Hi professor, the phenomenon you referred to of 2 jet engines creating a beat is known in avionics engineering as: "resonance offset", and it is real and deliberate. If the 2 engines were perfectly in time it could create damaging resonances, which probably wouldn't be capable of bringing a plane down, but are definitely strong enough to damage components. Planes have sensors that measure for resonances and damp them automatically, while a great deal of time is spent calibrating this system on the ground. The SR-71 has extensive systems which monitor how the 2 engines are performing together and automatically cuts out power if a resonance or mismatch of power is detected, since at high speeds this could easily bring a plane down. Pilots report this mechanism causing nausea.
Hello professor,I am one of the students at UofT, your lectures are definitely a precious gift for me since though we use the textbook also written by French, there are a lot of cumbersome equations which dives me deeply into math instead of understanding clearly the physical mechanism behind it. Now I've understand all of them very clearly through watching your lectures, they make sense now.Thank you very much. Hope you have a good time!
Sir you're one of the best physics teacher in the world which I know You're one of the greatest reason why I inspired to do research in Physics. And believe me you have inspired a lot of future physicists in the world. You are an inspiration Thank you sir 🙏 Respect from IISER Bhopal, India
Hello, Professor. Gamma depends on L (inversely proportional) because L gives a sense of inertia in the RLC circuit, that drives the current even after the capacitor plates have discharged, after a quarter cycle. And gamma for any system is bound to depend inversely on its inertia, because it is more difficult to slow down an elephant than it is to slow down a human.
If you ever want to tutor when your done with large classes I'd love to meet you in person some day. I learn so much from you if I ever figure out something great I'd name you as it's Name... The Lewin Effect! (Le = The and then just add Win! The Win!) Such a cool name.
I think the reason why L also has something to do with the decay time,is the self-inductor converts energy to magnetic field energy, but circuit does not lose that energy.It can be convert back to current.If L is very large, the current won’t go very high.Then the lose of energy in terms of heat in the resistor will become slower.So it is reasonable that higher L->higher N(longer it would take to reduce the amplitude by a factor of e.)
Hello professor Lewin, I have been thinking about the question you ask @ 1:07:50. The best answer that I can come up with is that as the resistor dissipates thermal energy it changes the changing magnetic flux through the inductor creating a back current that forces more current through the resistor. or maybe a better way to say it is as thermal energy is released it dissipates the magnetic energy that becomes more available current that creates heat at the resistor.
Professor, at 33:11, shouldn't e^(j(wt+a)) = cos(wt+a) + j*sin(wt+a)? How could you leave out the sine part and only take the cosine part in the final equation? Thank you!
Hello Professor, I am truly grateful to you for providing such fine quality lectures on physics free of cost. Thank you very much.. your lectures have helped me a lot😄.. The assignment PDF is no longer available though..Could you check it up?
i want to be like you 1 day .....no !! sorry!....i will be like you 1 day.........!,,,,thanks professor for showing that teaching has no limits...thanks a lot sir.
Sir please deactivate the advertising option on your channel.. these are the best lectures in the world but please these adds are ruining your lectures..
Here I am again.. Let's say -1/4Q^2 equals h, so we obtain (1+h)^1/2 when we apply the square root on the expression that relates the omegas. Applying Taylor Expansion we get 1+1/2*h (we can omit higher degrees given that h is small). Replacing the proper value of h we find that w=w0*(1-1/(2*4Q^2)). I found the 8! ;)
There is also a beat phenomenon between the oscilloscope's horizontal frequency and the frame rate frequency of the video recording, that's why the images are so restlessly running from left to right
Greetings Professor, First Thank you for the wonderful lecture... I have two questions, what would happen if I have more than 2 oscillation like 3 oscillations at a relatively same frequency( for eg 244, 245, 246 Hz)? And How should I go about thinking this sort of question/ questions, mathematically/deductively or I should do an experiment to find out? Your advice/hints would be hugely appreciated. Second, I think 'L' in LCR corresponds to mass in SHM, at equation level they both represent inertia of a system. (This is, though I think is cheating at some level, by the way, my explanation to the question posed by you in the lecture)
Do Beats phenomena also occur when more than two SHM involves in? (Like three SHM with 244,245,246 Hz frequency respectively. would they still show Beats? ).
Kindly verify(1.08.25) Energy dissipation in inductor takes place because direction of current changes through the inductor. Magnetic flux associated changes leads to back emf. Work is done against back emf during a part of oscillation. Work done by the emf (later) does not equals work done against it. Thus There is some energy loss.
Hello, I think in your analysis of damped free osscilations, you miss out 2 specific solutions, over damped, under damped, and critically damped. Im not sure how your method missed the two solutions however one is an exponential decay, and one is an exponential decay times by a factor of t, with no osscilation
Sir I have a very simple doubt for you that I've been pondering over. I still haven't got an appropriate answer to this yet. The doubt is that , if we have a tennis racquet , and we swish them with an amount of force, we hear a malignant amount of sound. How is that ? Hear we only have amplitude with a very , very less frequency(obviously below 20 Hertz) . even if we tell that we are striking the particles in the air and thus , we are producing sound, why does not it apply to other things as well. We depend mainly on the frequency of a vibration an object for its audibilty.
+Shricharan Dravid Messi You hear a sound when you put your hand on the table. You hear a sound when you push the keys on your key board. In all cases you produce a pressure wave which is sound. No law is violated.
sir we are not able to download material from the provided link It would have been very helpful if along with these beautiful lectures we could have access to the notes and textbook references so we could pursue further. Thank you in advance.
The inductor reacts to the change in the electric field, opposing it, and thereby reduces the current thru the resistor, and therefore reduces the energy dissipation.
In this lecture you have asked one question that why L comes in the damping constant R/L , in the case of a RLC circuit.I think the possible answer is according to Lenz's law the inductor owing to its self inductance impedes the increase in current through the circuit, as a result of that it inhibits the accumulation of charge in the capacitor..Hence it is damping the response...Am I correct professor?
+Arnab Mallick I have a little problem regarding your reply..... Based on the formula, gamma = R/L, it clearly shows that as L gets larger, it is more difficult to dampen the change in current..... Thus, I think inductance is used to impedes the DAMPENING EFFECT of the resistor.
+yao shen deng I agree. As the L goes up I goes down, which creates less thermal energy over the resistor. After all when L goes up there's less current needed for the same amount of energy in the magnetic field (due to E = L * I^2 / 2). So for the same amount of energy in the circuit you'd have a smaller loss of thermal energy and therefore less damping.
explanation why gamma is proportional to 1/L: in a circuit, inductor always try not to change direction and magnitude of current. so when current introduces in the circuit , it is inductor which keeps minimize the magnitude of current and thus reduces energy loss in resistor. is my explanation right ,sir?
what you write is not an explanation. Lenz Law dictates that a self inductor will oppose a change in magnetic flux inside the self inductor. No more and no less
It's been a while since I have been watching the lectures of the Professor and I still haven´t managed to figure out the mistery of the food at his shirt 🤔
For the general solution of the differential eqn. in complex plane you took the function to be Ae^(j(pt+α)) what is the use of taking α. I did the solution without taking α and it works just fine. Was it taken to accommodate the phase difference when required?
+Ayan Gangopadhyay Without a phase angle, sigma, your solution is not as general as it can be. But for cases where sigma is zero your solution is fine.
Hi, professor, I´m from Brasil, Aracaju capital of Sergipe, and I need your help, because I love your lessons, so , is this video, where are de english legends ?
Many thanks Professor, I´m 74 years old and so my hearing is not the same. But I´ll try to hear you ! And Merry Xmas for you and your family ! @@lecturesbywalterlewin.they9259
Hi! First time showing up! Here is another one whose live has changed due to these magical lessons.. :)) Only one question: why does wave amplitude change when you set different distances between the tuning folk and the microphone? Maybe because pressure vanishes with distance? Thanks!
58.57 you said by simply replacing q(1) by minus q(max). we got it from initial conditions. please explain me what this -ve sign signify, why it comes out -ve , can it be +ve?
He meant as the angle alpha is small (5.7 degrees) although he mentioned it theta but it's fine then cos(5.7)is approximately 1 and from the equation q1= - qmax/cos(alpha) hence q1 is approx -qmax
Hey Mr. Lewin, For a simple pendulum swinging until it comes to rest: Does the air resistance it experience depend on its angular velocity? I.e. Air drag is high during the first 10 seconds and air drag is low during the last seconds. My physics teacher says instead it depends on the acceleration?
*NOT angular velocity and NOT acceleration.* It depends on the linear velocity of the bob at the end of the pendulum. Watch my 8.01 lecture on friction. I dis cuss air drag in great detail and do demos.
Respected Sir, I had one small doubt regarding the graph you made in the video for x v/s t after damping [ 36:23 ], you said that the time period is unique, but sir, the frequency is reducing [according to w^2= Wo^2 -γ^2/4]... shouldn't the time period increase ?
8.03 is the third Physics Course at MIT. 8.01 and 8.02 are Institute Requirements and have to be taken by all Freshmen, but 8.03 is only required for Physics majors.
Professor, you said that higher values of Q will result in low values for the angle alpha. Does that mean that low values of Q will result in higher values for alpha?If that is the case, since q_1 = q_max/cos alpha, wouldn't q_1 become larger than q_max? (since cos alpha will have values less than 1, 1/cos alpha will have values greater than 1) And even for Q=5 (the example that you took in the video), the value of alpha is around 5.7 degrees. cos 5.7 is less than 1 (not by much) and 1/cos 5.7 is about 1.0049. And clearly 1.0049 times q_max is greater than q_max. Does this make sense, professor?
Castor Gemini How many minutes in the lecture do I say that " higher values of Q will result in low values for the angle alpha"? It would help me to answer you
Hey Mr professor I have a doubt.. For a damped(underdamped) harmonic oscillator, resonance occurs a)When external excitation frequency is equal to undamped natural frequency. b)At an external frequency less than the undamped natural frequency.. please help ASAP
yes sir I watched.. I am just having a doubt about resonance in case of damping... Because from the graph or formula for damped frequency we can say maximum amplitude occurs before omega=omega(natural) so does it mean there is no resonance or resonance at frequency less than natural frequency?
>>>Because from the graph or formula for damped frequency we can say maximum amplitude occurs before omega=omega(natural)>>> *YES* its a matter of semantics. Res freq in general is called the freq without damping. That is NOT where the amplitude is a max.
Hello, professor Lewin. I was thinking about the gamma inverse dependence on L and I wonder whether it is so, because Self-Inductance fights against the current (according to Lenz's Law) thus making it smaller. If gamma/damping is due to heat loss and heat is R.I.I, then by making the current smaller the heat loss would also decrease. Is this even remotely correct or am I completely wrong? (Time stamp 1:07:35)
@@lecturesbywalterlewin.they9259 At 1:07:22 you say "You may want to try to find for yourself a convincing reason, why the L also comes in the damping..." so I tried to find a reason. I said I think it is because Inductors fight the currrent according to Lenz's Law and by making the overall current over some time a bit smaller, the also make the heat loss a bit smaller (since heat is R times I squared). If the damping is due to heat loss, then bigger L means more "anti-current", thus less current over some time and less heat loss/damping.
respected sir, when you right LC circuit equation it is analog to mass m oscillates in damping medium here mass is oscillating but what is oscillating in LC circuits if it is electron then how it can be moved around the conductor and oscillates as well?
hellow sir i am following u and listen your both lecture series of 8.01 and 8.02 and now studying this series sir plzz recommend me book for this course...... Is the physics of vibratiob and waves by HJ PAin is good for this
I don't know that book. I used 8.03 Vibrations and Waves by Anthony French CRC Press ISBN 9780748744473 8.03 Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8
hello Mr Lewin, At 33:11 , can you explain how You had transformed the equation " X=Ae^(-Γ/2·t)e^j(ωt+α) " from the complex plain to the real one using Euler transformation?
Hello sir...can u give me a hints to solve this problem.13 tuning fork are arranged in ascending order of frequency when any two consecutive forks are sounded together the no of beat produced per sec is 2.the frequency of last fork is twice the first.what is the frequency of 10th fork? ..
Hey Mr. Lewin, During the 18 minutes of solving that differential equation, you said you were going to do it exactly the way that 'french/france' does it? Is it french or france and where can i find his derivation?
8.03 Vibrations and Waves by Anthony French CRC Press ISBN 9780748744473 8.03 Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8
gamma = R/L it depends on 'L' like the mass 'm' effect damping in gamma = b/m lesser m will get more damped oscillation same with L in the circuit. or as L opposes increase in current (-L di/dt) rate of flow of charges are slowed down a bit and so less energy of charges will be dissipated to heat becoz of resistor . if L was not there the K.E. energy of charges would have dissipated more to heat. it feels good to me , might be right one.
some people make sense of what they're hearing better if they close their eyes to think about it for a few moments. that's not inherently disrespectful.
How to upset Professor Lewin: Negligently forget to scream stop in an attempt to make him think physics is broken. Just kidding, thanks for the lectures
He expects the solution to be an oscillation, and so he uses the function for an oscillation in the complex plane. See Euler's formula: en.wikipedia.org/wiki/Euler%27s_formula
Also.. What is the resonance condition for a free damped(underdamped) oscillator.. What is the difference between resonance and maximum amplitude or are they same?
sir for a free damped oscillator..say it is underdamped... then obviously its frequency is less than natural one..so in a free damped oscillation when will resonance occur?
Sir, regarding the role of L in gamma I spent lot of time mulling over it and eventually came to a conclusion which I feel isn't certain and I'm unable to articulate it too. So 🙏 plz tell me that answer
Sir, at 1:12:15, you have the solution for overdamped systems on the board. When I went through the process of solving, I still have an oscillatory term: z=A_1e^-[gamma/2 + (gamma^2/4 - w_0^2)^(1/2)t]*(cos(alpha) + jsin(alpha)). What am I missing here?
Lectures by Walter Lewin. They will make you ♥ Physics. I don't doubt your answer, but substituting n into p=n+js doesn't get me there because we end up with a cos term
@@vijayr1485 Your solution has no oscillatory term in it. cos(alpha) is a constant and does not depend on time. I assume Walter has combined the cos(alpha) into the A_1 constant, to get to the same solution. I am not sure why the solution is the summation of the A_1 and A_2 parts, though. I would expect the A_1 and A_2 part to be two separate solutions.
Hello, sir! Could you send me another link to the asignments of lectures 1, 2 and 3? For some reason, the link in the subscription refuses to provide me the documents. Hope I do not take much of your time, and thank you very much for the help!
I would have to rewatch a large part of this lecture which I gave in 2005. I don't have the time for that. I suggest you watch it again. Obviously what I did was correct (maybe it was negligably small)
sir i wanted to ask that the frequency of both the balls at 10:50 are different? but you have oscillated them simultaneously. what makes them go out of phase?
Lectures by Walter Lewin. They will make you ♥ Physics. oh!! sorry sir I didn't listened it carefully..😑.There is always a minor difference in there frequencies.
Sir is it because sound wave of one drop dies in amplitude when other drop produces wave. Therefore one wave amplitude does not cancel the other sound wave's amplitude.
Why did you assume that Z=A*exp(j*(pt+alpha)) .Later on you assumed that p=n+js and that smells a lot like a La Place to me,intution tells me it has to do something with La place transformation, am I right ?
+Lectures by Walter Lewin. They will make you ♥ Physics. Yes you said that p must be a complex number,and therefore p=n+js ,so you calculated p^2 and then substituted it back into your equation. Then you worked with p only which is obviously in complex domain,and at the end you got back to your solution in form of x(t) which is in time domain ,isn't that a La Place transformation? And one more question we did damping( a subject 'Linear and nonlinear electrical circuits' and besides definition that Q=omega(zero) / gama ,he introduced that Q=2*pi*[(Energy summa at time t ) / delta of Energy summa at time t+T)] {just reading it from my notebook so I really couldn't write it the other more understandable way} and he also gave an example of a ball falling from some height h ,first it has the highest height h after 1 period it has height h1 so going back into his equation he got Q=2*pi* ((m*g*h)/m*g*(h-h1))=2*pi*((h)/(h-h1)) but what does this equation really shows me? I didnt have time to ask him because the lecture ended with that equation.
@@lecturesbywalterlewin.they9259 Thanks you sir for replying..but sir...I want to ask you that hard problem solving is one approach? ... please sir guide me..
Hi professor, the phenomenon you referred to of 2 jet engines creating a beat is known in avionics engineering as: "resonance offset", and it is real and deliberate. If the 2 engines were perfectly in time it could create damaging resonances, which probably wouldn't be capable of bringing a plane down, but are definitely strong enough to damage components.
Planes have sensors that measure for resonances and damp them automatically, while a great deal of time is spent calibrating this system on the ground.
The SR-71 has extensive systems which monitor how the 2 engines are performing together and automatically cuts out power if a resonance or mismatch of power is detected, since at high speeds this could easily bring a plane down. Pilots report this mechanism causing nausea.
very interesting - thank u
sir lewin you are a really a great mentor for me as your lectures are really helpful for students like me living in India.
Karanveer Singh
Brilliant. Brilliant. Professor Walter you are a light in my life ! I wish I could be your close friend!
:)
Absolutely right
Hello professor,I am one of the students at UofT, your lectures are definitely a precious gift for me since though we use the textbook also written by French, there are a lot of cumbersome equations which dives me deeply into math instead of understanding clearly the physical mechanism behind it. Now I've understand all of them very clearly through watching your lectures, they make sense now.Thank you very much. Hope you have a good time!
Wonderful!
Sir you're one of the best physics teacher in the world which I know
You're one of the greatest reason why I inspired to do research in Physics.
And believe me you have inspired a lot of future physicists in the world.
You are an inspiration
Thank you sir 🙏
Respect from IISER Bhopal, India
Wow, thanks
Respected sir, thank you very much for clearing my concept regarding beats and damped free oscillations.I am really great full to you.
You are very welcome
Respected sir u are great
I am from Pakistan
Hello, Professor. Gamma depends on L (inversely proportional) because L gives a sense of inertia in the RLC circuit, that drives the current even after the capacitor plates have discharged, after a quarter cycle. And gamma for any system is bound to depend inversely on its inertia, because it is more difficult to slow down an elephant than it is to slow down a human.
The best lecture on damped oscillation .Thank you🙂
You are welcome
BEST LECTURE EVER I HAVE CONFUSION FROM SCHOOL TIMES
you are just great i understood all the concepts and i am able to solve the questions by myself..
great
There cannot be a better lecture on damped oscillations.
Dear Levin, greetings from Istanbul. We love you :)
Super!
My genius sir...thank u very much for ur beautiful lecture😍😍hope that one day I shall meet with you😍
this beat phenomenon is best demonstrated in music by playing Tremolo Harmonica. Even in accordian we may observe it.
Damping: 13:00
If you ever want to tutor when your done with large classes I'd love to meet you in person some day. I learn so much from you if I ever figure out something great I'd name you as it's Name... The Lewin Effect! (Le = The and then just add Win! The Win!) Such a cool name.
2:50 how ??????
That dotted line
Its incredible
I think the reason why L also has something to do with the decay time,is the self-inductor converts energy to magnetic field energy, but circuit does not lose that energy.It can be convert back to current.If L is very large, the current won’t go very high.Then the lose of energy in terms of heat in the resistor will become slower.So it is reasonable that higher L->higher N(longer it would take to reduce the amplitude by a factor of e.)
Hello professor Lewin, I have been thinking about the question you ask @ 1:07:50. The best answer that I can come up with is that as the resistor dissipates thermal energy it changes the changing magnetic flux through the inductor creating a back current that forces more current through the resistor. or maybe a better way to say it is as thermal energy is released it dissipates the magnetic energy that becomes more available current that creates heat at the resistor.
a resistor dissipates energy (heat) *I^2R Joules/sec. A conductor does not dissipate energy.
Professor, at 33:11, shouldn't e^(j(wt+a)) = cos(wt+a) + j*sin(wt+a)? How could you leave out the sine part and only take the cosine part in the final equation? Thank you!
Only the real part of the solution matters.
Hello Professor,
I am truly grateful to you for providing such fine quality lectures on physics free of cost. Thank you very much.. your lectures have helped me a lot😄..
The assignment PDF is no longer available though..Could you check it up?
they are available but you have to know how to get them - try my playlist "8.03 Homework, Exams, Solutions, Notes"
It's Done..Thank you for your response!
You really make us love physics
i want to be like you 1 day .....no !! sorry!....i will be like you 1 day.........!,,,,thanks professor for showing that teaching has no limits...thanks a lot sir.
Sir please deactivate the advertising option on your channel.. these are the best lectures in the world but please these adds are ruining your lectures..
there is suppose to be ONLY 1 ad at the start of each lecture. Have contacted the ZOOM people to make sure that there is ONLY 1
I mean, these advertisements on lectures on RUclips are a means of income to Professor Lewin. How would you expect him to switch them off?
Hello sir, can I use these lecture for my JEE advanced preparation?
Here I am again.. Let's say -1/4Q^2 equals h, so we obtain (1+h)^1/2 when we apply the square root on the expression that relates the omegas. Applying Taylor Expansion we get 1+1/2*h (we can omit higher degrees given that h is small). Replacing the proper value of h we find that w=w0*(1-1/(2*4Q^2)). I found the 8! ;)
There is also a beat phenomenon between the oscilloscope's horizontal frequency and the frame rate frequency of the video recording, that's why the images are so restlessly running from left to right
Greetings Professor, First Thank you for the wonderful lecture... I have two questions, what would happen if I have more than 2 oscillation like 3 oscillations at a relatively same frequency( for eg 244, 245, 246 Hz)? And How should I go about thinking this sort of question/ questions, mathematically/deductively or I should do an experiment to find out? Your advice/hints would be hugely appreciated. Second, I think 'L' in LCR corresponds to mass in SHM, at equation level they both represent inertia of a system. (This is, though I think is cheating at some level, by the way, my explanation to the question posed by you in the lecture)
question unclear
Do Beats phenomena also occur when more than two SHM involves in? (Like three SHM with 244,245,246 Hz frequency respectively. would they still show Beats? ).
yes
Sir you are great ❤
Kindly verify(1.08.25)
Energy dissipation in inductor takes place because direction of current changes through the inductor. Magnetic flux associated changes leads to back emf. Work is done against back emf during a part of oscillation. Work done by the emf (later) does not equals work done against it. Thus There is some energy loss.
Hello, I think in your analysis of damped free osscilations, you miss out 2 specific solutions, over damped, under damped, and critically damped. Im not sure how your method missed the two solutions however one is an exponential decay, and one is an exponential decay times by a factor of t, with no osscilation
You assume omega^2 is a positive quantity and hence your solutions, for critical and over damped this is not the case
overdamped and underdamped *ocourse* are covered in my lectures.
you are so hillarious and a great inspiration ! :)
Oh thank you!
Excellent lecture Sir. Thanks and Regards 🙏🙏🙏🙏🙏🙏
Most welcome
Sir I have a very simple doubt for you that I've been pondering over. I still haven't got an appropriate answer to this yet. The doubt is that , if we have a tennis racquet , and we swish them with an amount of force, we hear a malignant amount of sound. How is that ? Hear we only have amplitude with a very , very less frequency(obviously below 20 Hertz) . even if we tell that we are striking the particles in the air and thus , we are producing sound, why does not it apply to other things as well. We depend mainly on the frequency of a vibration an object for its audibilty.
+Shricharan Dravid Messi You hear a sound when you put your hand on the table. You hear a sound when you push the keys on your key board. In all cases you produce a pressure wave which is sound. No law is violated.
sir we are not able to download material from the provided link It would have been very helpful if along with these beautiful lectures we could have access to the notes and textbook references so we could pursue further. Thank you in advance.
ruclips.net/video/TQR6VkYzAeY/видео.html
Amazing explanation👏👏...but I am quite shocked seeing that students of MIT are not even able to figure out such obvious mistakes🤔
No were allowed to disturb him in lecture time
How do we calculate to the time THE SWINGING SIMPLE PENDULUM STOPS? (IN AIR WITH AN ANGLE of 20 degrees startting point IN AIR)
The inductor reacts to the change in the electric field, opposing it, and thereby reduces the current thru the resistor, and therefore reduces the energy dissipation.
In this lecture you have asked one question that why L comes in the damping constant R/L , in the case of a RLC circuit.I think the possible answer is according to Lenz's law the inductor owing to its self inductance impedes the increase in current through the circuit, as a result of that it inhibits the accumulation of charge in the capacitor..Hence it is damping the response...Am I correct professor?
Arnab Mallick That sounds right !
\\/\///////@lter
+Arnab Mallick I have a little problem regarding your reply..... Based on the formula, gamma = R/L, it clearly shows that as L gets larger, it is more difficult to dampen the change in current..... Thus, I think inductance is used to impedes the DAMPENING EFFECT of the resistor.
+yao shen deng
I agree. As the L goes up I goes down, which creates less thermal energy over the resistor. After all when L goes up there's less current needed for the same amount of energy in the magnetic field (due to E = L * I^2 / 2). So for the same amount of energy in the circuit you'd have a smaller loss of thermal energy and therefore less damping.
explanation why gamma is proportional to 1/L:
in a circuit, inductor always try not to change direction and magnitude of current. so when current introduces in the circuit , it is inductor which keeps minimize the magnitude of current and thus reduces energy loss in resistor.
is my explanation right ,sir?
what you write is not an explanation. Lenz Law dictates that a self inductor will oppose a change in magnetic flux inside the self inductor. No more and no less
It's been a while since I have been watching the lectures of the Professor and I still haven´t managed to figure out the mistery of the food at his shirt 🤔
really awesome lecture now i am loving physics more then ever😍🤩🤩
Professor, is there any way we can get these mini quizes??
I donut have any doubt in physics now after this lecture.
For the general solution of the differential eqn. in complex plane you took the function to be Ae^(j(pt+α)) what is the use of taking α. I did the solution without taking α and it works just fine. Was it taken to accommodate the phase difference when required?
+Ayan Gangopadhyay Without a phase angle, sigma, your solution is not as general as it can be. But for cases where sigma is zero your solution is fine.
Gamma depends on L as well because of the Back-Emf provided by the inductor(during charging)? *asking*
Hi, professor, I´m from Brasil, Aracaju capital of Sergipe, and I need your help, because I love your lessons, so , is this video, where are de english legends ?
my 8.03 lectures have no closed captions -
Many thanks Professor, I´m 74 years old and so my hearing is not the same. But I´ll try to hear you ! And Merry Xmas for you and your family !
@@lecturesbywalterlewin.they9259
Hi! First time showing up!
Here is another one whose live has changed due to these magical lessons.. :))
Only one question: why does wave amplitude change when you set different distances between the tuning folk and the microphone? Maybe because pressure vanishes with distance? Thanks!
:)
Sir, at 1:12:10 how did the A2 term come? I understood the A1 term but not the A2 term.
It's derivation of acos(theta)+ bsin(theta)....a nd b are components along x nd y axis
Man you are god
Sir at 1:09:15 won't n be both plus and minus? Because with only plus part the solution will have only one decaying term and not both.
Great
Can you stop light with a counter wave?
1:05:45 So do you need capacitors with voltage limit of 2V_0 so that you don't break them?
(59.04) , q = q(1) * cos(wt+@)+ VC , then we got q(1) = - q(max) . what q(1) being -ve signify, why it comes out -ve , can it be +ve?
I looked at 59:04 I see no -ve
58.57 you said by simply replacing q(1) by minus q(max). we got it from initial conditions. please explain me what this -ve sign signify, why it comes out -ve , can it be +ve?
I looked at 59:04 I see no -ve
He meant as the angle alpha is small (5.7 degrees) although he mentioned it theta but it's fine then cos(5.7)is approximately 1 and from the equation q1= - qmax/cos(alpha) hence q1 is approx -qmax
There is a Q factor for L and C..related to resonance Offcourse, gives an idea about the Quality of oscillation ability.
Hey Mr. Lewin,
For a simple pendulum swinging until it comes to rest:
Does the air resistance it experience depend on its angular velocity?
I.e. Air drag is high during the first 10 seconds and air drag is low during the last seconds.
My physics teacher says instead it depends on the acceleration?
*NOT angular velocity and NOT acceleration.*
It depends on the linear velocity of the bob at the end of the pendulum. Watch my 8.01 lecture on friction. I dis cuss air drag in great detail and do demos.
Respected Sir, I had one small doubt regarding the graph you made in the video for x v/s t after damping [ 36:23 ], you said that the time period is unique, but sir, the frequency is reducing [according to w^2= Wo^2 -γ^2/4]... shouldn't the time period increase ?
yeh angular frequency waala omega hai chutiye🤣
Ask yourself: what is γ? Does it change with time?
Hi, Professor. I assume 18.03 dealt with ODE. Is this subject part of the physics degree at the MIT, compulsory or optional?
8.03 is the third Physics Course at MIT. 8.01 and 8.02 are Institute Requirements and have to be taken by all Freshmen, but 8.03 is only required for Physics majors.
Professor, you said that higher values of Q will result in low values for the angle alpha. Does that mean that low values of Q will result in higher values for alpha?If that is the case, since q_1 = q_max/cos alpha, wouldn't q_1 become larger than q_max? (since cos alpha will have values less than 1, 1/cos alpha will have values greater than 1) And even for Q=5 (the example that you took in the video), the value of alpha is around 5.7 degrees. cos 5.7 is less than 1 (not by much) and 1/cos 5.7 is about 1.0049. And clearly 1.0049 times q_max is greater than q_max. Does this make sense, professor?
Castor Gemini How many minutes in the lecture do I say that " higher values of Q will result in low values for the angle alpha"? It would help me to answer you
Professor, please explain why the two pendulums(11:47) go out of phase even after having the same length, same amplitude and same frequency?
The don't have the exact same length, there is a tiny difference between them. He says so in the video.
Thanks so much, my waves lectures are bad so these are a saviour. Keep it up.
Who do you think you're studying from😕
Even in the online class I can feel the smoke in under damped case.😂😂
Hey Mr professor
I have a doubt..
For a damped(underdamped) harmonic oscillator,
resonance occurs
a)When external excitation frequency is equal to undamped natural frequency.
b)At an external frequency less than the undamped natural frequency..
please help ASAP
I cover free oscillations with damping and forced oscillations with damping. Watch my lectures.
yes sir I watched..
I am just having a doubt about resonance in case of damping...
Because from the graph or formula for damped frequency we can say maximum amplitude occurs before omega=omega(natural)
so does it mean there is no resonance or resonance at frequency less than natural frequency?
>>>Because from the graph or formula for damped frequency we can say maximum amplitude occurs before omega=omega(natural)>>>
*YES* its a matter of semantics. Res freq in general is called the freq without damping. That is NOT where the amplitude is a max.
So resonance always occur for any case whether free or forced..at omega =omega(natural)?
its a matter of semantics. use google. Underdamped oscill have no resonance.
physics.bu.edu/~duffy/py105/Resonance.html
sir if i give you a creative question based on wave and sound,will you able to solve that question?plz sir i need help
I do not solve problems for viewers. I teach Physics. Watch my 8.03 lectures - they may be a great help for you. If not, use google or Quora
Hello, professor Lewin. I was thinking about the gamma inverse dependence on L and I wonder whether it is so, because Self-Inductance fights against the current (according to Lenz's Law) thus making it smaller. If gamma/damping is due to heat loss and heat is R.I.I, then by making the current smaller the heat loss would also decrease. Is this even remotely correct or am I completely wrong? (Time stamp 1:07:35)
how many minutes into the lecture?
@@lecturesbywalterlewin.they9259 the time stamp of the video is 1:07:35
I watched near the time you mention but I do not understand the question
@@lecturesbywalterlewin.they9259 At 1:07:22 you say "You may want to try to find for yourself a convincing reason, why the L also comes in the damping..." so I tried to find a reason. I said I think it is because Inductors fight the currrent according to Lenz's Law and by making the overall current over some time a bit smaller, the also make the heat loss a bit smaller (since heat is R times I squared). If the damping is due to heat loss, then bigger L means more "anti-current", thus less current over some time and less heat loss/damping.
@@lukastrecha6424 I would have to watch a large part of this lectuere again which is not worth my time. I am sorry.
Hi, Professor Lewin! Just one question.. Maybe it is very simple, but I am not able to get it.. Min 37:34: how 1/8 arises? Sorry if it is trivial! :(
try harder - simple math
So there is no mistake.. I have to go from 1/4 of 1/100 to 1/8 of 1/100, and squares are involved. Correct? I will keep trying!!
respected sir, when you right LC circuit equation it is analog to mass m oscillates in damping medium here mass is oscillating but what is oscillating in LC circuits if it is electron then how it can be moved around the conductor and oscillates as well?
current is oscilating
hellow sir i am following u and listen your both lecture series of 8.01 and 8.02 and now studying this series sir plzz recommend me book for this course...... Is the physics of vibratiob and waves by HJ PAin is good for this
I don't know that book.
I used 8.03
Vibrations and Waves by
Anthony French
CRC Press
ISBN 9780748744473
8.03
Electromagnetic Vibrations, Waves and Radiation
by Bekefi and Barrett.
The MIT Press
ISBN 0-262-52047-8
okay Sir....
thanks you soo much....
hello Mr Lewin,
At 33:11 , can you explain how You had transformed the equation " X=Ae^(-Γ/2·t)e^j(ωt+α) " from the complex plain to the real one using Euler transformation?
this is standard math. Use google
Lectures by Walter Lewin. They will make you ♥ Physics. You transformed the e^j(ωt+α) using Euler's and you kept only the real part ??
I hope so
Hello sir...can u give me a hints to solve this problem.13 tuning fork are arranged in ascending order of frequency when any two consecutive forks are sounded together the no of beat produced per sec is 2.the frequency of last fork is twice the first.what is the frequency of 10th fork? ..
watch my 8.01 and 8.03 lectures on beat frequencies.
10th one has frequency 42 Hz
Hey Mr. Lewin,
During the 18 minutes of solving that differential equation, you said you were going to do it exactly the way that 'french/france' does it?
Is it french or france and where can i find his derivation?
8.03
Vibrations and Waves by
Anthony French
CRC Press
ISBN 9780748744473
Hello Professor Lewin,
Do you know which two books are used for 8.03?
I know of the one book French. But what is the title of the other book you reference by Bekefi & Barrett
8.03
Vibrations and Waves by
Anthony French
CRC Press
ISBN 9780748744473
8.03
Electromagnetic Vibrations, Waves and Radiation
by Bekefi and Barrett.
The MIT Press
ISBN 0-262-52047-8
@@lecturesbywalterlewin.they9259 Thank you I will be studying 8.03 now that I have finished 8.01 and 8.02 😊
gamma = R/L it depends on 'L' like the mass 'm' effect damping in gamma = b/m lesser m will get more damped oscillation same with L in the circuit. or as L opposes increase in current (-L di/dt) rate of flow of charges are slowed down a bit and so less energy of charges will be dissipated to heat becoz of resistor . if L was not there the K.E. energy of charges would have dissipated more to heat. it feels good to me , might be right one.
prof. please tell is it right or not.
what are you referring to? How many minutes into my lecture?
at 01.07.28 you asked why "L" also comes in damping in RLC circuit.
the answer is that wL has the dimension of ohms.
Its a very Heavy Lecture
But enough for JEE
36:29, real respect for the lecture by the black shirt dude.
some people make sense of what they're hearing better if they close their eyes to think about it for a few moments. that's not inherently disrespectful.
Sir gamma inversely proportional to L is because L is providing magnetic inertia in system is this is right sir
At 26:50 isn't n=0 also a solution to the equation, with s = (𝛾 ± √ (𝛾^2 - 4 𝜔0^2)) / 2 ? Why can we ignore that solution?
for n=0 ω=0. There is no oscillation & it requires that then k=(b^2)/4m yet, we can choose b and m as we please. So n=0 is not a solution.
How to upset Professor Lewin: Negligently forget to scream stop in an attempt to make him think physics is broken. Just kidding, thanks for the lectures
if the self inductor was not made of self inducting wire will the electric field be 0?
E field is only zero if the inductor is made of superconductive material.
How to differentiate between real and imaginary of P and n (angular velocity=frequency). Is the n also a complex value
how many minutes into the video?
Thank you kindly ✍️
You are very welcome
Hi, Can anyone tell me how he get Z = Aej(pt+alpha) at 21.48 min in the video. Appreciate for the help! I am really bad at calcalus
He expects the solution to be an oscillation, and so he uses the function for an oscillation in the complex plane. See Euler's formula: en.wikipedia.org/wiki/Euler%27s_formula
Hello sir. Is the resultant beat wave produced dependent on thei phase difference between the individual waves?
watch my 8.01 lectures in which I discuss beats and beat frequency
Also..
What is the resonance condition for a free damped(underdamped) oscillator..
What is the difference between resonance and maximum amplitude or are they same?
watch my lectures or ask google
sir for a free damped oscillator..say it is underdamped...
then obviously its frequency is less than natural one..so in a free damped oscillation when will resonance occur?
@@shaileshxjain See the next lecture: ruclips.net/video/Y_DmzZcQR7A/видео.html
Sir, regarding the role of L in gamma I spent lot of time mulling over it and eventually came to a conclusion which I feel isn't certain and I'm unable to articulate it too. So 🙏 plz tell me that answer
question unclear - how many minutes into the video?
@@lecturesbywalterlewin.they9259 1:07:40
Sir, at 1:12:15, you have the solution for overdamped systems on the board. When I went through the process of solving, I still have an oscillatory term: z=A_1e^-[gamma/2 + (gamma^2/4 - w_0^2)^(1/2)t]*(cos(alpha) + jsin(alpha)). What am I missing here?
my solution is correct. This is a classic problem covered in all College Physics Books. I suggest you use Google for more information if needed.
Lectures by Walter Lewin. They will make you ♥ Physics. I don't doubt your answer, but substituting n into p=n+js doesn't get me there because we end up with a cos term
@@vijayr1485 Your solution has no oscillatory term in it. cos(alpha) is a constant and does not depend on time. I assume Walter has combined the cos(alpha) into the A_1 constant, to get to the same solution.
I am not sure why the solution is the summation of the A_1 and A_2 parts, though. I would expect the A_1 and A_2 part to be two separate solutions.
Hello, sir!
Could you send me another link to the asignments of lectures 1, 2 and 3? For some reason, the link in the subscription refuses to provide me the documents. Hope I do not take much of your time, and thank you very much for the help!
use Playlist "8.03 Homework, Solutions, Exams, Notes"
Silly question, but is that a bagel on your shirt?
So, what happened to the term exp(jalpha) at 1:12:01? Why did you omit it?
I would have to rewatch a large part of this lecture which I gave in 2005. I don't have the time for that. I suggest you watch it again. Obviously what I did was correct (maybe it was negligably small)
Nothing like old school professors
Some problem with the captions
sir i wanted to ask that the frequency of both the balls at 10:50 are different? but you have oscillated them simultaneously. what makes them go out of phase?
question unclear
watch it again. I explain very clearly why they go out of phase no matter of how hard we tried to make the frequencies the same.
Lectures by Walter Lewin. They will make you ♥ Physics. oh!! sorry sir I didn't listened it carefully..😑.There is always a minor difference in there frequencies.
Respected sir i am not able to download the assignment . Pls check tha link
watch my new playlist: 8.03 Homework & Solutions
How can we bring the complex plane eqn into the real plane as a cosine function? Somebody please help!!
use google
Sir at 10:20 you told during droplets dropping the sound never cancelled each other. Why?
THINKKKKKK
Sir is it because sound wave of one drop dies in amplitude when other drop produces wave. Therefore one wave amplitude does not cancel the other sound wave's amplitude.
Sir how at 33:16you take cos function whereas the solution of of the differential equations was in in exponential functions
google "Euler's equation"
6:09 can't believe no one's sampled that yet.
Why did you assume that Z=A*exp(j*(pt+alpha)) .Later on you assumed that p=n+js and that smells a lot like a La Place to me,intution tells me it has to do something with La place transformation, am I right ?
+Ivan Antunović How many minutes into the lecture/
+Lectures by Walter Lewin. They will make you ♥ Physics.
Forgot about it ,sorry 21:32
+Ivan Antunović when do I introduce p=n+js?
+Lectures by Walter Lewin. They will make you ♥ Physics.
Yes you said that p must be a complex number,and therefore p=n+js ,so you calculated p^2 and then substituted it back into your equation.
Then you worked with p only which is obviously in complex domain,and at the end you got back to your solution in form of x(t) which is in time domain ,isn't that a La Place transformation?
And one more question we did damping( a subject 'Linear and nonlinear electrical circuits' and besides definition that Q=omega(zero) / gama ,he introduced that Q=2*pi*[(Energy summa at time t ) / delta of Energy summa at time t+T)] {just reading it from my notebook so I really couldn't write it the other more understandable way}
and he also gave an example of a ball falling from some height h ,first it has the highest height h after 1 period it has height h1
so going back into his equation he got Q=2*pi* ((m*g*h)/m*g*(h-h1))=2*pi*((h)/(h-h1)) but what does this equation really shows me? I didnt have time to ask him because the lecture ended with that equation.
+Ivan Antunović I watched it. I give the reasons why p has to be complex. I cannot add anything to that. I cannot be more clear.
Sir .. please share best approach to learn physics very well like you..
I ate yogurt every day but *never on Fridays.* That worked also well for Einstein
@@lecturesbywalterlewin.they9259 Thanks you sir for replying..but sir...I want to ask you that hard problem solving is one approach? ... please sir guide me..