1. Electricity & Electronics
LCA 1
Session 2

2. Electric Current
Electric Current is produced when electrons move through a material.
Metals have free electrons so that is why electricity can travel through metals.
Materials that allow electricity to flow through them are called “ Conductors”

3. Current flows from + to –
Materials that Do Not allow current to flow through them are called “Insulators”
Plastic, wood and rubber are insulators.

4. Power Sources
A power source is needed to push the electrons around the circuit.
This pressure is called electromotive force or e.m.f. It is measured in Volts (V)
It is like a pump pushing water, the Voltage pushes current.

5. A Battery A Battery is made up of cells. Each cells gives 1.5V
So if a Battery has 4 cells that means X 1.5=6V Battery
The current from a Battery flows in one direction and is called Direct Current (DC)

6. Electricity Supply Company
In Ireland there is “Electric Ireland” (ESB), “Bord Gais” and “Airtricity”
These companies supply Alternating Current (AC).
The flow changes direction 50 times every second. + to – then – to +.
They supply 220V

7. Voltage, Current & Resistance
Every circuit has to have voltage, current and resistance.
Resistance is what tries to stop current flow.
Some conductors are made to have some resistance and these are called resistors.

8. Measurement Name Unit Symbol Ohm’s Law Voltage Volts V Current Amps A
Resistance
Ohm Ω R

9. Ohms Law This is how voltage, current & resistance are linked.
Voltage V = I x R
Current I = V/R
Resistance R = V/I

10. Wiring a Plug Brown = Live Blue = Neutral Yellow/Green = Earth
Pg 186 Fig 14.14
Colour Codes
A 3-Pin Plug

11. Functions of the wires.
The function of the Brown wire which is called the Live is to bring the current from the power station to the appliance that you are using.
The function of the Blue wire which is called the Neutral is to return the current to the power station from the appliance that you are using.
Live Wire is Brown
Neutral Wire is Blue

12. Safety
The Earth Wire
The metal body of electric appliances is connected to the earth by means of earth wire so that any leakage of electric current is transferred to the ground. This prevents any electric shock to the user. That is why earthing of the electrical appliances is necessary

13. Safety
If for whatever reason there is a fault, all the metal parts of the electrical appliance may carry current which means there is the danger of electric shock.
The earth takes the current to ground and makes the appliance safe
Earth Rod

14. Circuit Breaker
How Circuit Breakers Work: Circuit Breaker: At Work in Your Home
The circuit breaker is an absolutely essential device in the modern world, and one of the most important safety mechanisms in your home.
Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem.
Without circuit breakers (or the alternative, fuses), household electricity would be impractical because of the potential for fires and other mayhem resulting from simple wiring problems and equipment failures

15. Parallel Circuits
In a parallel circuit each bulb gets a + and a -. Therefore as seen in the diagram the power supply is a 9V battery, this means each bulb gets 9V and if one blows the others will light.

16. Series Circuit
It a series circuit each bulb is wired after the previous one. As the diagrams show the Voltage is 120V so each bulb gets 60V.
If one bulb blows it will break the circuit.

17. Variable Resistor Potential Divider
The potential divider forms the basis of many electronic circuits and allows us to use a variety of Sensors such as LDRs (light), thermistors (heat) and moisture probes etc. The process can be thought of as three distinctive parts or blocks. Let us take as an example a situation whereby an
Alarm sounds if an LDR is placed in dark conditions. The problem could be considered as shown below.

18. The alarm is an LED but it could be any output device.

19. LED
LED
Note: we will look at how the transistor works later.

22. Variable Resistor
With this device we can create a potential difference
Because it has 3 legs and it’s resistance can be changed manually.

25. Transistor A Transistor is a an electronic switch
It has 3 legs Collector, base & emitter
Current will only flow through it if there is 0.7V at the base.
So it is turned on and off electronically.

26. Transistor
0.4V
V is above 0.7 = Lights
V is below 0.7 = unlit

27. 2013

28. 2012

29. 2011

30. 2010 Resistor- Slows down the flow of current
Transistor- Is an electronic Switch

31. 2009
1 Resistor
2 Buzzer
Light Dependant Resistor- Resistance changes with changes in light.

32. 2008
LED
Transistor
Switch
Buzzer

33. 2006

34. 2007
C Switch
D Resistor
9V is the power of the battery, Voltage is the force it’s pushing the current around the circuit with.

35. 2006
A = 2
B= 1
A=LED –Indicator
B=Transistor-Switch

36. 2005 1.=Variable Resistor 2.=Resistor 3.=Transistor 4.=Bulb
Thermister – resistance changes with changes in heat.

37. 2004

38. 2003

39. 2002

40. 2001