I really wanted an intuitive feel through experiments, but unluckily i dont have access to them. Really appreciate these lectures, although old are really informative and entertaining. THANKS
This lecture with early models of thermostates made me realize that temperature scales are artificial and arbitrary, and not always precise. Makes one a little relativistic and existential
Greetings sir, I'm from India. Sir, a very basic question that many students are afraid to ask, even I'm a little bit " If we want to start developing something new from the very beginning, what should be the core idea to keep going?" Thank you so much sir for providing these lectures where students can think extraordinary. Regards.
Professor Lewin, do you have any suggestions on how I can make my own "amplifier" like the one you used for the thermal expansion experiment? I was fascinated by how you used the pivot in order to amplify such a small amount of expansion. :)
Professor Lewin recommended the book - *Physics for Engineers and Scientists - Ohanion - Vol 1* And, The Assignments for each group of lectures (with solutions) are available in the description of all videos.
@lectures by walter lewin Sir, I can't exactly figure out what we mean by temperature, i suppose the magnitude of jiggling of atoms of a substance at macroscopic level is sensed as temperature and the same jiggling atoms when they pound against a wall the averaged momentum transfer is felt by us as pressure my question is most knowledgeable people wright in books , we can't achieve 0K thermodynamic temperature as it's impossible to seize the motion of atoms completely. Well i have a way around it in this big intersteller space let's assume there is a place where no radiation is present yet then why zero kelvin can't be present there there we don't have to deal with seizing of atomic motion as we are no longer dealing with atoms or matter , so is it that in space 0K is possible but matter can't be manipulated to completely loose it's motion then 0K is observable thing and not a impossible scene .
I think Professor Lewin has pointed the way for on line demonstrations to be adapted to the TEACHING of Science and the humanities. The practical that are to be assessed could to be in schools or at special centres.
thermal expansion on heating basically occurs because of the due rise in temperature results in increased amplitude of oscillations between atoms of a material so the average sepration between them increases. My question is that in most textbooks rod is shown to expand only in one way, while in reality, it should expand on both ends in opposite directions?
rods expand in all directions, if the length is 1 m and if the extension is 0'.1% then the rod expands by 1 mm. If the radius is 5 mm, then it expands by 0,005 mm which is 5 microns
Sir thanks a lot for clearing my concepts...i am a hosteler and am returning back to my hostel where i cant be under your guidance....thanks a lot sir...wish a wonderful happy birthday and God zegene je
Do you have any book of yours, or any book you can prefer me to study, im in 11 th grade in India, and am preparing for NEET(hope you can google that). Well you're my mentor.
Lewis sir I m just loving u more more nit just as a physics but as person I owe u so much Obeisances to u alma mater….May you live long and stay Happy always …Really wish I had aptitude a chance to be there learning from u in MIT …..Next birth for sure
@@lecturesbywalterlewin.they9259 Sir where can I get all ur lectures and also I really wanted guidance to pursue astrophysics and physics I m 34 yet I wann to do it I i m an engineer could 7 please guide me through
@@anubhaagarwal4224 Watch all my 94 MIT course lectures. Start with 8.01, then 8.02, then 8.03. Do all the homework and take all my exams. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam* You will find all information you need on this channel (notice the three playlists "Homework & Solutions"). 8.01 & 8.02 will each take about 200 hours, 8.03 about 250 hours.
@@lecturesbywalterlewin.they9259 sir I m doing tht hv already begun but do u think me being 33 now if I wann I cn genuinely get thru some very good university and do wonders in physics and astrophysics
Sir in an atom electrostatic force btw e and nucleus act as centripital force, but why that happens only in atom but not in isolated proton and electron?
Greetings Sir, Does your book For The Love Of Physics contain contain theory to understand the topics or is it an entertainer? I like your way of teaching and would surely want to buy the book if it has theory to build up my concepts for various examinations. please help me out with one more thing, is there a chapter on Thermodynamics? Regards.
+Shivam Agarwal Other substances that expand on freezing are silicon, gallium, germanium, antimony, bismuth, plutonium and also chemical compounds that form spacious crystal lattices with tetrahedral coordination.
20:56 I found the answer to be 1mm. The formula that I used is R = 2d(1+α_2·∆T)/{(α_1-α_2)·∆T} and θ = l(α_1-α_2)∆T/(2d). These gives ∆h = R(1-cosθ) = 1mm. Please tell how to proceed to the correct answer.
Sir really like your lectures. sir I have a question from calorimetry. In the latent heat of water will the specific latent heat increase or decrease with the change in pressure? I have a confusion since water at low pressure boils below 100 celcius so will the latent heat always remain same?
If the material is uniform, then, the volume will change with temperature but not the shape. Thus the expansion between any 2 random points will be linear. use google
sir, I have always had a doubt that, on discussing with my physics faculty, is always dismissed. If we take a concave hole, i.e. like a rectangle that had one side bent inward. If we make a hole of this shape on an aluminium sheet (2D), will the areal expansion cause the material to move into the hole or away from the hole? Will the convexity of the material affect the direction of expansion?
If its concavity is high, then there wont be enough area for expansion resulting in bursting. Similar to wine glass which is highly concave will burst if heated too much.
Sir at 20:25 I am getting the vaue of d to be 2mm and not 4mm. Sir I used formula thickness × angle of arc= difference in delta l. This gave angle of arc. Using this I found radius of inner circle. Then deducted radius × cosine of angle of arc from radius. Which gave 2mm. Please clarify.
Now I'm in 11th std, Sir I want to ask you that should I opt for IIT or should I do Bsc,Msc and Phd in physics and a difference is for bsc in physics we don't need entrance exams as for iit is. what should i choose ? can you advise?
The fact that America still uses imperial measurements is a sad bit of politics. Specifically, in the United States we officially switched to SI in 1975, but we didn't fund the transition. President Ford created a board to coordinate the transition of the United States to SI, but the board was abolished and all the progress halted by Reagan even though the law is still on the books that says we should be transitioning. The United States officially uses the metric system as "the preferred system of weights and measures for United States trade and commerce" but conversion is voluntary and no funding is in place.
I have a question. Assume that we have some mercury of V0 volume at temperature T. I increase T by an amount of dT. At T+dT, I have V1 = V0 + dV, where dV = V0*beta*dT (Eq. 1). Now I decrease the temperature from T+dT to T, I have V0 = V1 + dV, where dV = V1*beta*(-dT) (Eq.2). Now, I take the absolute value of dV, then I have dV = V0*beta*dT = V1*beta*dT. However, V0 is not equal to V1. I should be wrong somewhere!!! The only way I can explain it to myself is that beta depends on the temperature.
I know its too late but if anyone else is interested (and since this is actually a good conceptual question) the assertion that change in volume when heating is equal to negative change in volume when cooling is wrong. If you think about it it's like with railways thing that was presented here they bent on a scorching day and stayed bent on cooler days the linear expansion wasn't equal in both directions.
sir I do have a doubt that in my 11th std textbook under lesson thermal properties of matter they've given relations between Beta and Alpha in ther it is Beta = 2 Alpha where you say Beta = 3 Alpha ( 34:19 ) sir please tell which is correct.
@@lecturesbywalterlewin.they9259 sir my texbook of 11th std is of maharashtra board of India, and in there it says under the topicrelation between co-efficients of expansion, relation between beta and alpha, and it's result is- "since the values of Alpha are very small, the term - alpha^squared ×T^squared is very small and may be neglected. Therefore Beta = 2Alpha "
sir for even if i write 2 alpha in exam for a situation but i want to know in fact or according to till now proven theories on heat, what will be the real value - 2 alpha or 3 alpha
Temperature was defined such that it depended linearly on change in length of the mercury column. So that is how it was defined. We measure the change in length of mercury as it goes from 0°-100°C and divide it into 100 equal lengths, each corresponding to a particular temparature. So why is it that for all materials, one degree change in temperature corresponds to same change in length (for a material of given length)? I know it seems obvious, but I can't come up with the logic myself. I'm getting stuck here.
>>>>>So why is it that for all materials, one degree change in temperature corresponds to same change in length (for a material of given length)?>>> NOT TRUE
Thank you very much for responding prof. But why isn't this fact covered in any of the standard physics textbooks ? even the differential equation isn't hard to solve at all for a calculus based course
During heating ,In the bimetallic coil how can one know that which metal is on the inward side or outward side? What are the different forces acting on the bimetallic coil during the heating?
metal 1 and metal 2. Metal 2 has a larger expansion coeff than metal 1. If we add heat metal 2 will get longer than metal 1 thus the bimetal will coil up with metal 1 on the inside of the coil.
Sir i tried to find the answer in Google as well as in many Indian high school physics books (as I'm an Indian high school student ) but none of the above mentioned sources is providing a clear concept. sir pls help...I'm really stuck in these radiation related terminologies.
Hi professor. Regarding this lecture, how about if we go down below 0 degree celsius for water at atmospheric pressure(pressure not changing). It will still expand or not? Thanks.
my answer was wrong. there is no capillary action between mercury and glass. Here is the correct answer which I found online. "A thermometer tube interior cross-section is quite small … usually about 1/8 inch or less (the curvature of the glass has a magnifying effect, making the mercury column seem bigger than it actually is). Mercury does not react or even adhere (“cling”) to glass. The mercury column holds itself together by surface tension. However, if the glass tube is wide enough that the weight of the mercury is greater than the retaining effect of the surface tension, then the mercury will flow downwards abruptly. And remember the old-style hospital thermometers: it took several very brisk shakes of the inverted thermometer to force the very thin column of mercury back down into the "
I have a question that has been kind of in the back of my mind bugging me for a long time. Say I have a circular plate of metal, and a perfect square is cut in the exact center of the plate. If the plate is heated or cooled do the sides of the inscribed square retain their perfect straightness or will they expand and contract an curve just a little bit?
Please😭 , if anyone knows the solution to the problem mentioned at 20:30 please reply ,am so so curious I couldn't solve it . maybe could you suggest a video with same concept
Heat flows from a hotter body to a colder body till the time both are at same temp. right? So that means if I have fever and I'm 100 F, then when I insert a thermometer, it will show me a lesser reading? Am I getting cooled everytime I insert a thermometer to check my temp.?
The natural temp fluctuations of your body are probably 0.01C on time scales of minutes and less. Your temp change when you measure your temperature is not even measurable as it is probably less than 0.000001C which is MUCH smaller than the natural fluctuations.
If you heat something enough ,state of that thing is gonna change....like if you're heating a metal.... eventually it's going to melt and become liquid, and on further heating- gas.
sir , i have a question not related to this topic but , i am going to ask anyway is the carnot cycle an internally reversible process or is it a totally reversible process, it should be an internally reversible process only as some net work is actually produced or am i wrong ? i am confused.
yes it's reversible, use google The Carnot cycle consists of the following four processes: A reversible isothermal gas expansionprocess. In this process, the ideal gas in the system absorbs qin amount heat from a heat source at a high temperature Th, expands and does work on surroundings. A reversible adiabatic gas expansion process.
I am surprised how you casually said that you overheated the mercury thermometer and made it explode. Wouldn't the exposed mercury be extremely harmful since it releases fumes?
Ice contracts the instant it freezes solid, and continues contracting all the way to absolute zero. The relation is not linear, and it contracts less per unit temperature the colder it gets. The highest rate of contraction happens right at 0 Celsius just after it froze. It does not become denser than water, given a pressure of 1 atmosphere.
sir i understand the concepts but i am not able to solve numericals ........... what should i do sir.............sir i am a iit jee aspirant.........pls sir need some guidance from you
sir, can u please tell that how exactly, any of the temperature scale was originally defined (or is currently defined). actually my doubt is - say for kelvin scale, setting absolute zero temp. as 0 K is fine, setting something at 273 K is fine, and now how this scale is divided? like if i wish to go to 15 K, how will i? the change in length of a material is a bad idea as one cannot say that it will expand linearly. sir, please don't ask me to ask google as i already did it.. :)
Sir sorry for pestering again. Could you tell me where the 8.01 lectures that you have mentioned can be found? (the ones in youtube are the 8.01x) And are they more detailed(I mean do they include the proofs)? Thank you for your lecture and kind replies Sir
My channel has my 8.01x and 8.02x lectures. The context is slightly different in only a handful of lectures from 8.01 and 8.02. Key is that the x lectures have a higher resolution than the non-x lectures which were originally on MIT's OCW.
Entropy is only conserved in the special case of reversible processes. Entropy is a property such that the entropy of the universe, will either increase or remain the same, but never decrease. If entropy of a system decreases, the entropy must go to another system. It cannot be destroyed.
sir,at last you explain the special character of water...and u gave some examples...about skating...fishes ...i didn't understand it clearly...can you please explain it to me again
Water is very special indeed. Ice at 0 C has a larger volume than water at 0 C, that's why it floats and that why we can skate. I watched and listened to what I said. I cannot add to it. Please use Google if you want to know more details.
Just up to calc II, but if you're in a rush, learn the basics of Derivatives, Differential Equations (1st and 2nd order), Integration, and Taylor Series.
You are politically correct - but that's not the way we speak. There are 3 temp units, Celcius, Fahrenheit and Kelvin. When my wife asks me what is the temperature I would ALWAYS say 55 degrees Farenheit thus I also say that in my lectures. In writing I would say 55 F. I would write 300 K but I would say 300 degrees Kelvin.
Energy is anything measured in Joules, that is a capacity to do work. Could be thermal energy, heat, work, kinetic energy, strain energy, chemical energy, etc. Heat is one particular form of energy, that is a thermal transfer of energy from a hot object to a cold object. The result is that one object gains internal thermal energy, and the other object looses internal thermal energy. "Internal thermal energy" refers to the molecular level kinetic energy within the objects, which could come in the form of translation, rotation, vibration, and in metals, the unorganized motion of the conducting electrons. This is why different materials have different specific heat capacities.
they are working but you do not know how to access them. For people like you I have made 3 playlists: "8.01 Homework, Exams, Solutions, Notes" similar for 8.02 and 8.03
Heat will flow every time there's a difference in temperature; (No temperature difference means no heat exchange); heat will only flow - and flow it will - from higher temperature to lower temperature. (lower to higher is not possible); heat is exchanged by 3 ways: conduction; convection; radiation. Don't confuse temperature with heat. (it's like tension and current). there are an immense amount of free books available on the matter.
The best part about these videos:-
I don't have to wait till the next friday😂😎
EXCELLENT....GOD BLESS OUR PROFESSOR.
I really wanted an intuitive feel through experiments, but unluckily i dont have access to them. Really appreciate these lectures, although old are really informative and entertaining. THANKS
i wouldnt say old it would say a legend
the clearest explanations in the world, those of Professor Lewin. Congratulations Walter, from an old doctor (cardiologist).
This was so fun
Didn’t feel time slipping away 😅
I wish i had a physics teacher like you
In US:- Enjoy your weekend
India:- Study hard on Sunday
What happened bro
27:47 Civilised scale :DD Laughed really Hard hahaha :D
:)
😂😂😂
This lecture with early models of thermostates made me realize that temperature scales are artificial and arbitrary, and not always precise. Makes one a little relativistic and existential
Greetings sir,
I'm from India. Sir, a very basic question that many students are afraid to ask, even I'm a little bit " If we want to start developing something new from the very beginning, what should be the core idea to keep going?"
Thank you so much sir for providing these lectures where students can think extraordinary.
Regards.
Why did you start the idea and what does it have an impact on your life and imagine yourself completing that task
14:04 the railway did not get warped due to a hot day,
It was due to the heat of friction between the train wheels and the railway track
@@Medcuriohub lmao your name cracked me open😂😂
my god he can teach every subject of physics very very v v v v v v nicely!!!!!!!!!!!!!!!
:)
Professor Lewin, do you have any suggestions on how I can make my own "amplifier" like the one you used for the thermal expansion experiment? I was fascinated by how you used the pivot in order to amplify such a small amount of expansion. :)
talk to an engineer and tell him what you want.
I can give you a better answer..... Google search.
amplifiers are hard and people often keep them secret. my suggestion is transmission is easier than amplification and u should try that.
The coolest physics professor!
thank you
Sir, thank you so much, for these interesting lectures on physics.....
This professor .He's really make me to fell in love with physic
the only physics teacher who inspired me..i need mcqs of physics. do you sir?
:)
What textbooks are used for the assignments for all your lectures? Are they still available?
Professor Lewin recommended the book - *Physics for Engineers and Scientists - Ohanion - Vol 1*
And,
The Assignments for each group of lectures (with solutions) are available in the description of all videos.
Inference: Anything that reacts significantly to small temperature changes, is a good thermometer.
@lectures by walter lewin
Sir,
I can't exactly figure out what we mean by temperature, i suppose the magnitude of jiggling of atoms of a substance at macroscopic level is sensed as temperature and the same jiggling atoms when they pound against a wall the averaged momentum transfer is felt by us as pressure my question is most knowledgeable people wright in books , we can't achieve 0K thermodynamic temperature as it's impossible to seize the motion of atoms completely. Well i have a way around it in this big intersteller space let's assume there is a place where no radiation is present yet then why zero kelvin can't be present there there we don't have to deal with seizing of atomic motion as we are no longer dealing with atoms or matter , so is it that in space 0K is possible but matter can't be manipulated to completely loose it's motion then 0K is observable thing and not a impossible scene .
>>>I can't exactly figure out what we mean by temperature>>> good question - use google
But google can't tell weather 0K can exist, if not you then there's nowhere else to approach.
@@lecturesbywalterlewin.they9259 have you been through the entire text?
I think Professor Lewin has pointed the way for on line demonstrations to be adapted to the TEACHING of Science and the humanities. The practical that are to be assessed could to be in schools or at special centres.
thermal expansion on heating basically occurs because of the due rise in temperature results in increased amplitude of oscillations between atoms of a material so the average sepration between them increases. My question is that in most textbooks rod is shown to expand only in one way, while in reality, it should expand on both ends in opposite directions?
rods expand in all directions, if the length is 1 m and if the extension is 0'.1% then the rod expands by 1 mm. If the radius is 5 mm, then it expands by 0,005 mm which is 5 microns
Sir thanks a lot for clearing my concepts...i am a hosteler and am returning back to my hostel where i cant be under your guidance....thanks a lot sir...wish a wonderful happy birthday and
God zegene je
:)
Do you have any book of yours, or any book you can prefer me to study, im in 11 th grade in India, and am preparing for NEET(hope you can google that).
Well you're my mentor.
"For the Love of Physics" by Walter Lewin and Warren Goldstein
I have read it and is really wonderful.
Lewis sir I m just loving u more more nit just as a physics but as person I owe u so much Obeisances to u alma mater….May you live long and stay Happy always …Really wish I had aptitude a chance to be there learning from u in MIT …..Next birth for sure
All the best
@@lecturesbywalterlewin.they9259
Sir where can I get all ur lectures and also I really wanted guidance to pursue astrophysics and physics I m 34 yet I wann to do it I
i m an engineer could 7 please guide me through
@@anubhaagarwal4224 Watch all my 94 MIT course lectures. Start with 8.01, then 8.02, then 8.03. Do all the homework and take all my exams. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam* You will find all information you need on this channel (notice the three playlists "Homework & Solutions").
8.01 & 8.02 will each take about 200 hours, 8.03 about 250 hours.
@@lecturesbywalterlewin.they9259 sir I m doing tht hv already begun but do u think me being 33 now if I wann I cn genuinely get thru some very good university and do wonders in physics and astrophysics
Sir in an atom electrostatic force btw e and nucleus act as centripital force, but why that happens only in atom but not in isolated proton and electron?
you should read up on some atomic physics - use google.
best way is to calculate their potential energies if the come -ve probably they are rotating
Greetings Sir,
Does your book For The Love Of Physics contain contain theory to understand the topics or is it an entertainer?
I like your way of teaching and would surely want to buy the book if it has theory to build up my concepts for various examinations. please help me out with one more thing, is there a chapter on Thermodynamics?
Regards.
You will Love my book "For the Love of Physics"
It will not help you much with your Physics exams.
Thank you so much Sir. Will love it indeed.
I really appreciate your effort to reply each and every comment on your videos! God bless!
Regards
Thank you so much professor!
Is there any substance other than water whose crystals float on its liquid form ?
+Shivam Agarwal Other substances that expand on freezing are silicon, gallium, germanium, antimony, bismuth, plutonium and also chemical compounds that form spacious crystal lattices with tetrahedral coordination.
Sir, If a body emits white colour then how to apply wein's displacement law? I mean what is the lambda max in this case?
white light contains of many different wavelength. Look up "black body radiation".
20:56 I found the answer to be 1mm. The formula that I used is R = 2d(1+α_2·∆T)/{(α_1-α_2)·∆T} and θ = l(α_1-α_2)∆T/(2d). These gives ∆h = R(1-cosθ) = 1mm. Please tell how to proceed to the correct answer.
Sir really like your lectures. sir I have a question from calorimetry. In the latent heat of water will the specific latent heat increase or decrease with the change in pressure? I have a confusion since water at low pressure boils below 100 celcius so will the latent heat always remain same?
Why we join 2 points to straight line .. is it experimentally determined that linearly expansion of metal with temp or what .?
If the material is uniform, then, the volume will change with temperature but not the shape. Thus the expansion between any 2 random points will be linear. use google
Sir, a magnifying glass converges sun rays into a narrow beam. Does it convert it to a laser ???
a laser beam is already focussed
@@lecturesbywalterlewin.they9259 so does it mean that it focusses the sunrays and give it the power of a laser beam ??
Yes
sir, I have always had a doubt that, on discussing with my physics faculty, is always dismissed.
If we take a concave hole, i.e. like a rectangle that had one side bent inward. If we make a hole of this shape on an aluminium sheet (2D), will the areal expansion cause the material to move into the hole or away from the hole? Will the convexity of the material affect the direction of expansion?
If its concavity is high, then there wont be enough area for expansion resulting in bursting. Similar to wine glass which is highly concave will burst if heated too much.
Sir at 20:25 I am getting the vaue of d to be 2mm and not 4mm. Sir I used formula thickness × angle of arc= difference in delta l. This gave angle of arc. Using this I found radius of inner circle. Then deducted radius × cosine of angle of arc from radius. Which gave 2mm. Please clarify.
you must have made a mistake
you must have made a mistake as your answer is not correct
Thank you Dr. Lewin. raphael santore
Now I'm in 11th std,
Sir I want to ask you that should I opt for IIT or should I do Bsc,Msc and Phd in physics
and a difference is for bsc in physics we don't need entrance exams as for iit is.
what should i choose ? can you advise?
I cannot advise you as I do not know you. Talk to your teachers.
@@lecturesbywalterlewin.they9259 ok sir I'll find it myself , thank you sir.
@@rajwardhangaisamudre did u find out?
respect for you!
The fact that America still uses imperial measurements is a sad bit of politics. Specifically, in the United States we officially switched to SI in 1975, but we didn't fund the transition. President Ford created a board to coordinate the transition of the United States to SI, but the board was abolished and all the progress halted by Reagan even though the law is still on the books that says we should be transitioning. The United States officially uses the metric system as "the preferred system of weights and measures for United States trade and commerce" but conversion is voluntary and no funding is in place.
yes, it's very confusing. 12 inches in a ft, 3 ft in 1 yard brrrrrrrrrrrrrr
450 grams in 1 US lb. 28 gr in 1 oz
I have a question. Assume that we have some mercury of V0 volume at temperature T. I increase T by an amount of dT. At T+dT, I have V1 = V0 + dV, where dV = V0*beta*dT (Eq. 1). Now I decrease the temperature from T+dT to T, I have V0 = V1 + dV, where dV = V1*beta*(-dT) (Eq.2). Now, I take the absolute value of dV, then I have dV = V0*beta*dT = V1*beta*dT. However, V0 is not equal to V1. I should be wrong somewhere!!!
The only way I can explain it to myself is that beta depends on the temperature.
I know its too late but if anyone else is interested (and since this is actually a good conceptual question) the assertion that change in volume when heating is equal to negative change in volume when cooling is wrong.
If you think about it it's like with railways thing that was presented here they bent on a scorching day and stayed bent on cooler days the linear expansion wasn't equal in both directions.
sir I do have a doubt that in my 11th std textbook under lesson thermal properties of matter they've given relations between Beta and Alpha in ther it is Beta = 2 Alpha
where you say Beta = 3 Alpha ( 34:19 )
sir please tell which is correct.
send me the text in your book
@@lecturesbywalterlewin.they9259 how do i send the text of textbook here in comment, do any other ways are there?
@@rajwardhangaisamudre my beta is 3 alpha
@@lecturesbywalterlewin.they9259 sir my texbook of 11th std is of maharashtra board of India,
and in there it says under the topicrelation between co-efficients of expansion, relation between beta and alpha, and it's result is-
"since the values of Alpha are very small, the term -
alpha^squared ×T^squared is very small and may be neglected.
Therefore Beta = 2Alpha "
sir for even if i write 2 alpha in exam for a situation
but i want to know in fact or according to till now proven theories on heat, what will be the real value -
2 alpha or 3 alpha
Temperature was defined such that it depended linearly on change in length of the mercury column. So that is how it was defined. We measure the change in length of mercury as it goes from 0°-100°C and divide it into 100 equal lengths, each corresponding to a particular temparature. So why is it that for all materials, one degree change in temperature corresponds to same change in length (for a material of given length)?
I know it seems obvious, but I can't come up with the logic myself. I'm getting stuck here.
>>>>>So why is it that for all materials, one degree change in temperature corresponds to same change in length (for a material of given length)?>>>
NOT TRUE
Ohhh! So some are experimentally found to be so?
look at the table of expansion coeff for various substances in
en.wikipedia.org/wiki/Thermal_expansion#Coefficient_of_thermal_expansion
Thank you :D
perfect lesson
7:00 to 7:05 loved it! In your face, Imperialism!
Why no thermodynamics??? I really would have loved a separate video.
(at 9:41) Does it mean that the length of the rod is an exponential function of temperature.
yes
Thank you very much for responding prof. But why isn't this fact covered in any of the standard physics textbooks ? even the differential equation isn't hard to solve at all for a calculus based course
During heating ,In the bimetallic coil how can one know that which metal is on the inward side or outward side? What are the different forces acting on the bimetallic coil during the heating?
metal 1 and metal 2. Metal 2 has a larger expansion coeff than metal 1. If we add heat metal 2 will get longer than metal 1 thus the bimetal will coil up with metal 1 on the inside of the coil.
Thank you! I am a great great fan of you!!!
Sir, what is the difference between absorptance and absorptive power?
use google
Sir i tried to find the answer in Google as well as in many Indian high school physics books (as I'm an Indian high school student ) but none of the above mentioned sources is providing a clear concept. sir pls help...I'm really stuck in these radiation related terminologies.
Excellent lecture Sir. 🙏🙏🙏🙏 Thanks 🙏🙏🙏🙏🙏🙏🙏🙏🙏
Sir.....how to study physics😅😅.....how we will always be interested in this subject.....
Ugh wasn't watching sir lewin enough?
Couldn't agree more Sir 😂 27:49
can electromagnetic field give direction to negatively charged ion if yes then how
Hi professor. Regarding this lecture, how about if we go down below 0 degree celsius for water at atmospheric pressure(pressure not changing). It will still expand or not? Thanks.
use google to get the density of ice and water as a fucntion of temperature.
Sir why mercury does not flow in thermometer towards gravity on tilting it?
capillary action
my answer was wrong. there is no capillary action between mercury and glass. Here is the correct answer which I found online. "A thermometer tube interior cross-section is quite small … usually about 1/8 inch or less (the curvature of the glass has a magnifying effect, making the mercury column seem bigger than it actually is). Mercury does not react or even adhere (“cling”) to glass. The mercury column holds itself together by surface tension. However, if the glass tube is wide enough that the weight of the mercury is greater than the retaining effect of the surface tension, then the mercury will flow downwards abruptly. And remember the old-style hospital thermometers: it took several very brisk shakes of the inverted thermometer to force the very thin column of mercury back down into the "
@@lecturesbywalterlewin.they9259 thank you very much, sir.
I have a question that has been kind of in the back of my mind bugging me for a long time. Say I have a circular plate of metal, and a perfect square is cut in the exact center of the plate. If the plate is heated or cooled do the sides of the inscribed square retain their perfect straightness or will they expand and contract an curve just a little bit?
square will expand/contract maintaining its geometry as well if circle retains itself too
Please😭 , if anyone knows the solution to the problem mentioned at 20:30 please reply ,am so so curious I couldn't solve it . maybe could you suggest a video with same concept
Could you solve it? Please reply if you did🙏🏻
Heat flows from a hotter body to a colder body till the time both are at same temp. right? So that means if I have fever and I'm 100 F, then when I insert a thermometer, it will show me a lesser reading? Am I getting cooled everytime I insert a thermometer to check my temp.?
The natural temp fluctuations of your body are probably 0.01C on time scales of minutes and less. Your temp change when you measure your temperature is not even measurable as it is probably less than 0.000001C which is MUCH smaller than the natural fluctuations.
i see, thanks professor! what's that near your pocket?
So like if i heat somehing up enough, could it theoretically rip? because there can me no extra material made
If you heat something enough ,state of that thing is gonna change....like if you're heating a metal.... eventually it's going to melt and become liquid, and on further heating- gas.
Fruit is to make sure your attention is on the lesson. If your paying attention you won’t see fruit.
Professor, Thank You Soo Much!!!!!
You're very welcome!
@@lecturesbywalterlewin.they9259 Sir, I had a question, I cannot find the Heat Tranfer and Conduction video on your Curriculum on UA-cam
Sir ,at 3.54 why do you say only a straight line can be drawn?a curve connecting to those points is also possible right?
listen to what I said. I did not exclude that you can also draw curved lines.
Oh !! Yes ,sorry.
sir , i have a question not related to this topic but , i am going to ask anyway
is the carnot cycle an internally reversible process or is it a totally reversible process,
it should be an internally reversible process only as some net work is actually produced or am i wrong ? i am confused.
yes it's reversible, use google
The Carnot cycle consists of the following four processes: A reversible isothermal gas expansionprocess. In this process, the ideal gas in the system absorbs qin amount heat from a heat source at a high temperature Th, expands and does work on surroundings. A reversible adiabatic gas expansion process.
thank you sir :)
I am surprised how you casually said that you overheated the mercury thermometer and made it explode. Wouldn't the exposed mercury be extremely harmful since it releases fumes?
it's like taking *one puff of cigaret smoke* in your life time, would not harm you.
@@lecturesbywalterlewin.they9259 Sir like you did in your last lecture ? :)
Can u suggest sites where i can learn thermodynamics in a more elaborated manner ?
search the web. There are thousands of excellent videos about physics in Coursera, Udacity, edX, and elsewhere.
Anything that you would recommend personally ?
no
Lectures by Walter Lewin. They will make you ♥ Physics. Ha ha ha
Sir ....why do the liquid content in the egg solidifies after heating rather then vaporising????
It's a chemical reaction that solidifies the egg. use google for details if it evaporated the egg would explode.
dank je mijnheer
does ice expand or contract on cooling from 0 degree celcius to -5 degree celcius?
Ice contracts the instant it freezes solid, and continues contracting all the way to absolute zero. The relation is not linear, and it contracts less per unit temperature the colder it gets. The highest rate of contraction happens right at 0 Celsius just after it froze. It does not become denser than water, given a pressure of 1 atmosphere.
Halo Prof Lewin, how did you calculate the 4 mm at 20:54?
I tell you in the lecture how I did that.
Thank you kindly ✍️
Hello, Sir. At minute 31:52, why is that the same?
Magic of binomial expansion
Missing lecture on laws of thermodynamics
sir i understand the concepts but i am not able to solve numericals ........... what should i do sir.............sir i am a iit jee aspirant.........pls sir need some guidance from you
more practice
sir, can u please tell that how exactly, any of the temperature scale was originally defined (or is currently defined). actually my doubt is - say for kelvin scale, setting absolute zero temp. as 0 K is fine, setting something at 273 K is fine, and now how this scale is divided? like if i wish to go to 15 K, how will i? the change in length of a material is a bad idea as one cannot say that it will expand linearly. sir, please don't ask me to ask google as i already did it.. :)
don't be lazy - use google - all your answers are there. I found them in less than 15 sec.
Sir, are we still good friends?
Sir is there any derivation for the formula delta(L) = L *deltaT *alpha
tau=dL/dt and tau = I*alpha and alpha =dw/dt
I derive all this in my 8.01 lectures
Sir sorry for pestering again. Could you tell me where the 8.01 lectures that you have mentioned can be found? (the ones in youtube are the 8.01x) And are they more detailed(I mean do they include the proofs)?
Thank you for your lecture and kind replies Sir
All my 8.01 lectures are on this channel. Topics are listed. I too have to search. But that's not my task.
Sorry for troubling you again sir is 8.01 and 8.01x the same if not 8.01 is not in here sir
My channel has my 8.01x and 8.02x lectures. The context is slightly different in only a handful of lectures from 8.01 and 8.02. Key is that the x lectures have a higher resolution than the non-x lectures which were originally on MIT's OCW.
Ummmm. . . I'm sure someone's already asked, but is there any chance you had cantaloupe for breakfast?
Sir
What is the temp at complete space where there is no stars n anything?
google Cosmic Background radiation. The temp is about 3K.
@@lecturesbywalterlewin.they9259 but how they measured that sir
@@animations3193 use google - A Nobel Prize was awarded for the discovery of the CBR
Dear Prof. Lewin,
Is entropy a conservative property or dissipative property?
question unclear - ask google
It is the dissipative property of the universe.
Entropy is only conserved in the special case of reversible processes. Entropy is a property such that the entropy of the universe, will either increase or remain the same, but never decrease. If entropy of a system decreases, the entropy must go to another system. It cannot be destroyed.
Sir how could I make my phyics strong subject?
Leuk om dit weer te zien ! 1973
sir,at last you explain the special character of water...and u gave some examples...about skating...fishes ...i didn't understand it clearly...can you please explain it to me again
how many minutes into the lecture?
sir,it's from 45:44 to 49
ok thank you sir...
Water is very special indeed. Ice at 0 C has a larger volume than water at 0 C, that's why it floats and that why we can skate. I watched and listened to what I said. I cannot add to it. Please use Google if you want to know more details.
thank you very much sir...
And Professor also looks a little like Benedict Cumberbatch which makes him a good looking teacher
Tomorrow I have mains test and I am a bit worried . I have practised physics from ur channel but don't how tomorrow will be :)
How did you do your exam and are you a dropper or 12th
12:09 looks like a foot illusion caused by heat of the marker
How much math is required if someone wants to completely understand all of his lectures?
Just up to calc II, but if you're in a rush, learn the basics of Derivatives, Differential Equations (1st and 2nd order), Integration, and Taylor Series.
What book is being followed, Sir???
9:00.. it should be just Kelvin, not degrees Kelvin
You are politically correct - but that's not the way we speak. There are 3 temp units, Celcius, Fahrenheit and Kelvin. When my wife asks me what is the temperature I would ALWAYS say 55 degrees Farenheit thus I also say that in my lectures. In writing I would say 55 F. I would write 300 K but I would say 300 degrees Kelvin.
Sup Walter. You like Formula 1?
What is difference between heat and energy??
Energy is anything measured in Joules, that is a capacity to do work. Could be thermal energy, heat, work, kinetic energy, strain energy, chemical energy, etc.
Heat is one particular form of energy, that is a thermal transfer of energy from a hot object to a cold object. The result is that one object gains internal thermal energy, and the other object looses internal thermal energy. "Internal thermal energy" refers to the molecular level kinetic energy within the objects, which could come in the form of translation, rotation, vibration, and in metals, the unorganized motion of the conducting electrons. This is why different materials have different specific heat capacities.
Heat is the way energy tranfers from a hot to a cold object, the other way energy acts on matter is by doing work
the lower limit of temperature is quite intuitive ... every atom is at rest i have 0°K... but what about the upper limit? is it limitless?
there is no upper limit, but I suggest you ask google too.
38:50 Oral - Not to be confused
Professor! Why is the aspect ratio of these videos low.?
what is aspect ratio?
@@lecturesbywalterlewin.they9259 video quality
Because its from the 90's dawg
prof. there in the video why are you hang foods on your shirt sometimes melon some fried egg _?
I love broaches - the fried egg is the most famous one
Prof Why your Pdf lectures not working?
they are working but you do not know how to access them. For people like you I have made 3 playlists: "8.01 Homework, Exams, Solutions, Notes" similar for 8.02 and 8.03
@@lecturesbywalterlewin.they9259 Thank You prof❤️
Sir can explain transmission of heat
there are several different ways to transfer heat - use google
Heat will flow every time there's a difference in temperature; (No temperature difference means no heat exchange); heat will only flow - and flow it will - from higher temperature to lower temperature. (lower to higher is not possible); heat is exchanged by 3 ways: conduction; convection; radiation.
Don't confuse temperature with heat. (it's like tension and current).
there are an immense amount of free books available on the matter.
👍👍
27:49 What a terrible scale.😅😅😅
why does he have a melon on his shirt
Why not?
Why is he wearing a melon on his chest?
That's a badge first of all and why shouldn't he?