2. Class exercise 1 Find the equivalent resistance of the following circuit.

3. Class exercise 2 Find the equivalent resistance of the following circuit.

4. Class exercise 3(P.160#5a) 2  1  4  3  AB D C The resistance across AB is: 1  4  3  2 

5. Class exercise 4(P.160#5e) 2  1  4  3  AB D C The resistance across AC is: 1  4  3  2 

6. Class exercise 5(P.160#6)

7. Class exercise 6 e.m.f. of the battery = 12 V 100  XY Z (a) What is the potential difference across X and Z? (b) What is the potential difference across X and Y? (c) What is the potential difference across Y and Z?

8. Class exercise 6 e.m.f. of the battery = 12 V 100  XY Z (d) What is the current flowing out from the battery? (e) What is the current flowing from X to Y? (f) What is the current flowing from Y to Z via the upper and lower resistor?

9. Class exercise 7 e.m.f. of the battery = 12 V 120  200  300  XY Z (a) What is the current flowing out from the battery? (b) What is the current flowing from X to Y? (c) What is the current flowing from Y to Z via the upper and lower resistor?

10. Class exercise 8(P.161#9)

11. Electrical Power The rating on a lamp is ‘220 V / 1000 W’. What does it mean?

12. Electrical Power This means when the lamp is operated normally, that is, when the voltage supplied to the lamp is 220 V, then the lamp consumes electrical energy at a rate of 1000 W. Under normal state, the electrical energy consumed by this lamp in 1 hour is 1 kWh. 1 kWh = 1000  3600 J = 3600000 J

13. L,N,E socket Green and yellow blue brown

14. Ring circuit N E L

15. Fuses Symbol for fuse Fuse wire is connected with the live wire. When the current is above the safety limit, the fuse will blow and the live wire is cut off from the mains supply.

16. Symbol for double insulation

17. Class exercise 10

18. Class exercise 11(P.185#9) I

19. Class exercise 12P.185#11) The lamps are connected in parallel instead of in series for: (1)The lamps can be operated separately. (2) If one lamp is damaged, the other lamps can still function.

20. Earthing  

22. Overloading Do not overload a universal adaptor.

23. Damaged wires Do not touch the damaged wires. Repair the damaged wires.

24. Damaged wires Do not pull a plug out from a socket by holding the wire only

25. Don’t touch the switch with wet hands Do not operate a switch with wet hands.

26. Don’t use electric appliances in bathroom Do not use electric appliances in the bathroom via an extension cable.