CAIE IGCSE Physics 4.5.6.7.100 Transformer Efficiency Ipvp Questions

Learn how conservation of power links transformer voltage and current, including efficiency and fuse limits.

Exam points

calculate primary or secondary current using transformer power relationships
apply conservation of power and efficiency to transformer calculations
determine fuse limits, load power and current in step-up or step-down transformers

[Maximum number: 3]

Fig. 7.2 shows a circuit diagram of a step-down transformer.

Fig. 7.2

The mains voltage supplied to the transformer is 240 V. The output power of the transformer is 45 W. The transformer is 100% efficient.

Calculate the input current to the transformer.
input current =

0.19 A
$I_{\mathrm{p}} V_{\mathrm{p}}=I_{\mathrm{s}} V_{\mathrm{s}}$ OR $\left(I_{\mathrm{p}}=\right) I_{\mathrm{s}} V_{\mathrm{s}} / V_{\mathrm{p}}$ OR $\left(I_{\mathrm{p}}=\right) 45 / 240$ OR $I_{\mathrm{p}} V_{\mathrm{p}}=45$ OR power in primary = power in secondary
$\left(I_{\mathrm{p}}=\right) 45 / 240$

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CAIE IGCSE Physics 4.5.6.7.100 Transformer Efficiency Ipvp Questions question 1