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2 marksElectrical Quantities

CAPE Physics Unit 2 · 2005 · Paper 2 · Question 6(b)(iv)

A step-up ideal transformer connected to a 240-V r.m.s. a.c. supply powers an 18 kV r.m.s. neon sign, protected by a primary fuse that blows when secondary current exceeds 10 mA.

Calculate the current rating of the fuse to be used in the primary circuit.

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Other parts of this question

  1. 6(a)Draw a labelled diagram of a transformer suitable for transforming from 240 V a.c. to 12 V a.c. Give details of the materials used in its structure and reasons…[8 marks]
  2. 6(b)(i)Calculate the peak value of the primary voltage.[2 marks]
  3. 6(b)(ii)Calculate the turns ratio N_p / N_s of the transformer.[2 marks]
  4. 6(b)(iii)Calculate the power that must be supplied to the transformer when the secondary current is 10 mA.[2 marks]
  5. 6(c)Calculate what percentage of the power transmitted is lost in the cables.[4 marks]

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