Now; is it better to warm the air during daylight or put a pot and heat water (or rocks? or junk metal?) lasting more time into night time ? What would you do ?

Hello I struggle about this concept of time If I understand right, time is a measure unit we created to measure/understand movements right ? for example, this man is 50 yo, this man passed 50 earth/sun rotations... I mean we use time because it's easier than talking using movements only.... ? It took 7 seconds for me to drink this glass of water the glass been drunk while our planet gone from point A to point B Could we talk using movement without time ? Do time really exist or is it a measure unit we created to explain movements ?

hi, this may be a dumb question, but I'm wondering (read carefully every details) : Can we use a very strong electric field to separate electrons from nucleus of some hydrogen or helium gas (a macroscopic quantity, not just some particles, it's not a particle accelerator), then accelerate the nucleus' at high speeds using electric fields, then making them collide in large quantities... (and maybe uses the electrons at the other side to go back with nucleus at the end) and then use the fusion energy obtained to power the whole machine ? thanks

Hello all. When the switch is on, 10 Amperes flow trough it. When the switch is turned off, there is arcing between its contacts. ---------------------------------------------------------------------------------- Added resistor to circuit, consumes 0.025A tiny current. When the switch is on, 10 Amperes flow trough the switch. When the switch is turned off, is there arcing between its contacts ?

Hi. Solar radiation in all its flavors of infrared, visible light, ultraviolets and all the rest whatever they be hitting a roof for a standard figure of 1KW/m2 What device could collect the most solar energy of all kinds installed on a roof ? Photovoltaics can collect about 18% into direct current.

i decided i want to try to "understand" how a plane can fly. if thats even possible for a layman like me. so ive been watching a bunch of videos, but still so many questions. and you cant ask a video anything. so, i thought i would try here. because this is essentially a tricky subject, i thought i would break it up into mini subjects. so the first subject is Bernoulli's principle. now i know this is not the whole picture of why a plane can fly, but it is some of the picture. so, first up i thought it better to try to understand this. so, as i understand, Bernoulli's principle states that an increase in a fluids speed lowers its pressure. the thing i cant find on…

In recent days I have done a few experiments measuring the current of water as it goes up from 9 volts up to 36 volts, and following Ohms law to convert it to resistance. And I discovered a very interesting trend. In between 9 and 18 volts, there is a massive drop in resistance (by around a 40% reduction) but then as I go up to 27 volts, its a 5% reduction, and is even less of a reduction when reaching 36 volts. I've done this experiment a few times and this has continued to happen. This is it visualised on a graph; I am curious to know why this happens, why there seems to be a reduction as I go from 9 to 18 volts, yet the reduction…

I am living in a subtropical region and we are in summer now. Every time when I come out from a hot bath (I never bath with cool water) and before I dry my body, I feel quite cool, but room temperature at night is still over 85 F. Is it because of the high heat capacity of water droplets on my body which has absorbed heat around my skin?

I notice alcohol easily kills houseflies; when I can hit 'em. (Yes, I finish them off just to be sure.) But they're crafty little things, and usually manage to maneuver around it, especially when they can tell I'm coming. I want to be able to spray them from far enough away that they can't tell I'm coming, but that the alcohol still hits them with enough force to kill them, or at least leave them immobile enough to finish off. Is there any way to create a stronger spray bottle than the kinds alcohol is usually stored in? (Sidenote: Yes, if I ever in the future intend not to live alone, I will ensure I get a locked safe to keep the bottle in so it doesn't fall …

Looking for all known CONTROL OF and CONTROLLED applications of the big 4. So you may say, for electromagnetism, we can create and control it with batteries, generators, capacitors, semiconductors etc.

Regards. Lenz law shown here ---> https://www.youtube.com/watch?v=N7tIi71-AjA How to, where to, probe, measure, confirm a voltage presence of the eddy current as in the copper pipe shown above ?

Is there any study or research on approximately how much damaging or harmful UV could reach inside a room in an apartment building of a city without any UV film or curtain? It's said most harmful UV is already blocked / absorbed by the glass of windows or other obstacles before reaching inside. Is it validated?

I’m curious about the experience of a family member. They were with a female family member when she died. They made eye contact as she breathed her last breath, and saw a blue flash of light glow in her eyes and then leave her body. I was wondering if anyone has experienced a similar thing, or if this blue light can be explained by physics?

So for a geek convention coming up in a few months I was... considering dressing up as a cartoon animal. (Been going a little too mundane with my prior cosplay and wanted to make up for lost time.) But I'm worried about being too warm in it, so I want some sort of coolant between my outer costume and inner clothing. Icewater, I presume, would be a little too drastic and probably result in frostbite, if not hypothermia. (Even if I found a material watertight enough to make it work.) However, is there any other coolant whose equilibrium temperature is a little more comfortable; not too hot, not too cold?

Good day. Cut a strip of thin iron sheet (a coffee can after surgery by scissors) Say 25mm x 100mm x 0.5mm. Cover sharp edges with some vinyl-electrical tape. Wind maaany turns of fine wire coil from left towards right and keep winding back towards the starting point. Both coil ends are at the same side. That is sort of a Rogowski coil, with a flexible metal core. -I think- Now wrap the bendable strip coil thing onto an AC current carrying wire as the lower sketch. Will the winding present some voltage proportional to the big wire current ? -Ignore the decorative print at lower right-

So I was recently watching this video on YouTube and it shows a bunch of large balloons being popped in slow motion. (First example a few seconds shy of a minute in.) I can't tell whether that is dust or mist or something else at the outer edge of what used to be the balloon immediately after it was popped. Could the act of popping a balloon cause enough adiabatic expansion to bring the air in the immediate vicinity of the balloon to the dewpoint? Would the remnants of the balloon be aerosolized to the point of initially being visible as dust in the aftermath of the popping? Or is it a "little from column A, little from column B" solution with the aerosolized balloon bits…

Was trying to find hardness figures for nylon, delrin, ABS, teflon, poliethylenes ... and got lost in too many scales Shore, Brinnell flavors, Vickers, Rockwell, and metric and not metric, Is so much variety needed ? No consensus ? Very nasty to see so many and looking for the proper conversion. 😱

As a chemist, I am struggling with this. In, say, a helium nucleus, the rest mass is less than the rest mass of the "free" neutrons and protons from which it is made - the so-called mass defect. That makes perfect sense to me because, to separate the nucleus into its components, you have to do work against the strong nuclear interaction that holds the nucleons together, i.e. an energy input is required, which of course is then reflected in a greater rest mass of the separated nucleons. And hence the converse occurs during fusion, leading to a net output of energy when the nucleons combine and become bound. But when it comes to the quarks that form a proton, say,…

Good day. Let me know if I learned it right : The color of the lens is the color of a laser the goggle does NOT protect. The color of the lens is the one the laser beam color can pass trough. The protection from a laser is by reflecting, absorbing or blocking the beam and which of the three cannot be told by the color of the lens. Goggles can protect against several laser wavelengths except the one of the lenses.

Recently I saw comparison between an image taken by Spitzer and an image taken by James Webb space telescope (here, for example: https://www.planetary.org/space-images/spitzer-vs-jwst-in-infrared ). Why there are those rays of light visible around bright starts on the James Webb image (but not on the Spitzer image)? BTW, Is there a specific English term for this effect? Also, does anybody know what could be the exposition time needed to make these pictures (both, Spitzer and James Webb)?