Paper 2 2008 No. 4

4. Diagram 4.1 shows a computer battery charger connected to a 240 Va.c. power supply. The battery charger contains box X and box Y.


(a) The function of the component in box X is to lower the voltage from 240 V a.c to 20 V a.c.

(i) Name the component in box X.

……………………………………… [1 mark]

(ii) Explain why a.c and not d.c is supplied in Diagram 4.1.

……………………………………….................................................................

……………………………………….................................................................

[1 mark]

(iii) State the physics concept which explains how the component in box X works.

………………………………………. [1 mark]

(b) The efficiency of the component in box X is 80%. Calculate the input current when the output power is 65 W.
[2 marks]

(c) Box Y contains four identified components to change a.c to d.c. On Diagram 4.2, draw the electronic components in the coloured circles provided.