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CAIE IGCSE Physics Transformer Question Bank

Practise transformer construction and induction, calculate voltage, turns and current ratios and explain why high-voltage transmission reduces losses.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • explain how alternating current creates changing core flux that induces voltage in the secondary coil
  • use V_p/V_s = N_p/N_s and equal input–output power for ideal voltage and current calculations
  • explain that stepping voltage up lowers current for fixed power and reduces I squared R cable losses

Covered syllabus points

4.5.6.1—Construction of a simple transformer4.5.6.2—Terms primary, secondary, step-up and4.5.6.3—Transformer relation: Vp/Vs = Np/Ns4.5.6.4—Use of transformers in high- voltage4.5.6.5—Advantages of high-voltage4.5.6.6—Principle of operation of a simple4.5.6.7—100% transformer efficiency: IpVp =4.5.6.8—Recall/use: P = I2R to explain why

4.5.6 The transformer question 1

[Maximum number: 10]

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

Fig. 10.1

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.

Question (a)

(a)

Explain why there is a voltage between the two terminals of coil Q .

[ 3 ]

Question (b)

(b)

Explain why the core of the transformer is made of soft iron.

[ 1 ]

Question (c)

(c)

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

[ 2 ]

Question (d)

(d)

A heater is connected to coil Q. The current in the heater is 3.5 A. The transformer is 100% efficient.

Calculate the current in coil P.

current =
[ 2 ]

Question (e)

(e)

A transformer is used to step up the voltage before electrical energy is transmitted over long distances.

State and explain one economic effect of transmitting electrical energy at a high voltage.

[ 2 ]

4.5.6 The transformer question 2

[Maximum number: 8]

Question (a)

(a)

A transformer consists of two coils of wire wound on a core.

[ 4 ]

Question (i)

(i)

Suggest the material from which the two coils are made. State the reason for using this material.
material
reason

[ 2 ]

Question (ii)

(ii)

Suggest the material from which the core is made. State the reason for using this material.
material
reason

[ 2 ]

Question (b)

(b)

Fig. 8.1 represents the system of transmission of electrical energy from a power station to a home that is a long distance away.

Fig. 8.1

Fig. 8.1

[ 4 ]

Question (i)

(i)

State the difference between transformer X and transformer Y .

[ 1 ]

Question (ii)

(ii)

Explain why a very high voltage is used for transmission over large distances.

[ 3 ]
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