# Surface area of a cylinder

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#1
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)

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?

I'm very appreciative for any help.

Thank you very much
0
6 years ago
#2
(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)

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?

I'm very appreciative for any help.

Thank you very much
You only want the outer curved surface so it is just
0
#3
(Original post by brianeverit)
You only want the outer curved surface so it is just

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

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?

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