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B Y : E R I C A P
Static electricity
Refers to the build-up of electric charge on the
surface of the objects.
It can be contrasted with current,electricity which
can be delivered through wires as a power
source.
There are 5 types of electric discharge (
Spark,Brush discharge,propagating brush
discharge,cone discharge and corona
discharged)
Lighting
RefuellingSparks from statics electricity can be dangerous when flammable vapour is present.
Operating TheatersDust and germs attracted by charged objects.We need to ‘earthed’ all the
equipment.
ComputersComputers require simillar ‘anti-static’ conditions as they are vulnerable to
electrostatic damage.
Uses of Static Electricity
Flue-ash precipitation
Photocopiers
Inkjet printers
Painting cars
Electric Current
→ is a flow of electric charge through a medium.
→ Charge typically carried by moving electrons such as wire.
→ The SI unit is AMPERE.
→ Is measured using AMMETER.
− Heating and lighting
− Magnetic
− Chemical
Series and Parallel circuits
Series current is the same at all the points in a series
circuits.
Parallel
The sum of the current in the branches of a parallel circuit equals the current entering or leaving the parallel section.
Potential Difference
* The difference in electric potential between two pointsin an electric field.
* measured in volts
* The work that has to be done in transferring unit positive change from one point to the other.
Resistance
The opposition of a conductor to current called RESISTANCE.
The formulae R=V/I
the smaller the I is for a given V,the greater R.
The ohm is the resistance of a conductor.
Ohm’s Law
Metallic Conductor (current through a metallic conductors is directly propotional to the voltage)(there are called ohmic or linear conductors)
Semiconductors diode
Filament Lamp
Variation of resistance with temperature
Variation of resistance with light intensity
In series same current flows through
each and total voltage.
In parallel the voltage between the
ends of each is the same.
Is a passive two terminals electrical
component used to store energy in electric
field.
its measured by farads(F)
Smaller units such as the microfarad are
more convenient.
A capasitors store electric charge and its
useful in many electric circuits
Practical capacitor
Polyester capacitor
Electrolytic capacitor
Charging
It can be charged by connecting a battery across it.During the charging,there is brief flow of lectrons round the circuits.A momentary current would be detected by a sensitive ammeter.
Discharging
When a conductor is connected across a charged capasitors,there is a brief flow of electron from the negatively charged plate to the positively one.
Electric Power
Is the rate at which electric energy is transferred by an electric circuits
The SI of power is watt
Electric lighting
Filament lampsIs a small coiled coil of tungsten wire,which
become white hot when current flows throught it.Its contain nitrogen and argon,not air.
Fluorescent stripsTransfer only 10% of the electrical energy supplied
to light; 90% becomes heat.
Compact Fluorescent lampsLast up to 8 times longer.used about 5 less energy
than others.
Electric heating
Heating elements
Three-heat switch
Fuses
Circuits in parallel
Switches and fuses
Staircase circuits
Ring main circuits
Fused plug
Earthing and safety
Circuits breakers
Double insulation
Danger of electricity
Electric shock
electric shocks occurs if current flows from an electric circuit through a person body’s to earth.Its causes by damaged insulation or faulty wiring.
Fire risks
How to AVOID!!
1. Switch off the electrical supply to an appliance before starting repairs.
2. Use plugs that have earth pin.
3. Do NOT allow appliances or cables to come into contact with water.
4. Do NOT have long cables trailing across room,under carpet or in other conditions.
5. Use plugs that have the correct fuse
6. Do NOT attach to many appliances to a circuit
7. Dont overload circuits by using to many adapters