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 Question: Isn\'t the theory of relativity concerned with the unification of physics? I mean does\'t it make its contribution to unified theory? By: Kai     Date: 2013-07-20 Answer: I am not sure what you mean by unification in Physics. If you mean unification in terms of unified theory of fundamental forces, I do not see any direct link with whatever we have covered in Special theory of relativity and that. But if by unification you mean the expectation that if no special inertial frame exists in mechanics, the same should be also be true in electromagnetic theory, then yes. By: Prof. Shiva Prasad     Date: 2013-08-03

 Question: why should lorentz transformation be linear?please explain sir. By: gautam padmanabhan     Date: 2013-07-28 Answer: This aspect has been explained in detail in Lecture 4. If we would allow non-linear terms, then following situation may arise. The same length of rod placed at different location (say along x-axis) in a frame S, may appear to be of different length in S'. This is not expected. By: Prof. Shiva Prasad     Date: 2013-08-03

 Question: Sir, will we solve the pproblem in Lorentz equation in next lectures. I have been asking which object that velocity v in this equation relative with from my high school day until now :) Thank you. By: Sa-Huynh Lam-Van     Date: 2013-08-08 Answer: The question of Lorentz Force in relativity has been discussed in some of last lectures of this course. The question that you have been asking since your high school is very genuine regarding the velocity v in the expression of Lorentz Force. As the electric and magnetic fields are frame dependent, the answer to your question is as follows. Choose a frame. Find out E,B and v in this frame and use the expression of Lorentz Force to find the force on the charge in that frame. By: Prof. Shiva Prasad     Date: 2013-08-08

 Question: Sir, I have been taught that an electric charge at rest will only has E field and one moving has both E and B field. If EM fields are frame dependent, is it relative like v, is it something real of only the product of mathematics? Why when moving as the same speed as e charge, we can\'t feel B field? By: Sa-Huynh Lam-Van     Date: 2013-08-09 Answer: Your question has been answered in detail in Lectures 22,23 and partly in 24. Yes electric fields and magnetic fields are frame dependent. What appears to be pure electric field in a frame could appear as a combination of electric and magnetic field in another frame. In the word of Resnick's book, these fields are as real as measurement is. If you measure field due to a moving charge in a frame you would notice both electric and magnetic fields. Another observer in a different frame may find this charge at rest and if s/he measures the field s/he will find only electric field. By: Prof. Shiva Prasad     Date: 2013-08-09

 Question: This lecture series is outstanding. Is there any chance that you may follow up with a series on General Relativity? (NPTEL seems not to have any video courses on this topic). By: Chris     Date: 2013-08-27 Answer: I am happy that you find this lecture series outstanding. Thanks for the compliment. No I am not following it up with any course on General Theory of Relativity. However, I am not sure if NPTEL has any such plan. I shall inform the co-ordinator about this. By: Prof. Shiva Prasad     Date: 2013-08-30

 Question: can magnetism be explained on the basis of theory of relativity? if so, how? By: Rishi     Date: 2013-09-26 Answer: I do not see any direct relationship. However, if we take into the fact that electron spin contributes to the magnetic moment, then one can say yes. By: Prof. Shiva Prasad     Date: 2013-12-06

 Question: can magnetism be explained on the basis of theory of relativity? if so, how? By: Rishi     Date: 2013-09-26 Answer: I do not see any direct relationship. However, if we take into the fact that electron spin contributes to the magnetic moment, then one can say yes. By: Prof. Shiva Prasad     Date: 2013-12-06

 Question: Sir,according to 1st postulate of SPTOR,speed of light in constant in all inertial frames.But when the light travels from one medium to another the speed changes according to the refractive index of the medium.But speed of light should be constant.Why? By: ANUPAM     Date: 2013-11-28 Answer: When we say that the speed of light is constant in all inertial frames, we always mean speed of light in vacuum. In medium the speed does become smaller. By: Prof. Shiva Prasad     Date: 2013-12-06

 Question: Law of conservation of mass, mass never created nor destroyed.but as per einsten mass is varying with velocity. How can i accept both statements? By: venkatesan     Date: 2013-12-01 Answer: Conservation of mass is a non-relativistic law, which in its strict terms is not valid in relativity. In relativity, there is no difference between mass and energy as the two are related through a fundamental constant. So one can also say that conservation of mass is valid if mass is taken to mean the energy also By: Prof. Shiva Prasad     Date: 2013-12-06

 Question: Sir, Consider a body moving with relativistic speed having dimension of Planck\'s length, then length of the body will be contracted or not? By: sunil kumar     Date: 2014-01-05 The co-ordinator will post his answer

 Question: sir is earth an inertial frame ? sir as it accelerating those that means that we cant apply the formulas of special relativity on earth as frame of reference ? sir ur lectures are simply grt i just saw ur 1st lecture n it ans lots of question that came to my mind when i studied it in class ty sir By: ripul arora     Date: 2014-02-14 Answer: Thanks a lot for your appreciation. I am happy that these lectures clarified a lot of doubt that you had in college. Coming to your question, yes it is true that earth is not an inertial frame. However, so long one understands this limitation and is ready to provide corrections, when needed, we can treat earth as an "approximate" inertial frame. By: Prof. Shiva Prasad     Date: 2014-02-28

 Question: sir in your 1st video you talked about maxwells equations sir is there any video lectures on your nptel website on development n derivation maxwells equations n how they predicted that they predicted that electromagnetic waves have velocity of light ? By: ripul arora     Date: 2014-02-14 Answer: Even though I have not checked, but I do think there are lectures on electromagnetic theory in NPTEL. Electromagnetic wave is a standard topic covered in most of first year level books on Electricity and Magnetism in universities. By: Prof. Shiva Prasad     Date: 2014-02-28

 Question: sir i saw a documentary on relativity on internet in it they said that before Michael Faraday experiment scientist use to think in terms of individual forces or powers but after that experiment the concept of common energy behind all these forces came sir can u plz explain this in detail ? By: ripul arora     Date: 2014-02-15 The co-ordinator will post his answer

 Question: sir i discussed the question with someone that is earth an inertial frame they said that if you are talking about the objects on earth then yes you will take it as inertial frame because both the object and earth faces same acceleration so the effect gets canceled By: ripul arora     Date: 2014-03-07 The co-ordinator will post his answer

 Question: sir if earth is not an ideal inertial frame then does that means that the forces that we measure on earth are not real or they don\'t follow newton third law of motion? sir is there any way that we can theoretically think of derivation newton 3rd n 1st law of motion from 2nd law of motion ? By: ripul arora     Date: 2014-03-07 The co-ordinator will post his answer

 Question: sir while discussing that question with someone he said that every thing on earth including are atmosphere moves with it as its a part of earth sir he also said that if we send an helicopter upward and allow it to stand it in air for sometime when it will come back it will come on same point By: ripul arora     Date: 2014-03-07 The co-ordinator will post his answer

 Question: previous question continued sir it will land on same point from where it takeoff sir why will this happen sir can you explain ... sir i wanted to thank you for these lecture because only your 1st lectures cleared my old wrong concepts thank you sir By: ripul arora     Date: 2014-03-07 The co-ordinator will post his answer
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