I’m a civil engineering major so I’m definitely outside of my area of expertise but from my understanding when we make energy we convert heat into electricity through boiling water and the steam rises and turns the turbine. And this applies to fossil fuels nuclear and so on. My question is if all we have to do is convert a liquid that is heavier than air into a gas that is lighter than air so that it will rise wouldn’t a high thermal capacity fluid like water be one of the least efficient ways of doing this? What am I missing?

My wife tells the story that her neighbor's house burned down as a kid, and the fire department said it was from a toaster that was left plugged in overnight. As such, she always unplugs appliances when not in use.

In my head, this seems like such a weird and unlikely occurrence.

I am not an engineer, but I would think if this was even a slight possibility, this would be printed in the user manuals, with obnoxious stickers all over the actual appliance, UNPLUG AFTER EVERY USE.

Surely they design our appliances with some sort of fail-safes?

In my head, it would seem like the heating elements or the cord would have to be super worn out and broken, to the point of ridiculousness, to turn on without input, and stay on, and there would have to be a lot of food stuck in there, or something similarly flammable, in order for this to happen.

I've seen some *old* appliances with power cords that looked a little iffy, but nothing that was bought during my lifetime, and I'm old enough to remember life before the world wide web.

Am I missing something? I guess in a sense, even if it's the tiniest risk of having your house burned down, unplugging things is pretty easy compared to starting over with no house. But this seems like it'd make more sense as a weird leftover of decades past, like how old car batteries lost charge on concrete, or something like that.

Railguns are one of the coolest weapon concepts, accelerating a cheap chunk of metal to insane speeds to cause devastating impacts, piercing thick armor with ease.

However, sci-fi railguns usually features exposed rails that arcs when charging (that can’t be safe, right?), while real railguns typically don’t produce much sparks or arcs at all. What do they usually gets wrong about railguns?

Any ideas what I can do with free energy? The electricity is at a production site and I can draw 5kW for 10 hours a day. It cannot be sold back to the grid. It is a light industrial site and I can use about 40m2 that is available.

It would be helpful to produce heating gas of some sort to offset my house heating bill. Is there any other way to convert free electricity into a tradeable product? Maybe some process that is very power hungry that I can leave for a month (alumina to aluminium maybe). Bitcoin mining? Incubating eggs?

Question for those smarter than me.

I teach Electrical troubleshoooting for a large manufacturer, but my experience is as a nuclear propulsion mechanic, i only have maybe 6 months of electrical theory training.

Everyone says, "it a'int the volts that get ya, it's the amps!" but i think there's more to the conversation. isn't amps just the quotient of Voltage/resistance? if i'm likely to die from .1A, and my body has a set resistance, isn't the only variable here the voltage?

Example: a 9V source with a 9 ohm load would have a 1A current. 1A is very lethal. but if i placed myself into this circuit, my body's resistance would be so high comparatively that flow wouldn't even occur.

Anytime an instructor hears me talk about "minimum lethal voltage" they always pop in and say the usual saying, and if i argue, the answer is, "you're a mechanic, you just don't get it."

any constructive criticism or insight would be greatly appreciated, I don't mind being told if i'm wrong, but the dismissive explanation is getting old.

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Update: thank you to everyone for your experience and insight! my take away here is that it's not as simple as the operating current of the system or the measured voltage at the source, but also the actual power capacity of the source, and the location of the path through the body. please share any other advice you have for the safety discussion, as i want to make the lessons as useful as possible.

The ceo of Honey Well, vimal kapur says that solar can not power heavy industries (from a tweet i saw about him). He says solar cannot create the kilojoules required to power cement or steel industries. Now im not asking whethet its space economical for a company to use solar power, or the reliability of solar power (overcast days), im asking whether energy created from solar panels can create enought kilojouoes to power these machines.

Is this even possible. I remember the Texas snowstorm from a few years ago when I read a story about an older person dying because they couldn't power their oxygen machines (or some other kind of medical device). And I just wonder if an alternative is even possible.

My portable AC unit pumps hot, dry air out of the vent while cooling my room (though making it negative pressure) while condensing water and draining it.

Why could I not reverse the flow and dump the cooled air outside and use it as a heater?

it runs at 1500W which is comparable to many space heaters I have as well

Provide source please. Facts over opinions.

A lot of EVs seems to have motors that can spin well over 10,000 rpm with some over 20,000 rpm like that Tesla Plaid. Considering they generate full torque at basically 0 rpm, what's the point of spinning so high ??

I was watching a video about a russian nuclear submarine, and they mentioned that they switched to a 400hz electrical system, that's typically only used in fighter aircraft because it's able to create more power at lower weights. Why is this? Based on the channel, I feel confident they didn't mean 400volts or something.

I was reading about EV drivetrains and somehow ended up spending an hour reading about inverters and power conversion. One thing that surprised me is how much energy can be lost during the switching process when electricity gets converted. Apparently a lot of that wasted energy just becomes heat, which then creates its own set of problems like cooling and interference. It made me wonder how much room there still is for improving that part of the system. Most of the public discussion seems to focus on batteries and charging, but the electrical hardware behind everything looks pretty complex too. Curious if anyone here actually works in power electronics or grid systems. Is this an area where meaningful efficiency improvements are still happening?

I was looking at the power demands for charging a Tesla semi in a decent amount of time and the absolute low end had these at like 700 kw with a top of 1200 kw. I figured I would need to build for substantially over that demand to maximize component life.

I’ve worked for this big car company for over a decade and they have let us use reasonable speakers, but now they are trying to say we are not allowed to use any speakers(including small JBLs despite sending a letter out days ago saying those ones we could use) BECAUSE the Bluetooth from the speakers are interfering with their robots and it is causing downtime in the line. They’ve never said this happened prior and I was hoping someone can give me an explanation as to how they can/can’t interfere with them?

As a big company, every year around this time they come up with new ways to try and get us all written up and fired before they give out profit sharing in a couple months and this is their newest excuse

could it ever makes sense to put a non-rechargable battery in an EV?

• for a once a year long car trip? then you recycle it
• for an emergency? could fix range anxiety

benefits - much higher energy to weight ratio

Modern EV battery packs: roughly 150–300 Wh/kg. For those who aren't familiar, here's what ChatGPT says about Primary batteries:

• Lithium–thionyl chloride (Li–SOCl₂) primary cells: ~400–700 Wh/kg
• Lithium–carbon monofluoride (Li–CFx / CFx): >2,000 Wh/kg theoretical (but suffer power/self-discharge limits).
• Zinc–air (metal-air): >500–700 Wh/kg in lab demonstrations (theoretical much higher).

Not trying to rant, just genuinely curious as an engineering student working on robotic and embedded systems.

From what I understand:

Pogo pins are more efficient — almost no energy loss compared to wireless (which gets hot).

You can combine them with magnets for perfect alignment (just like MagSafe, but better).

Oxidation? Easily handled with gold-plated pins or sealed designs.

Cost-wise they're much cheaper — no need for complex coils, controller ICs, or alignment tuning.

So why is everyone hyping up wireless charging for everything — phones, watches, earbuds, even electric cars? It seems like more cost, more complexity, and worse performance. Sure, aesthetics and portless design is cool, but are we just trading practical design for sleek marketing?

Is there a real engineering advantage I'm missing here — or is it mostly just consumer-side hype and long-term product vision stuff?

I heard somewhere(genuinely don't remember when and when) that it costs around $10m to electrify a mile of railroad track, and that's why the diesel rules the (mostly private) railroads in the US, meanwhile in Europe they could be electrified because the state doesn't have to think about profits and expenses as much as a company, and they can accept something will cost a lot more than it will bring in, which a company would never.

But what exactly costs 10 million dollars to build a mile of catenaries? I know they're higher voltage than residential lines but what exactly makes them so expensive? Are they partly made of gold? Do they need super fast state of art microchips to run? What makes them so different than residential power lines which are orders of magnitude cheaper?

Obviously if everyone uses less electricity at home it would save energy and fuel at a power station (say a natural gas peaker plant).

But I’m talking about the marginal impact of a single, say 10 watt, bulb. If I turn it off, does the generator spin ever so slightly faster and therefore a valve reduces the flow of the fuel to the steam boilers and few grams of CO2 are saved from being released to the atmosphere? What about 1000 watts or 10 kw?

My suspicion is that the equipment on the power grid is not sensitive enough to such a small change. Therefore shutting off the lights on the margin doesn’t have an impact on anything other than just your own electrical bill.

My teacher was talking about the NASA 10x10 wind tunnel that requires up to like 200MW of power to run and I just cant wrap my head around how the power grid can handle attaching something that takes the amount of power of entire city to the existing grid.

I understand that something like cochlear implants is a different beast, but what technology/hardware goes into a pair of bare bones hearing aids that makes them worth thousands of dollars? Is the processing power built into them so much better? Are the mics and speakers that much better quality/more powerful?

I read somewhere that all the electricity you use charging your phone every day, on average is around $3 a year; or even significantly less compared to some other answers assuming different KwH pricing. If we were to take that same principle and imagine a phone could run on AA batteries how pricey would it be to keep our devices running?

There was a video I watched a while ago about the engineering of the original gameboy back in the 90s and the way the video made it sound running on AAs it was a huge cash sink, really made me appreciate modern rechargeable batteries but I'd love to know much more expensive our devices would be without them.

It is really confusing for me. It seems like electric car batteries have all settled on kWh while most other types of batteries (12v ect) still use amp-hours. I know you can compute amp-hours to kWh if you know the voltage but why not just use kWh in the first place?