Surface area of a cylinder Watch

Ggdf
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#1
Report Thread starter 3 years ago
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Hi all

I'm currently trying to solve a problem in regard to this cylinder (dimensions: L = 10-2 m, d = 10-3 m and D = 2 × 10-3 m)

Name:  cylinder.jpg
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The question is:
Calculate the capacitance of the outer curved surface if the material has: Capacitance/surface area = 1.2 x 10-5 Fm2.
[Hint: capacitance is Cm = (Capacitance/unit area ) x (neuron surface area)] [Hint 2: circumference of a circle = 2pi x radius]


To answer this question, do I need to find the surface area of the outer cylinder? If so, to do this should I do the equation A = 2 π r h + 2 π r 2? Therefore take the capital d value (D = 2 × 10-3 m) and divide it by 2 to get the radius? Then should I plug this into the equation A = 2 π r h + 2 π r 2?
I'm confused because I also wonder whether I somehow need to use the value for the lower case d (d = 10-3 m)? Should I perhaps deduct this from the diameter of the upper case D as we only want the surface area of the hollow cylinder?

Please might anyone be able to advise me?

I'm very appreciative for any help.

Thank you very much
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brianeverit
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(Original post by Ggdf)
Hi all

I'm currently trying to solve a problem in regard to this cylinder (dimensions: L = 10-2 m, d = 10-3 m and D = 2 × 10-3 m)

Name:  cylinder.jpg
Views: 79
Size:  5.6 KB

The question is:
Calculate the capacitance of the outer curved surface if the material has: Capacitance/surface area = 1.2 x 10-5 Fm2.
[Hint: capacitance is Cm = (Capacitance/unit area ) x (neuron surface area)] [Hint 2: circumference of a circle = 2pi x radius]


To answer this question, do I need to find the surface area of the outer cylinder? If so, to do this should I do the equation A = 2 π r h + 2 π r 2? Therefore take the capital d value (D = 2 × 10-3 m) and divide it by 2 to get the radius? Then should I plug this into the equation A = 2 π r h + 2 π r 2?
I'm confused because I also wonder whether I somehow need to use the value for the lower case d (d = 10-3 m)? Should I perhaps deduct this from the diameter of the upper case D as we only want the surface area of the hollow cylinder?

Please might anyone be able to advise me?

I'm very appreciative for any help.

Thank you very much
You only want the outer curved surface so it is just 2.\pi.r.h
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Ggdf
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(Original post by brianeverit)
You only want the outer curved surface so it is just 2.\pi.r.h
Thank you very much for your help. I'm a little confused about how to go about this equation overall.

The information I've been provided to answer the question is:

Name:  Capitance.jpg
Views: 67
Size:  58.9 KB

And the question itself is:

Calculate the capacitance of the outer curved surface if the material has:
Capacitance/surface area = 1.2 x 10-5 Fm2.
[Hint: circumference of a circle = 2pi x radius]


The hollow cylinder is simply a model of a neuron and an understanding of neurons isn't required to answer the question. I think it's the wording that confuses me.

I'm unsure whether I need to multiply 1.2 x 10-5 Fm2 by 2 pi r h of the outer curved surface to answer the question?

I really appreciate your help.
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