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4 marksElectrical Quantities

CAPE Physics Unit 2 · May/June 2025 · Paper 2 · Question 1(a)(iii)

This question explores the electrical properties of metals and the measurement of resistivity.

A DC generator supplies a current of 10 A to a load through a distribution line. The distribution line is a solid copper conductor of diameter 2.0 mm. The free electron density in copper at room temperature is 8.5 × 10^28 m^-3. Calculate the drift velocity of the electrons in the distribution line.

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Other parts of this question

  1. 1(a)(i)Explain, in terms of electron movement, how drift velocity occurs in metals.[4 marks]
  2. 1(a)(ii)Consider a cylindrical piece of metal of length, d, cross-sectional area, A, and number density of charges, n. Derive the equation relating current in the…[5 marks]
  3. 1(b)(i)On the grid provided in Figure 1 on page 7, plot a graph of voltage drop versus length. Draw the line of best fit through the points.[4 marks]
  4. 1(b)(ii)Determine the gradient of your graph in (b)(i).[3 marks]
  5. 1(b)(iii)Derive an expression for the gradient in terms of ρ, the resistivity of the wire.[3 marks]
  6. 1(b)(iv)Hence, determine ρ, the resistivity of the unknown metal.[2 marks]
  7. 1(b)(v)Calculate the power dissipated by the wire during the experiment.[1 mark]
  8. 1(b)(vi)Calculate the energy drawn from the power supply if the experiment runs for a total of 15 minutes.[3 marks]
  9. 1(b)(vii)State ONE assumption made about the wire in the experiment.[1 mark]

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