Class 11 Physics | Surface Tension | #7 Solved Example-3 on Surface Tension | For JEE & NEET

[@riteshuppal1357]

At 2:10 why did you not write... 4/3πr^3= 2× 4πr^2×t?

[@shubhammittal4993]

because volume is areaXthickness when thickness of bubble is small. otherwise integration is used when thickness not small

[@whothisguytrinabh]

Film ka hai na

[@harshitgupta8428]

very good question. cleared the concept thankyou sir

[@medishettykumar680]

Sir in previous videos anywhere did u explain aboutSoap Bubble??

[@physicsgalaxyworld]

+Medishetty Kumar What explanation you need... the soln is simple on calculation of change in surface energy which is the product of ST and area... which causes rise in temperature...

[@vishnu877]

@@physicsgalaxyworld soap bubble sir if 2 surface is in contact in air than we will multiple with 2

[@codeguy21]

Everything ok sir but still can't understand why soap bubble have 2 surface areas & liquid drop have 1 surface area.😩

[@physicsgalaxyworld]

soap bubble has inside air so one surface inside of the bubble wall and 1 outside whereas in liquid drop inside liquid is filled so no inside surface of outer wall exist... only outer surface is there...

[@p.p.3589]

@@physicsgalaxyworld gr8 explanation sir I m also confused on it 🙏🙏

[@Boomboo-f2q]

​@@physicsgalaxyworld😊

[@kreysanths3580]

​@@physicsgalaxyworldgreat sir

[@kreysanths3580]

Good question and mine too

[@rajeshtiwari4252]

Temperature changes affects Surface tension Why this isn't considered?

[@naturelover4148]

Because its negligible here.

[@kumarsantosh7376]

At 3:20 why del A is Ai - Af . It should be Af - Ai

[@satvik_srivastav]

Same doubt ...also if final area is decreased the surface energy should be released and final temp should drop...if someone know plz clarify it

[@missioniitb511]

@@satvik_srivastav See, we know some energy is stored in whole surface of liquid which we term as surface energy. So as surface area decreases, surface energy decreases and the amount of energy reduced is absorbed by the solution in form of heat and hence temp of solution increases

[@SudharsanG-s7i]

how is the surface tension T when area has changed to Af. I mean shouldn't tension change as area has changed..?

[@mohaksharma7658]

Respected Sir, There is a question regarding Surface Energy which I have done using two methods out of which one is not giving me correct result.. The Q- A spherical drop isothermally evaporates by decrease in surface energy. S tension of liquid is T, density--> rho, latent ht of vap. ---> L. What should be min. Radius of drop for this to be possible? Method 1- T* (4pi R^2)= mL --> gives me wrong ans. Method 2- assuming an elemental shell and then using T* elemental area= L* dm --->Gives me correct ans. Sir, Please tell me why method 1 is not correct..

[@physicsgalaxyworld]

+Mohak Sharma As the drop evaporates it starts from the outer surface so outer surface energy is used in evaporation of molecules on the surface and then its radius decreases and next inner layer molecules evaporate due to the surface energy of this layer and so on.... so in method 1 you are using total outer surface energy for evaporation of all the molecules upto center from outer surface thats why this is wrong... and in method 2 you are using whay I have written thats why theoretically method 2 is correct... practically question is wrong as isothermally a drop can never evaporate completely...

[@mohaksharma7658]

Understood it Sir.. Thank u very much.. :-)

[@priyanshu5017]

How you have written its initial area , from where 4 came in that please reply

[@_ranjan_18]

Sir, at 3.38 for writing the mass of the liquid, can i use 4.pi.R^2.t ?

[@krishnamurthychilaka4147]

yes

[@varadjadhav7531]

No, as given in question we have to calculate rise in temperature of liquid drop only, sorry for replying late 😔

[@vishwajeetchoudhary8264]

​@@varadjadhav7531why you saying sorry, you weren't in this field at that time ... Btw sorry for late reply

[@studyindiaguru6873]

Sorry for late reply

[@vaibhavchandra939]

Respected sir , why the final area of the drop formed is not 2 times as in the initial area ?

[@himanshuverma8648]

sir in the question you have used the radius of liquid drop but density of soap solution why sir?

[@deepakchandravanshi6274]

Sir why drop do not have two surface area?

[@tejeshrocks2667]

As thickness of the liquid drop is only about 15 to 30 molecular diameters.hence it contains only one surface

[@aanchalsharma1298]

Sir why didn't u take final area -initial area?

[@knowledgia_]

Because Initial area is of bubble, and final area is of drop(which will form & absolutely area of drop is less compare to bubble because drop is formed by bubble)

[@mehakrani5527]

why the small bubble have only one surface i didnt get it??????????

[@NoToRiOuus2001]

smaller one is a drop

[@ravinderghanghas5790]

Smaller one is liquid drop not a bubble

[@kartikrana1641]

A Drop is A Solid Sphere of Radius r and A Bubble is A Hollow Sphere With Radius R and Thickness t Where T is Very Small So We Can Consider The Radius of Inner and Outer Of Bubble to be Same So There are Two Surfaces Now

[@ayushsinha1298]

Thank you sir

[@SLASH.27]

thank you

[@indusaini1523]

Sir whole energy temp raise krne me kaam aegi kya??

[@swayamprakashkar9664]

Energy is always conserved ,only concept being used here is distribution of energy between different surfaces which is more in case of a bubble and less in liquid drop...but the total energy remains conserved as during formation of liquid drop energy gets absorbed

[@competetion]

phy galaxy is not for beginers 💀

[@__shivam]

sir, will force/length remain constant throughout the process as surface tension is given constant in this question?

[@akhakhi1386]

Who knows

[@aaryajayaprkashbhat9660]

Probably cause it depends on nature of substance , and the liquid drop is formed by the same soap solution.

[@alphaiitd1]

Thanks sir