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11 Electrostatics

Edexcel IGCSE Electrostatics

E Allcoat

on 16 September 2014

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Transcript of 11 Electrostatics


Your photocopier or Xerox machine uses static electricity to copy print to a page.
The ink is given an electrical charge so that it will stick to the paper in the designated areas.
Alternatively, the drum is charged as well as the ink, allowing transferal to the paper.

Rub a plastic rod with a duster and hold it near some scraps of paper.
Write down in your exercise book:

Answer the following question in your exercise book:

a plastic rod
a duster
a few small pieces of paper

Some people purchase what are called air ionizers to freshen and purify the air in their homes.
They work on a similar principle as the smokestack pollution control.
These devices strip electrons from smoke molecules, dust particles, and pollen in the air, just as what happens in creating static electricity.
These charged dust and smoke particles are then attracted to and stick to a plate on the device with the opposite charge.
After a while, much of the pollution is drawn from the air.

Uses of static electricity: air fresheners

Uses of static electricity:
painting cars

Cars sometimes become
charged by friction
as they drive along.
Why doesn’t the charge
leak away to Earth?
How can this problem be solved?
During what type of weather
will you not receive a shock?

Once landed, why must a plane
be safely discharged
(known as earthing)
before it is refueled?

Van de Graaff generator

Both objects are now equally charged,
with opposite charges
because electrons have moved.

Charging by friction

The wool and polythene
are each ‘uncharged’.
What does this mean?

Factories use static electricity to reduce pollution coming from their smokestacks. They give the smoke an electric charge. When it passes by an electrode of the opposite charge, most of the smoke particles cling to the electrode. This keeps the pollution from going out into the atmosphere.

Uses of static electricity: smokestacks

What happens if you do not discharge yourself through a resistor?

The dome has a negative
charge (it has gained electrons),
so anything and anybody
connected to it has
a negative charge.

His hair stands up
because the negatively–charged hairs repel each other.

This Van de Graaff
generator builds up
a negative charge
on the dome.

Explain why his hair is standing up
How can this
negatively-charged balloon stick to an uncharged wall?

What are the electrons doing?
This is similar to which other topic in Physics?

Objects which have the same charge _______ each other.
Objects which have opposite charges _______ each other.
Charged objects always _______ uncharged objects.


Rub a plastic ruler with the duster and balance
it on an evaporating dish so that it is still.
Rub a second plastic ruler with the duster
and put the two rubbed ends near one another.

Can you think of an everyday example
where you can get charged by friction?

Insulating materials can be charged by rubbing.
There are two types of charge:
positive and negative.

This leaves a positively-charged surface
which attracts the negatively-charged balloon.

The electrons in the balloon
repel the electrons
in the wall a little deeper into the wall.

How can this negatively-charged balloon
stick to an uncharged wall?

The wool is ‘uncharged’, because…

By giving the paint an electrical charge, when it is sprayed on in a fine mist, the charged paint particles are attracted to the car or bike and stick to the body.
Once the paint dries, it sticks much better to the car or bike and is smoother because it is evenly distributed.

What happens.
Your explanation for why this happens.
1. Describe and explain what would happen if you brought the rod near an A4 piece of paper.
2. If a metal rod was rubbed in the same way, what difference, if any, would you expect to notice? Explain why.
…it has equal amounts of positive and negative charge.

Copy & complete:
Write down in your exercise book:
What happens.
Your explanation for why this happens.
Why the same thing would not happen
if a metal rod was used instead.
Extension task:
See what happens when you rub the plastic ruler with a duster and hold it near a small stream of water from a tap (do not get it wet!)
(and don’t just say “it’s because of static electricity”)
Explain why his hair is standing up
How does a photocopier work?
Uses & Problems

2.21 recall that insulating materials can be charged by friction
2.22 explain that positive and negative electrostatic charges are produced on materials by the loss and gain of electrons
2.23 recall that there are forces of attraction between unlike charges and
forces of repulsion between like charges
2.24 explain electrostatic phenomena in terms of the movement of electrons
2.25 recall the potential dangers of electrostatic charges,
eg when fuelling aircraft and tankers
2.26 recall some uses of electrostatic charges,
eg in photocopiers and inkjet printers.

Don't let it touch the table!
The gold leaf electroscope
is an instrument for detecting charge.
Draw the diagram in the textbook page 69 and write a brief description of how it can be used to detect electric charge.
Write your own brief notes (summarise, don't copy!)
on the three uses of static electricity described in the textbook.
Print and include diagrams for each.

Electrostatic paint spraying
Inkjet printers
Electrostatic precipitators
Aircraft may become charged as they fly through the air, as may fuel tankers as they drive along roads over long distances.

This build up in charge results in a large potential difference, which may lead to spark escaping to earth. This is spark occurs during a transferal of fuel, it could cause an explosion.
Dangers of static electricity
Why do electrical items, like your TV screen,
get dusty really quickly?
Television screens and computer monitors become charged with static electricity as they are used.
These charges attract light uncharged particles.
To put it simply: they get dusty.
Our clothing can become charged with static electricity and removing clothes can result in a small electric shock as the charges escape to earth.
Page 73 of the textbook
question 1 part d & e
question 2 b & c
question 3
question 4
Page 90 of the textbook
question 5
Full transcript