8      (a) The transformer in Fig. 8.1 is used to convert 240 V a.c. to 6 V a.c.

primary           secondary coil coil

(480 turns)

Fig. 8.1

                  (i) Using the information above, calculate the number of turns on the secondary coil.

            number of turns =  ................................................ [2]                      (ii) Describe how the transformer works.

 ..................................................................................................................................

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 ..................................................................................................................................

 ..................................................................................................................................

 ............................................................................................................................ [3]

                         (iii) State one way in which energy is lost from the transformer, and from which part it is lost.

 ............................................................................................................................ [1]

        (b) Fig. 8.2 shows a device labelled “IGCSE Transformer”.

Fig. 8.2

               Study the label on the case of the IGCSE Transformer.

(i)           What is the output of the device?  ....................................................................... [1]

(ii)          From the information on the case, deduce what other electrical component must be included within the case of the IGCSE Transformer, apart from a transformer.

 ............................................................................................................................ [1]

 (c) A transformer supplying electrical energy to a factory changes the 11 000 V a.c. supply to 440 V a.c. for use in the factory. The current in the secondary coil is 200 A.

                Calculate the current in the primary coil, assuming no losses from the transformer.

                                                                                      current =  ................................................ [2]

[Total: 10]

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9 (a) Fig. 9.1 illustrates the left hand rule, which helps when describing the force on a currentcarrying conductor in a magnetic field.

thumb

Fig. 9.1

                One direction has been labelled for you.

                In each of the other two boxes, write the name of the quantity that direction represents.

[1]

         (b) Fig. 9.2 shows a simple d.c. motor connected to a battery and a switch.

Fig. 9.2

(i)        On Fig. 9.2, write in each of the boxes the name of the part of the motor to which the arrow is pointing.             [2]

(ii)       State which way the coil of the motor will rotate when the switch is closed, when viewed from the position X.

 ............................................................................................................................ [1]

(iii)     State two things which could be done to increase the speed of rotation of the coil.

1. ...............................................................................................................................

2. ......................................................................................................................... [2][Total: 6]

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