1. Electrical Energy Sources

2. Household appliances

3. Power ratings of appliances
Clock 10W
Table lamp 100W
Drill W
Iron kW
Kettle kW
Immersion heater 3.0kW
Cooker kW

4. Power Rating Label Frequency 50 Hz Voltage 230V ~ Double insulated
Power 2000W

5. Power Rating Plate Model BD 760K Drill Model 4597 iron 230V ~ 50 Hz
Made in Spain
Model 4597 iron
230 V ~ Hz
1200 W
Made in UK

6. What’s the difference?

7. Flexes and Power Power rating Typical appliance Conductor thickness
Maximum current
Up to 700W
Clock, food mixer
0.50 mm2 3A
700 –
1380 W
Hair dryer; toaster
0.75 mm2 6A
1380 – 2300W
Kettle, fan heater
1.00 mm2
10A W
3kW heater
1.25 mm2
13A

8. Fuses and safety

9. Plugs and fuses
Metal contact
Thin wire
casing
Fuse symbol

10. Fuses must be connected to the live terminal
Live 230V
Neutral 0V
Live 230V
Neutral 0V
If fuse blows lamp is only connected to neutral (0V) so is safe
If fuse blows lamp is still connected to live and so is at a high voltage
The same principle applies to switches. Switches must always be connected to the live terminal.

11. Extension lead wiring
Earth
Live
Live
Neutral
Neutral

12. Light socket wiring

16. What’s the difference?

17. What’s the difference? 230V A.C. Can be fatal, continuous supply
1.5V D.C. Safe, runs out

18. Direct Current (DC)
+ve
+ve
-ve
-ve
Cells are typically 1.5V DC

19. Time base ms/division
AC/DC switch 0V
Y axis
V/div

20. Direct Current
+ 6V
- 6V
Connections reversed
Y input positive

21. Alternating Current
The mains supplies 230V AC (Alternating Current) 50Hz

22. Alternating Current
Mains current cycles from positive to negative 50 times per second (50Hz)
Signal pattern is the same independent of how the leads are connected

23. Alternating Current
8V peak
Vpeak = √2 Vmeasured
Multimeter 5.8V

24. AC and DC
A cell or battery provides direct current (DC). The electrons always flow in the same direction (negative to positive). A typical cell has a voltage of 1.5V.
If the electricity supply is AC (alternating current) the current constantly changes direction. Mains electricity is 230V AC at 50Hz. This means that the current cycles from positive to negative 50 times per second.
The measured AC voltage is less than the peak voltage (by a factor of √2). This is called the RMS (root mean square) value.