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STATIC ELECTRICITY STATIC ELECTRICITY
Have you ever stuck a balloon to the wall Have you ever stuck a balloon to the wall after rubbing it on your head?after rubbing it on your head?
Has your sweatshirt ever made crackling Has your sweatshirt ever made crackling noises when you took it off?noises when you took it off?
Have you ever got an electric shock off Have you ever got an electric shock off your door knob?your door knob?
Have you ever seen lightening?Have you ever seen lightening?
All these things happen because of
Static Electricity
What is Static Electricity?What is Static Electricity?
Static electricity occurs when there is a Static electricity occurs when there is a build up of electric charge on the surface build up of electric charge on the surface of a material.of a material.
It is called static electricity because the It is called static electricity because the charges don’t move.charges don’t move.
The electricity we use everyday involves The electricity we use everyday involves moving charges.moving charges.
What is charge?What is charge?
To understand charge we have to look at To understand charge we have to look at things on an extremely small scale.things on an extremely small scale.
We have to try and understand things that We have to try and understand things that we can’t even see with the most powerful we can’t even see with the most powerful microscope.microscope.
Atoms!
What is inside the atom?What is inside the atom?
The atom is made of 3 sorts of particles.The atom is made of 3 sorts of particles.
The electron The electron
The protonThe proton
The neutronThe neutron
We can imagine each as a tiny little ball. We can imagine each as a tiny little ball.
ChargeCharge
The electron is negatively charged.The electron is negatively charged. The proton is positively charged.The proton is positively charged. The neutron has no charge, it is neutral. The neutron has no charge, it is neutral.
How do charges behave?How do charges behave?
What do you know about magnets?What do you know about magnets?
2 north poles will repel each other, but a 2 north poles will repel each other, but a north and a south put together will attract north and a south put together will attract one another.one another.
Law Law of Attraction and Repulsionof Attraction and Repulsion
opposites attract, likes repel.opposites attract, likes repel.
How do charges behave?How do charges behave?
Exactly the same thing happens with Exactly the same thing happens with charges.charges.
2 positive charges put together will repel 2 positive charges put together will repel each other.each other.
Put a positive charge near a negative Put a positive charge near a negative charge and they will attract each other.charge and they will attract each other.
A charged object may even attract a A charged object may even attract a neutral one.neutral one.
Static electricityStatic electricity
Static electricity is caused when certain Static electricity is caused when certain materials are rubbed against each other.materials are rubbed against each other.
Electrons can be rubbed off one material Electrons can be rubbed off one material and on to another. and on to another.
The material that has got extra electrons is The material that has got extra electrons is now negatively chargednow negatively charged
The material which has lost electrons is The material which has lost electrons is positively charged.positively charged.
Seeing the effects of charge: Seeing the effects of charge: the electroscopethe electroscope the electroscope is a the electroscope is a
simple device for simple device for observing the presence observing the presence of electric chargeof electric charge
it consists of a small it consists of a small piece of metal foil (gold piece of metal foil (gold if possible) suspended if possible) suspended from a rod with a metal from a rod with a metal ball at its topball at its top
• If a negatively charged rod is placed near the ball, the electrons move away because of the repulsion. The two sides of the metal foil then separate.
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Static electricityStatic electricity
It is this imbalance of positive and It is this imbalance of positive and negative charges that causes:negative charges that causes:
Balloons to stick to walls.Balloons to stick to walls.Your hair to stand on end when brush your Your hair to stand on end when brush your
hair on a dry day.hair on a dry day.And the electric shock you sometimes get And the electric shock you sometimes get
from the door handle.from the door handle.
Making Sparks:Making Sparks:The Van de Graff GeneratorThe Van de Graff Generator
The van de Graff generator The van de Graff generator is a device for building up a is a device for building up a large electrical charge on a large electrical charge on a metal sphere. metal sphere.
The charge is generated The charge is generated by friction between a by friction between a rubber belt and a roller.rubber belt and a roller.
the charge on the belt is the charge on the belt is transferred to the sphere transferred to the sphere by a brush. by a brush.
Danger High Voltage !Danger High Voltage ! The van de Graff can The van de Graff can
charge the sphere to charge the sphere to 50,000 volts!50,000 volts!
This is enough to This is enough to cause discharges to cause discharges to the surrounding airthe surrounding air
The sparks excite air The sparks excite air molecules which give molecules which give off lightoff light
Conductors and Conductors and InsulatorsInsulators
In conductors, electric charges are free to move In conductors, electric charges are free to move through the material. In insulators, they are not.through the material. In insulators, they are not.
In conductors:In conductors: The charge carriers are called free electronsThe charge carriers are called free electrons Only negative charges are free to moveOnly negative charges are free to move When isolated atoms are combined to form a metal, When isolated atoms are combined to form a metal,
outer electrons of the atoms do not remain attached outer electrons of the atoms do not remain attached to individual atoms but become free to move to individual atoms but become free to move throughout the volume of the material.throughout the volume of the material.
Revisit thermal energy what type of materials were Revisit thermal energy what type of materials were good conductors of thermal energy? good conductors of thermal energy?
Conductors and InsulatorsConductors and Insulators
Conductors:Conductors:
Allow a free flow of Allow a free flow of electrons.electrons.
Ex. MetalsEx. Metals
(the wire inside an (the wire inside an electrical cord)electrical cord)
Insulators:Insulators:
Slow or stop the flow Slow or stop the flow of electrons.of electrons.
Ex. Ex. Rubber, Rubber, Glass, Glass, PlasticPlastic
(the rubber coating on (the rubber coating on the outside of an the outside of an electrical cord)electrical cord)
What causes lightning?What causes lightning?
Lightning is actually Lightning is actually just static electricity just static electricity on a much larger on a much larger scale.scale.
The rubbing is caused The rubbing is caused by air moving aroundby air moving around
In thunderclouds In thunderclouds bottom is usually bottom is usually negative and top is negative and top is positive.positive.
Interesting factsInteresting facts
Lightning bolts can travel at speeds of up Lightning bolts can travel at speeds of up to 60,000 miles per second.to 60,000 miles per second.
Every second around 100 bolts of lightning Every second around 100 bolts of lightning strike the Earth.strike the Earth.
One lightning bolt has enough electricity to One lightning bolt has enough electricity to power 200,000 homes. power 200,000 homes.
You are more likely to be struck by You are more likely to be struck by lightning than be eaten by a shark.lightning than be eaten by a shark.
