CAIE IGCSE Physics 4.5.6.3 Transformer relation: Vp/Vs = Np/Ns

Practise using Vp/Vs = Np/Ns to calculate voltages, turns and turns ratios for primary and secondary transformer coils.

Exam points

calculate Vs, Vp, Ns or Np by substituting values into Vp/Vs = Np/Ns
use a turns ratio to decide whether a transformer steps voltage up or down
interpret transformer diagrams with labelled coil turns and input or output voltages

[Maximum number: 2]

Fig. 10.1 shows a transformer that consists of two coils P and Q, and an iron core.

Fig. 10.1

There are 200 turns on coil P and 340 turns on coil Q.

A4.0 V a.c. power supply is connected to coil P.

Calculate the voltage between the two terminals of coil Q .
voltage =

$\left(V_{S}=\right) V_{P} \times N_{S} \div N_{P}$ OR $4.0 \times 340 \div 200$

C1

6.8 V

A1

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