Polythene rod gains electrons
If a woollen cloth is rubbed on it (becomes negatively charged
A perspex rod loses electrons
If it is rubbed by a woollen cloth (becomes positvely charged)
Earthing
Occurs when a charged object loses its charge to the earth through a conductor
Electric current
The flow of electric charge
Conductors
Substances which allow electric current flow through them freely
Insulators
Substances which do not allow electric current to flow through
Closed curcuit
Needed for the current to flow if there is a break in the current then the current won’t flow
Energy provided
A battery or power pack it is needed to move the current around the circuit
The battery pumps electrons
From its negative end around the circuit
The electrons are attracted
To the positive end of the battery
Potential difference
The difference in electrical pressure between the positive and negative ends of a battery/power pack
Whenever there is potential difference
Electricity will flow
This potential difference is known as voltage
And is measured in volts
Resistence
The opposition to the flow of electrons the unit is the Ohm and it is measured using a ohmeter
is placed in an eletric circuit it will slow down the flow of electrons
If a Resistor
Static electricity
A build up of electric charge that can occur on good insulators e.g polythene and perspex rods
Ohms law
Staes the voltage is directly proportional to current
Direct current/dc
It goes in one direction only e.g the current from a battery
Alternating current/AC
Changes very quickly many times a second
Mains supply
The electricity in our homes supplied by the ESB is A.C
Ring circuit
All households have a ring circuit made of live nuetral and earth wire
Sockets are tapped off at points along this ring circuit
Fuse
A safety device that prevents the ciruit from overheating it will melt when it is too hot breaking the circuit
Ciruit breaker
Limits the size of the current flowing in the current, a safety feature to prevent overheating but is based on magnetic effect of electricity
Live wire
Is brown and carries most electricity it is connected to to the plugs fuse on the right hand side
The neutral wire
Its blue and is connected to the left hand side
The earthwire
Is a safety wire no electricity flows in the earth wire unless the appliance it is attached to becomes “live” e.g toaster in this case the earth wire would carry the current to the earth instead of you electrocuting yourself should you touch the toaster
Watt
The unit of electrical power
The ESB charges a fee for the number of
Kilowatts (1000 watts) used per hour
ESB units of electricity
The kilowatt hour(kWh)
Kilowatt hour
The electrical energy used by a 1kW appliance running for an hour
Heating effect
Boil water in a kettle, immersion heater, electric cooker, fuse in plug
Chemical effect
Electroplating cheap metal with more expensive metal e.g silver, electrolysis(splitting) of water, mobile phone battery
Magnetic effect
Electromagnet made with a wire wrapped around a nail, electric motor, speakers, circuit breaker in fuse board
Electronics
The careful and exact control of tiny amounts of electric current
Diode
A component that will allow current to flow in one direction only
Forward biased
The positive end of a battery is connected to the positive end of a diode
Reverse bias
If the positive end of the battery is connected to the negative end of the diode, no electricity can flow
Diodes are used to …
Change alternating current into direct current
Electronic devices such as radios, tape recorders and calculators
Need low voltage direct current
Light emitting diode
A diode that gives out light when a current flows through it
Current will only flow when LED is
Forward biased
LED’s use only tiny currents
So a resistor must be connected in series with it
LED’s are useful because they are
Cheap, reliable and long lasting and use far less current than other light bulbs
LDR
Light dependent resistor whose reistance depends on light
When lights fall on an LDR
Its resistance decreases, this low resistance will allow a current throught the circuit