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GCSE Standard Questions: The Generator

Q4. The diagram shows a student's design for a simple wind speed gauge.

(a) Explain why the wind causes the a.c. voltmeter to give a reading. The explanation has been started for you.

The wind causes the plastic cups to turn. This causes the spindle and magnet to turn. The (magnetic) field / lines of force / flux rotate(s) / move(s) / through / in / cut(s) the coil No credit is given for the idea that movement 'creates' the magnetic field - it must be clear that flux lines are cut.

A potential difference / p.d. / voltage is then induced (key word - must be in there!) across the coil No marks for talk of current - you are asked about voltmeter reading!

(2 marks)

(b) The gauge is not sensitive enough to measure light winds. Suggest one way that the design can be modified to make the gauge more sensitive.

any one from:

  • more powerful / stronger / lighter magnet (NOT bigger - you can have a big weak magnet and a strong small one!)
  • larger / more / bigger / lighter cups / with a bigger aperture area
  • longer arms
  • lubricate the spindle
  • add more turns to the coil / nail

(1 mark)

(Total 3 marks)