Resistivity Question
Q5.
(a) Give an expression for the resistivity of a material in the form of a uniform wire. Define all the symbols used.
(2 marks)
(b) A thin film of carbon may be used in some electronic systems. Typical dimensions of such a film are shown in the diagram.
![](5a.png)
(i) Calculate the resistance of the carbon film to a current I passing through it as shown above - resistivity of carbon = 4.0 × 10–5 Ω m
(ii) Without recalculating the resistance of the carbon film, explain how you would expect the resistance to change if the current flowed as shown below.
![](5b.png)
You should consider the numerical ratio or factor by which each dimension affecting the resistance has changed.
(4 marks)
(Total 6 marks)
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