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7 May 2007 13:22:58 IST

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Soap bubble

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If a soap bubble ,having radius r, is charged to a charge density and its radius is increased to R ,then R is equal to ................. [ T is the surface tension ]

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NIVE PAUL

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8 May 2007 07:02:51 IST

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hey..i hav a quest on soap bubble too..if neone noes d ans ..plzz....if a soap bubble is givn a -ve charge its rad will inc/dec/remain same???

Asmita Bhattacharya

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8 May 2007 12:40:12 IST

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????

Ankit Sagwal

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8 May 2007 12:50:45 IST

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ok, let me think over it
give me 5 min...................

Ankit Sagwal

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8 May 2007 12:58:10 IST

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is the ans something like
R^3 = (sigma)^2 * r^4 / 4*E0*T
where E0 is epsilon
tell me, so that i can know if i m on the right track

Asmita Bhattacharya

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8 May 2007 13:02:43 IST

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No its not..............

howevr thanx 4 giving it a try..........

Ankit Sagwal

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8 May 2007 13:03:59 IST

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tell me the ans. then
it should be related to it..............

Asmita Bhattacharya

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8 May 2007 13:09:31 IST

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R= 8 Eo T/

Manasi

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8 May 2007 13:16:11 IST

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here's nothing...

the electrostatic pressure on a bubble when a charge density

is given to a bubble of radius R =

² / 2

₀

so equating it with 4T / R , we have R = 8

₀ T/

Himanshu

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8 May 2007 13:19:40 IST

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fr that -ive charge qs , radius of soap bubble will always increase whether it is given +ive or -ive charge.........

Manasi

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8 May 2007 13:27:07 IST

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for any small area dS on the sphere, net E = 0

thus E1 + E2 = 0 (in vector form)

=> |E1| = |E2|

now field lines will be almost perpendicular to dS

thrfore at dS

E A = A

₀

=> E =

₀

=> E1 = E2 =

/ 2

₀

thrfore force on dS = dq E

= (

dS ) (

/ 2

₀)

=> P = F/ dS = ² / 2 ₀

twinkle dream

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9 May 2007 13:55:14 IST

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hey himanshu can u plz explain y will it always increase?

Utkarsh Sinha

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9 May 2007 14:06:58 IST

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The surface has the same kind of charge... so each part will repel... so the radius should always increase

Himanshu

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9 May 2007 14:14:27 IST

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lemme correct a little

charge gets deposited on the surface (the charge we give)
so it will repel and radius will increase

cheeersss

J Sundararajan

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13 May 2007 09:06:46 IST

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radius of soap bubble increases on account of mutual repulsion between elementary charges on surface of bubble.

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