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5 marksAlternating Currents

CAPE Physics Unit 2 · 2003 · Paper 2 · Question 7(c)(ii)

A transformer on a utility pole operates at 8.5 kV_rms on the primary side and supplies electrical energy to nearby houses at voltage of 120 V_rms. Assume that the transformer is ideal.

The average rate of energy consumption in the houses served by the transformer is 78 kW. Calculate the peak value of the current in BOTH windings of the transformer.

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Other parts of this question

  1. 7(a)(i)State the relationship between peak voltage, V_p, and root mean square voltage, V_rms, for an alternating sinusoidal voltage.[1 mark]
  2. 7(a)(ii)Calculate the value of the direct current that will produce the same quantity of thermal energy in a particular resistor, as an alternating current that has a…[2 marks]
  3. 7(b)Explain the operation of an ideal transformer when a small alternating voltage is supplied to its primary winding.[7 marks]
  4. 7(c)(i)Calculate the turns ratio, N_p / N_s, of the transformer.[2 marks]
  5. 7(c)(iii)Calculate the resistive load in the secondary circuit of the transformer.[3 marks]

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