Yeah both the monitors and computers will consume a bit. Even a modern PC when turned off is in a type of deep sleep mode, for stuff like wake on LAN.
The chargers will hardly even register anything, except maybe in some rare case where its a special one that is doing some sort of passive listening (like the PC’s)
A funny culprit I found during my own investigation was the GFCI bathroom outlet, which draws an impressive 4W. The status light + whatever the trickle current it uses to do its function thus dwarfs the standby power of any other electronic device.
A good rule of thumb is that the energy needs to go somewhere. So if the adapter was drawing a significant amount of power, it would get warm to the touch.
That’s true - And with a halfway decent thermal camera, you can see most of these unused chargers as “hot” spots. They’re so low power that they’re only slightly above ambient, but still something the cameras can see.
That’s how I found out that my desktop speakers consume power even with the physical button being off and status light dark. The power brick stays warm indefinitely, a good 20W feels like! I have to unplug that thing now when not in use. Any normal power brick will be <1W of course.
Depends on the charger but either effectively zero or considerably less.
People get pissy about it, but think of electricity like water. Having a longer pipe is a negligible amount of water if the faucet is still off. And the faucet can only turn on if your device completes the circuit by being plugged in (and doing the appropriate handshakes)
That said, some chargers will consume a negligible amount of electricity to actively listen for a device. Think of it like the water in your toilet. Every so often enough evaporates or leaks that you hear it run a bit to refill. But mostly it is nothing until you flush.
I use a short lightning cable to plug my phone to my car for carplay. I just leave it plugged into the usb port (without the phone) when I’m not in the car. Do you think it’s slowly draining some energy from the car battery?
The cables themselves do not use power. It is the brick.
Your radio being off would not push any power through a cable. Also your cigarette lighter being off would not push any power. Which is why plugging it in won’t do anything.
To continue the metaphor - your water is turned off. You can’t use up water that isn’t there.
The reason the brick uses power is because it is available 24/7 for you to plug something in - and when you do - it can ask that device how much power it wants - does it have fast charging? Etcetera.
Thanks. About the cigarette lighter - my dashcam plugs into it but I always unplug it before I turn the car off so never noticed if the camera turns off along with the car. If it does, does that mean I can just keep the dashcam plugged in and it won’t draw power even though the camera is connected on the other end? Or does closing the circuit mean it will start drawing power?
The water analogy is perfectly fine for many situations, but the reason these don’t draw a lot of power when nothing is plugged in isn’t because a “valve is off”. There’s a transformer, so this is like two separate water lines. If the charger is plugged in, there’s always a closed circuit on the mains side of the transformer, even if there’s an open circuit on the DC side. See the first diagram here: circuitdigest.com/…/ac-to-dc-converter-circuit-di….
The reason new chargers don’t use as much power with no device attached is because of better design. If you checked an old charger or some crappy power supply, they’ll use a fair bit of power even with nothing on the DC side. It’s not enough that one would matter, but it is enough that there was an industry wide initiative to reduce phantom load resulting in new chargers that use almost nothing when nothing is on the DC.
Well, g is not a real constant, it depends mostly on altitude. The true constant is G. g=9.8 is usually more than enough for your calculations, to the point we often round it to 10 for simplicity, or you remove it completely is the mass is too low. But actual numbers is only the very last step usually. The calculations will be made with letters. The value you use at the end for g depends on the precision you need, so it depends on the precision of the other parameters.
Just don’t make the same mistake as one physics lab did. They made a series of measurements and their results showed that gravity quickly increases in fall, falls slowly over winter, and back to about pre-fall levels very slowly in summer. It took quite a while to figure out the reason of this unexpected result. They turned their equipment inside out to find a mistake to no avail. Then they realized that the university stored coal for the central heating and hot water in the basement under the lab…
I’m assuming they’re indicating that the mass below the apparatus increased in fall (when storage was filled) and decreased slowly through the winter, leading them to measure a changed graviational constant. A back of the napkin calculation shows that in order to change the measured gravitational constant by 1 %, by placing a point mass 1 m below the apparatus, that point mass would need to be about 15 000 tons. That’s not a huge number, and it’s not unlikely that their measuring equipment could measure the gravitational acceleration to much better precision than 1 %, I still think it sounds a bit unlikely.
Remember: If we place the point mass (or equivalently, centre of mass of the coal heap) 2 m below the apparatus instead of 1 m, we need 60 000 tons to get the same effect (because gravitational force scales as inverse distance squared). To me this sounds like a fun “wandering story”, that without being impossible definitely sounds unlikely.
For reference: The coal consumption of Luxembourg in 2016 was roughly 90 000 tons. Coal has a density of roughly 1500 kg / m3, so 15 000 tons of coal is about 10 000 m3, or a 21.5 m x 21.5 m x 21.5 m cube, or about four olympic swimming pools.
Edit: The above density calculations use the density of coal, not the (significantly lower) density of a coal heap, which contains a lot of air in-between the coal lumps. My guess on the density of a coal heap is in the range of ≈ 1000 kg / m3 (equivalent to guessing that a coal heap has a void fraction of ≈ 1 / 3.)
Can’t be that big, as the difference in mass close to the instrument only varied in the several tons category, but obviously enough to puzzle the scientists.
Close enough I graduated last year 2023. I couldn’t get in to the college I wanted so I decided to try it a second time. There’s a countrywide exam that gives you a score. It’s called yks. I’m currently studying for that exam.
Rounding of constants always depends on what you are calculating. Getting a rocket into orbit is a case to use the actual local value of g with a bunch of digits (and the change with height, too). If you build a precision tool, some more digits of PI are no bad idea.
But to calculate the lenght of fence to buy to surround a round pond, I actually used 10/3 for “PI plus safety margin” once.
In grade school i learned it was about 32 ft/s2, but by high school on it was all 9.8[1/06] m/s2. Then in engineering school it was sometimes 10. None of that had anything to do with local gravity and everything to do with Americans having to be special at first, followed by the fact that our science classes are actually in metric (statics and dynamics were in both as some fields of engineering haven’t metricated yet here). And the 10 is because you can round to a round number by barely even touching your fudge factor so why not.
I was going to say that even here in the US it was 9.81 m/s^2. I don’t remember ever being taught the number in feet (in NYS) nor seeing it for my kids (in MA). Science was always metric
Ohio, and Catholic schools. It was clearly on its way out. In retrospect it was definitely a strange situation where different teachers had different opinions on metric. Some clearly thought it’s fine for science, and others clearly just wanted to quit our two measurement system that does nothing but prolongs the inevitable.
G is the gravitational constant, the m’s are the masses in question, and F is the force generated. The r is radius from the center of one body to the other; that is, height. If it didn’t decrease, orbits wouldn’t exist the same way and astronomers would have laughed Newton out of the room.
I could give you a link if you really want, but it’s the Newtonian gravity equation, so it’s probably just going to be “Gravity” on Wikipedia.
G is also fixed in GR, although it’s not guaranteed to manifest in a neat relation like that in every situation because spacetime curvature has a lot of components at every point, and they interact super nonlinearly.
This doesn’t change the issue presented by OP. Sea level is not level across the world. In fact there are much larger differences than most people expect. The Earth is not perfectly round. Earth rotation causes the equator to be affected by a centrifugal force, making it wider there ( more distance to earth core means less gravity ) than at the poles. Overall, gravity at Earth surface level varies by 0.7%, ranging from 9.76 in Peru to 9.83 in the Arctic Ocean, but it’s absolutely not linear. In addition, the Earth is full of gravity anomalies. These cause localized dips and spikes in gravity. Two of the big dogs lips lie in the Indian ocean and the Caribbean. Because water is fluid, sea level is very much affected by local gravity (as well as other factors such as air pressure, salinity, temperature…). Which is also why the moons gravity can cause tides. The permanently lower gravity on these anomalous spots mean that the average sea level here is lower than it would be on a perfect sphere. This difference can be up to two meters in sea level.
we learned it was about 9.8. We actually measured what it was near our school, and I think it came out to 9.82. We were told it was ok to use either 9.8, 9.82 or 10 in exams.
askscience
Newest
This magazine is from a federated server and may be incomplete. Browse more on the original instance.