Electricity

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