Did all the calculations and o_i=(1-1/k)o_f checks out Edit: I found in a comment thread that what Walter wrote on the board was just a slip of the pen. THANK YOU PROFESSOR, YOUR CHANNEL IS A GREAT RESOURCE FOR STUDENTS LIKE ME
@lecturesbywalterlewin.they9259
4 ай бұрын
yes slip of the pen, - sorryi
@yuanyi827
3 жыл бұрын
Pr.Lewin,I think you slipped up at 6:16.I think the correct solution should be σ(in)=(1-1/K)*σ(fr).
@shreyansingh9366
2 жыл бұрын
Yes
@The_Green_Man_OAP
4 ай бұрын
If σ(fr)-σ(ind) =σ(fr)/K => σ(fr)(1-1/Κ)=σ(ind) σ(fr)~σ(ind)(1+1/K+1/K²+...), K>1 ≈σ(ind)(1+1/K)
@The_Green_Man_OAP
4 ай бұрын
In his 8.02x lecture on dielectrics, he had: E(net)=E(free)-E(ind) =E(free)(1-b) =E(free)/K, where b=1-1/K => E(free)·b=E(ind) From my other comment: 1/(1-1/K)≈1+1/K => E(free)≈E(ind)(1+1/K) => E(ind)≈E(free)/(1+1/K), and as 1/(1+1/K)≈1-1/K, this fits with E(ind)=b·E(free), from above.
@lecturesbywalterlewin.they9259
4 ай бұрын
yup, slip of the pen - sorry
@umasrivastava4142
4 жыл бұрын
thanks 😊
@KeithandBridget
4 ай бұрын
8 minutes 18 seconds packed with physics and not one second wasted
@lecturesbywalterlewin.they9259
4 ай бұрын
thanx for your kind words. This video was probably made in 1996 when I was every day on MIT's video helping students with their homework for that week. They were called "Help Sessions". They lasted 57 minutes. It would then automatically rewind and it would start again all over . Day and nite for a whole week. Every week a diiferent Help session. I have done that for many years. For 8.01 in the fall and for 8.02 in the spring.
@ajms786
6 жыл бұрын
Sir I have a doubt.. In a parallel plate capacitor 2 different dielectrics with dielectric constants K1 & K2 are filled across the diagonal . The area of the plate is A.The distance between the plate is 'd'. I got the capacitance of this capacitor as ({epsilonzero}A*K1*K2/{K1-K2}d) * ln (K1/K2). But when I put K1= K2= K , It shows 0/0 form..Can you please explain this..
@lecturesbywalterlewin.they9259
6 жыл бұрын
I do not solve problems for viewers. I teach Physics. I refer you to my 8.02 lectures and my 8.02 Help Sessions which are on this channel.
@ajms786
6 жыл бұрын
Thankyou sir !
@physl2787
6 жыл бұрын
sir how you write sigma free*area/k epslon from the (sigma free-sigma induce)*area/epslon at 4:0
@lecturesbywalterlewin.they9259
6 жыл бұрын
question unclear
@The_Green_Man_OAP
4 ай бұрын
4:06 Add the two E field vectors & look at "-y" (aka "↓") component: E(total)↓=E↓(fr)+E↑(ind), assuming E(net)>0. E(total)(-y^)=E(net)(-y^) + 0·x^ + 0·z^ E(net)= E(fr) - E(ind)
@The_Green_Man_OAP
4 ай бұрын
7:51 So, E here is the original E(net) and not the new E, i.e. E(net)/K ...? Alternatively: K·(old u) = (new u) ..? Am I right in saying that there is K times more energy stored in the capacitor with the dielectric than without, at the expense of a voltage drop across the plates?
@The_Green_Man_OAP
4 ай бұрын
u(free space)=½εo·E² u(dielectric)=½KεoE·E =½Kσ·V/d =½KQV/Ad =½K²QV'/Ad =½K²ε(E')² ...🤔 u(di)/K²=u(fr)/K =(1-b)²u(di)=(1-b)u(fr) =½ε·(E')² ..What's this, does it have any significance ⁉️
@studywithjosh5109
4 жыл бұрын
Question: Since o_id=b(o_free) And 1-b=1/k -b=1/k-1 b=1-1/k Doesn’t [ o_id=(1-1/k)o_free ] ??
@lecturesbywalterlewin.they9259
4 жыл бұрын
question unclear. what I have is correct
@The_Green_Man_OAP
4 ай бұрын
You were right. He said it was a pen slip‼️ 〰️🖋️🤓
@JaiPrakash-bk3uv
6 жыл бұрын
sir why Sigma induced and sigma free is not same. why they are unequal.
@lecturesbywalterlewin.they9259
6 жыл бұрын
if they were the same that would require a dielectric constant of infinity. The net E-field in the capacitor would then be zero. A good conductor used as a dielectric would do that.
@devanshgupta3473
6 жыл бұрын
Sir what will be the capacitance of an octant of a sphere if capacitance of sphere is C?
@lecturesbywalterlewin.they9259
6 жыл бұрын
question unclear - ask quora
@devanshgupta3473
6 жыл бұрын
Lectures by Walter Lewin. They will make you ♥ Physics. Sir if we divide a sphere in eight equal parts like we divide a circle in 4 quadrant then what will be the capacitance of 1 part of sphere if capacitance of whole sphere is C?
@lecturesbywalterlewin.they9259
6 жыл бұрын
bizarre question as the charge will then be on both sides and the charge density will be huge near the sharp edges. There is no analytical solution - a numerical solution may exist but will depend on size. ask quora.
@devanshgupta3473
6 жыл бұрын
Lectures by Walter Lewin. They will make you ♥ Physics. Yes sir I also think the same but this was asked in one of the entrance test.
@lecturesbywalterlewin.they9259
6 жыл бұрын
>>>this was asked in one of the entrance test.>>> *insane question!*
@deepanshumahour3318
6 жыл бұрын
That relationship between sigma free and induce is wrong...it would be ok if we swap the position of sigma free and sigma induced
@deepanshumahour3318
6 жыл бұрын
There was just a common math mistak you did ,sir!
@lecturesbywalterlewin.they9259
6 жыл бұрын
how many minutes into the lecture?
@deepanshumahour3318
6 жыл бұрын
8.3 minutes
@lecturesbywalterlewin.they9259
6 жыл бұрын
*ha ha ha the video ends at **8:18* good luck!
@deepanshumahour3318
6 жыл бұрын
Ha ha ha that's why I said 8.3 minutes!...if you noticed sir...but just why are you diverting my concern.
Пікірлер: 56