1. Term 4

2. Unit 1: Electrical Systems
1.1 Simple circuit components
In every system an electrical circuit has three components
Input
Process
Output
Can you think of examples of each?

3. Unit 1: Electrical Systems
1.2 Input devices
Input devices can be described as:
a device that put electrical energy into a circuit
the environment can provide energy
Input devices that we will look at are:
Electrochemical cell (battery)
Generator
Solar panel

4. Unit 1: Electrical Systems
1.2.1 Electrochemical cell (battery)

5. Unit 1: Electrical Systems
1.2.1 Electrochemical cell (battery)
What is an electrochemical cell?
It is a device that uses a chemical reaction to create electrical energy
What is electrolyte?
It is a liquid or gel that contains ions
What is an electrode?
It is a solid electric conducting metal, it can be positive or negative
Negative electrode is called a cathode
Positive electrode is called an anode

6. Unit 1: Electrical Systems
1.2.1 Electrochemical cell
What are the components of a electrochemical cell?
Electrode of zinc (positive electrode - anode)
Electrode of copper (negative electrode – cathode)
Two glass buckets filled with electrolyte

7. Unit 1: Electrical Systems
1.2.2 Generator
What is a generator?
Is a machine that converts mechanical energy into electrical energy
It is a machine that converts wind energy into electrical energy
Disadvantages of generators:
Wind generators need wind
Birds can destroy the blades
Diesel generators can be expensive
Diesel generators are heavy

8. Unit 1: Electrical Systems
1.2.2 Generator

9. Unit 1: Electrical Systems
1.2.3 Solar panel (photovoltaic cell)
What is a solar panel?
It converts light energy into direct current
Disadvantages of solar panels?
They only operate in sunny climates
Hail can damage it
Panels can be vandalised
They are expensive

10. Unit 1: Electrical Systems
1.2.3 Solar panel (photovoltaic cell)

11. Unit 1: Electrical Systems
Process Devices
What is a process device?
it takes the electrical current and changes it before it reaches the output devices
Process devices are:
resistors

12. Unit 1: Electrical Systems
1.3.1 Resistors
All materials can be grouped in three categories:
Insulators
Semi-conductors
Conductors

13. Unit 1: Electrical Systems
1.3.1 Resistors
What is an insulator?
A material that cannot conduct electricity
What is a semi-conductor?
A material that opposes the flow of electricity
What is a conductor?
A material that allows the free flow of electricity

14. Unit 1: Electrical Systems
1.3.1 Resistors
What are the uses of a resistor?
They limit the current
They cause a drop in voltage
They generate heat
Resistance is measured in ohms and is determined by four important factors:
The type of material
How long the material is
The area of the cross-section
The temperature of the material

15. Unit 1: Electrical Systems
1.3.2 Lamp
What is a lamp?
It is a device that converts electrical energy into light and heat
Disadvantages of a lamp:
Some must not be touched when it is burning
Some lamps can heat up a room

16. Unit 1: Electrical Systems
1.3.3 Heater
What is a heater?
It is a devices that converts electrical energy into heat
Disadvantages of heaters:
They can be dangerous
They are expensive
They use a lot of electricity
Can cause fires
They dry out the air

17. Unit 1: Electrical Systems
1.3.4 Buzzer
What is a buzzer?
It is a devices that converts electrical energy into sound
Disadvantages of a buzzer:
The sound can be irritating
The sound will not carry far distances

18. Unit 1: Electrical Systems
1.3.5 Motor
What is a motor?
It is a device that converts electrical energy into movement

19. Unit 1: Electrical Systems
1.4 Control Devices: Switches
What is a switch?
It is a device that puts electrical energy into a circuit
There are different types of switches:
Push switch
SPST switch
SPDT switch
DPDT switch

20. Unit 1: Electrical Systems
2. Correct connections: Short circuits
What is a short circuit?
It is a low resistance in a circuit
Or a weak point in the circuit
Short circuits prevent the follow of electricity

21. Unit 1: Electrical Systems
3. Electrical components See the table on page 161 You must learn the whole table

22. Unit 3:Electrical systems and control
Batteries and bulbs in parallel
Advantages
Disadvantages
Has the same current all around the circuit
If one bulb stops working the other will still work

23. Unit 3:Electrical systems and control
Batteries and bulbs in series
Advantages
Disadvantages
Can add more power
Increase the resistance
If one bulb stops working all will go out

24. Unit 3:Electrical systems and control
4. Photovoltaic cells
What is photovoltaic cell?
It is a solar panel

25. UNIT 3: PHOTOVOLTAIC CELLS
Advantages of a photovoltaic cell:
Produce pollution free energy Can be used for years with little maintenance
Useful for areas that don’t have electricity
Sun shine is always available
Save you a lot of money
Disadvantages:
It costs a lot to install
Will not work well if weather is cloudy for long period of time

26. Unit 4:Electrical systems and control
1.Thermal power stations

27. Unit 4:Electrical systems and control
2. Nuclear energy

28. Unit 4:Electrical systems and control
3. Solar energy

29. Unit 4:Electrical systems and control
4. Hydroelectric power stations

30. Unit 4:Electrical systems and control
5. Wind-driven turbines

31. Unit 4:Electrical systems and control
6. Alternating current
6.1 Step-up and step-down transformers
6.2 Distributing electric power across the country
6.3 National grid

32. Unit 4:Electrical systems and control

33. Unit 4:Electrical systems and control