2Electric CurrentElectric 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”
3Current flows from + to – Materials that Do Not allow current to flow through them are called “Insulators”Plastic, wood and rubber are insulators.
4Power SourcesA 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.
5A 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 BatteryThe current from a Battery flows in one direction and is called Direct Current (DC)
6Electricity 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
7Voltage, 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.
8Measurement Name Unit Symbol Ohm’s Law Voltage Volts V Current Amps A ResistanceOhmΩR
9Ohms Law This is how voltage, current & resistance are linked. Voltage V = I x RCurrent I = V/RResistance R = V/I
10Wiring a Plug Brown = Live Blue = Neutral Yellow/Green = Earth Pg 186 Fig 14.14Colour CodesA 3-Pin Plug
11Functions 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 BrownNeutral Wire is Blue
12SafetyThe Earth WireThe 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
13SafetyIf 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 safeEarth Rod
14Circuit BreakerHow Circuit Breakers Work: Circuit Breaker: At Work in Your HomeThe 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
15Parallel CircuitsIn 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.
16Series CircuitIt 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.
17Variable 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 anAlarm sounds if an LDR is placed in dark conditions. The problem could be considered as shown below.
18The alarm is an LED but it could be any output device.
19LEDLEDNote: we will look at how the transistor works later.