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Resistivity Question

Q4.

(a) A sample of conducting putty is rolled into a cylinder which is 6.0 × 10–2 m long and has a radius of 1.2 × 10–2 m. The resistivity of the putty is 4.0 × 10–3 Ωm.

(i) Calculate the resistance between the ends of the cylinder of conducting putty. Your answer should be given to an appropriate number of significant figures.

(4 marks)

(ii) The putty is now reshaped into a cylinder with half the radius and a length which is four times as great. Determine how many times greater the resistance now is.

(2 marks)

(b) Given the original cylinder of the conducting putty described in part (a), describe how you would use a voltmeter, ammeter and other standard laboratory equipment to determine a value for the resistivity of the putty. Your description should include:

  • a labelled circuit diagram,
  • details of the measurements you would make,
  • an account of how you would use your measurements to determine the result,
  • details of how to improve the precision of your measurements.

(8 marks)

(Total 14 marks)