Engines: Crash Course Physics #24

Engines: Crash Course Physics #24


One of the greatest inventions is the steam engine. But why? What makes it so useful? And how does it work? In this episode of Crash Course Physics, Shini talks to us about how engines work, what makes them efficient, and why they’re pretty cool.

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100 Comments on "Engines: Crash Course Physics #24"


  1. I really like that y'all have the Giancoli book. I mean, idk if y'all use it but it was my favorite physics book and I feel an extra connection now.

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  2. There's way too many jump cuts please cut those down only a person with the attention span of .5 seconds needs those. For the rest of us it's just annoying and choppy

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  3. I feel that even though she's speaking very fast I can still hear that she has a accent, like she is British or something

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  4. The graphics have a copy editing problem. Several times, including the first, Q sub H is captioned as "input temperature" not "input heat".

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  5. I found a little bit confusing the explanation about the reason of isothermal processes in carnot cycle.. It's isothermal to favor reversibility?? It does not make too much sense, because the heat transfer is with the hot source and cold sink not within the cycle… I mean there is indeed a temperature difference between the hot source and the hot isothermal process, the only fact that maintain the process isothermal is that it's doing work at the same time that it absorbs heat… Other remark is that the T-s diagram is more apropiate to understand heat engines cycles and it efficiencies (just need to spot the ratio between the area under the cold curve and the area under the hot curve)

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  6. That diagram at 1:42 is almost exactly how your house gets electricity (unless your grid is fed by solar or wind). The power plant uses coal, natural gas, oil, nuclear fission or even garbage to create heat in what they show as the boiler. Then just replace that piston with a steam driven turbine that turns a big generator and boom, your house has glorious power.

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  7. Where would electric engines stand? They start off with ambient heat, max torque at 0rpms, output heat is significantly lower than a steam or an IC engine, practically all are reversible.

    (Edited to fix auto correct errors)

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  8. steam engine coal pollution advance. Right. Half an advance maybe, but what about the environmental cost? More inventions were needed to combat that.

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  9. Brains & Beauty. She's easily smarter than I am, and I've tested in the 95th percentile before. Prolly better looking too.

    I think I'm in love.

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  10. Only with me or there was an issue with the mic in this video? There is a high-frequency "shhh" in her voice I never heard in any of the videos before o.O

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  11. Off topic of the contents of the video … sound editing seems a bit off, as her 'S' (or soft 'C') are very harsh and cutting, as if that frequency was amplified or something.

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  12. This was way too much information to put into one video. SRSLY.

    The other problem is that you didn't even go into WHY the Carnot engine is maximally efficient. Maybe some historical context on why Carnot even bothered to figure this out might help…

    Third, I think it's important to explain that regardless of the type of engine. Any engine that converts heat into mechanical energy will be limited by the Carnot Efficiency, I believe there is a relevant quote from Carnot about this.

    Maybe also include a primer on what a heat engine is and why we care…? Abstract away the details and show the simple model.

    You can't just talk fast, and expect people to understand. This is absurd. It's one of the most important and interesting topics, and you're just glossing over everything.

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  13. its sad how the outtakes prove she is just reading off cue cards. she has no real understanding of what shes talking about.

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  14. How about demonstrating an actual functioning design rather than theory. I would like to be able to build an engine not theorize about one.

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  15. Thermodynamics? Um, I think it's safe to say this whitewashing of industrial history is offensive. It's a good thing I'm a youtube hero otherwise this wouldn't have just been flagged for sexual lyds explicit content or whatever I just flagged it for.

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  16. I think that this is ' to mathy ', show the engine first and then explain the principles and then do the math.

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  17. Wonder if you could replace a steam train coal kettle by a radio isotope thermo-electrical generator, new age steampunk stuff 😉

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  18. Damn it! I cannot believe this… I am racist but can we get another host in here?! Like a robot, or a puppet, or a duck…why human?

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  19. Can any one help me with this problem my physics teacher wants me to do.

    Problem) he wants us to remove water from a sealed jar, but we cannot remove lid, put holes in any part of the jar, tilt the jar, and must be done with house hold items, and he said he wanted it done 'now', so i'm assuming i can't just wait for the water to evaporate. ps) the jar is full of water.

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  20. sorry, didnt wait till the end. I checked the description… none of the info there. got the host in the credits, ill do the research

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  21. I'm doing a degree in physics. We have t covered this yet and I find this confusing. I really only think people enjoy watching these videos if they already understand the topic. I don't think that crash course's style is at all suited to physics

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  22. Just wondering,is the 4 stages of the Carnot cycle somehow related with both the diesel and petrol engine compression and combustion cycles?

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  23. Is there a quantity to describe how well a real engine compares to a Carnot engine working across the same temperature range. Like actual efficiency/Carnot efficiency

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  24. I spent an hour this morning reading about thermodynamic engines from a Physics textbook and still had trouble understanding. Then I watch this 10 minute video and immediately understand what's going on.

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  25. Thanks! The production value is great. However:

    At 05:00 you say that there is an isothermal process where heat is slowly added, but the animation shows lots of heat (Q_H) escaping. What gives?

    At 05:04 You say that the isothermal expansion is 1/2 AB. Shouldn't it be the entire path AB?

    At 05:15 you say "the temperature drops whilst the heat stays constant, which also makes the volume expand". Well this is misleading: a temperature drop would cause an isolated system volume to contract. However in a Carnot engine, the system is doing work on the atmosphere, converting internal energy into work, and dropping the temperature. It's best to say that the expansion work drops the temperature, not that a colder temperature causes an expansion.

    Also, when you keep saying "the heat stays constant", shouldn't you be saying "there is no heat flow" or something equivalent?

    At 05:40 you say "the heat doesn't change" but perhaps you should be saying that there is no heat flow, or the system is thermally insulated, or something else equivalent.

    The way you explain it sounds as if heat is a state property, when it's not.

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  26. she fitted all engineering and technological/industrial applications of thermodynamics of the last episode in less than 10 minutes…. too much information for a small amount of time = she spoke fast… as if she;s on a hurry….. …. now I knew that steam engines and refrigerators are machine cousins… 🙂

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  27. before my summer vacation they were exactly sincronised with what i did at school. in the vacation they we don't do, so it's perfectly sincronized now too :)) helps me a lot, as this year we have a bad teacher

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  28. Compilation Guy>>>> And I need a crash course on basic gymnastics and acrobatics that covers front- and backhandspring, front and back somersault, aerial, side-somersault and handstand.

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  29. Shini, do you play Magic The Gathering? The new set, Kaladesh, is about invention and is inspired by India. I have a sense you will really like it.

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  30. I'm a simple engineer
    When I see girl do thermodynamics I love her.

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  31. you sound lovely but it would be a lot better if you could slow down a bit. improved understanding!!!

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  32. you know, if you think about it you could in Theory build a stream powered refrigerator

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  33. pro tip to watching these fast videos: pause between sentences to mimic a realistic conversation and time for your brain to understand what she just said.

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  34. The animation of a refrigerator at work is completely reversed and incorrect: after the liquid is turned into a gas it is compressed at which point it flows to the condenser to shed the heat extracted in the fridge(and the heat generated by being compressed) and return to a liquid. This liquid is then sent through an orifice or long, thin capillary tube so that it pressure is reduced hence it's temperature lowered. This liquid then goes to the evaporator inside the fridge where it absorbs heat from the interior and boils into a gas before returning to the compressor. The animation shows the compressor as a "decompressor" or expansion device(orifice, capillary tube) and that is opposite of it's true function as the whole thing is reversed.

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  35. I'm a mechanical engineer that's passed the thermal and fluid design PE exam, and i found this video helpful as a reminder of the basics! Thank you

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  36. These videos are good overall, but that's just an awful description of how a refrigerator works. She doesn't even mention the pressure difference in the two halves of the loop.

    Also, all you young'uns with working high-pitch hearing need to learn how to use the equalizer on your computer or phone.

    Reply

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