Question regarding Electrical conduction(Resistance)

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In summary, the conversation discusses finding the resistance between two opposite edge faces of a square carbon film and the length of a carbon film on a curved insulator rod with a specific resistance. The relationship between the two questions is using the formula R = \frac{\rho l}{A} and solving for l. The phrase "curve surface" refers to the surface that is not the ends of a cylinder. By using the correct diameter of the rod, the problem can be solved by finding the cross-sectional area and length of the cylinder.
  • #1
Sanosuke Sagara
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(a) Find the resistance between two opposite edge faces of a piece of square carbon film of thickness 5.0 x 10^-7 n,if the resistivity of carbon is 4.0 x 10^-5 ohm meter.

(b) A carbon film of the same thickness is formed on an insulator rod of diameter 3.0m.What is the length of the rod so that the carbon film on its curve surface has a resistance of 100 ohm ?

Question (a) and (b) is continuous and I have no problem with question (a).My problem is question (b) and I can't really understand with the question and I can't imagine out the figure.

I want to ask whether there is any relationship of answers in question (a) in solving the qiestion (b) and I really need someone to explain to me the phrase 'curve surface' .

Thanks for anybody that spend some time on this question and I really need explanation for this question.
 
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  • #2
Think of a cylinder, the curved surface is well, the surface that isn't the ends.

Could you not just use the formula, [tex]R = \frac{\rho l}{A}[/tex] and solve for l? R is the resistance, [itex]\rho[/itex] is the resistivity and A is the cross sectional area.
 
  • #3
Solution and some suggestion to solve the question

I have try to solve this question for a long time and I really can't find the correct answer.I have my doubt,solution to the question in the attachment that followed.Thanks for anybody that spend some time on this qustion.
 

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  • #4
Sanosuke Sagara said:
I have try to solve this question for a long time and I really can't find the correct answer.I have my doubt,solution to the question in the attachment that followed.Thanks for anybody that spend some time on this qustion.
Judging by your attached document, the correct diameter of the rod in part b) is 3.0 mm, rather than 3.0m. Using 3.0 mm the given answer is realized by following exactly the same approach I suggested in your previous problem. Find the resistance from one end to the other of a thin walled cylinder by finding the cross-sectional area of the cylinder walls, and the length of the cylinder. Here you know the resistance and must solve for the length.
 
  • #5
Thanks for your help OlderDan and I really appreciate it because I have really understand with the question and thanks for your explanation.
 

What is electrical conduction?

Electrical conduction is the movement of electrically charged particles, such as electrons, through a conducting material.

How is resistance related to electrical conduction?

Resistance is a measure of how difficult it is for electrically charged particles to flow through a material. In other words, it is the opposition to the flow of electricity.

What factors affect resistance in a material?

The factors that affect resistance in a material include the type of material, its length, cross-sectional area, and temperature. The type of material determines how easily electrons can flow through it, while the length and cross-sectional area affect the amount of space available for electrons to move. Temperature also plays a role, as an increase in temperature can result in an increase in resistance.

How is resistance measured?

Resistance is measured in ohms (Ω) and can be calculated using Ohm's Law, which states that resistance is equal to voltage divided by current (R = V/I). It can also be measured using a multimeter, which measures the voltage and current in a circuit and calculates the resistance.

What are some real-life applications of electrical conduction and resistance?

Electrical conduction and resistance are important concepts in many everyday devices. They are used in the wiring of buildings, electronic devices, and power transmission systems. They are also critical in the design of electrical circuits for various applications, such as lighting, heating, and communication systems.

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