CAIE IGCSE Physics 4.5.6 The Transformer Topic Practice

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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

Question 1

[Maximum number: 6]

Question (a)

(a)

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

Fig. 7.2

Fig. 7.2

[ 6 ]

Question (i)

(i)

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 =

[ 3 ]

Question (ii)

(ii)

Draw a labelled diagram of a step-down transformer. On the labels, state a suitable material for each of the components.

[ 3 ]

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 ]

Question 3

[Maximum number: 1]

A transformer has 400 turns on the primary coil connected to the 240 V mains supply.
There are two secondary coils to serve different parts of a television. Secondary coil 1 has 2500 turns and secondary coil 2 has 20 turns.

Which row is correct?

p.d. across secondary coil 1/V

p.d. across secondary coil 2/V

12

3.2

1500

12

4200

12

4200

33

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