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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.

(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.

You should consider the numerical ratio or factor by which each dimension affecting the resistance has changed.

(4 marks)

(Total 6 marks)