uses of static electricity - · pdf fileaim •identify dangers in refueling and state how...

Uses of static electricity Book page 70 - 72

Syllabus 2.24 – 2.25 ©cgrahamphysics.com 2016

Starter

• Where is static electricity used?

©cgrahamphysics.com 2016

Starter

• Can you draw a sketch to explain how you can make a balloon attract your hair?


Aim

• Identify dangers in refueling and state how the problem can be avoided

• Recall some uses of static electricity

Key words

• Sparks - photocopier

• Paint spraying - inkjet printer

• Smoke precipitators


Have you ever wondered

The bigger picture

How can something as tiny as an electron cause an explosion?


Problems with static electricity • When a potential difference is created between two

insulators rubbed together, there is the risk of a spark developing

• Charging by friction causes the separation of negative and positive charges

• If the electrons find a connection, they can jump from one object to another, causing a spark

• The spark can cause a fire or explosion if it occurs near flammable material


Dangers of Static – fuelling lines • As aircrafts fly through the air,

they become charged by friction with the colliding air particles

• The potential difference between the plane and the earth increases

• When landed and refilling, it is possible for these charges to escape to the Earth

• To avoid risk: plane is earthed with a conductor as soon as it lands


Refuelling aircraft


Fuel tankers

• Fuel tankers are charged by friction in similar way while driving

• Filling a tank can also cause static charge build up as the fuel is rubbing the pipe and nozzle

• To avoid risk: tanks have conductors to provide earthing

• fuel nozzles have rubber shielding


Static electricity can be a nuisance! What causes the following annoying everyday incidents?

Electric shocks from

radiators in rooms with

nylon carpets.

Unruly hair after combing.

Dust collecting on TV

screens and computers.

Clothes clinging to the

body and to each other.


Van de Graaf generators

03/03/2016

When a charge is neutralised by the movement of electrons either from the Earth or to the Earth we call this “earthing”


Static electricity has many uses, including:

How can static electricity be used?

photocopiers

and laser

printers

filtering

factory

smoke

spray painting cars

heart

defibrillators


Using Static in Paint Sprayers

Connected to negative voltage

Connected to positive voltage

1) Why is the paint sprayer given a negative charge?

2) Why is the car given a positive charge? ©cgrahamphysics.com 2016

Uses of static electricity • Spray paint is charged negatively – the paint

droplets repel and will spread out as much as possible when released

• This will cause an even coat of paint

• The object to be painted is positively charged – this will attract the negative paint and allow and even coat in all areas, even those difficult to reach like tight corners


Inkjet printers • Each spot of ink is charged negatively

• The ink is released between two plates of opposite charge

• The ink will be attracted to the positive plate and change its path

• The charge on the plates will change and so direct the ink in different position, forming words and pictures


How does a photocopier work?


Photocopiers – writing with light • Positive charge is sprayed onto rotating drum coated with a the

metal selenium • A bright light shines on the paper to be copied • The white parts reflect light onto the drum, the dark parts do not • The selenium loses its charge where the reflected light hits the

drum • Where no light is reflected, the charge remains • The negatively charged toner is blown over the drum and sticks to

the parts that are still positively charged • A piece of paper is pressed against the drum and picks up the

pattern of the carbon powder • The carbon powder is fixed into place by a heater


Electrostatic precipitators

• Steel making furnaces and coal fired power plants produce smoke

• The smoke carries pollutants into the environment

• This causes health problems and damages buildings


Cutting down pollution • Smoke rises through a metal

mesh that is charged up to 50 000V

• Ash and dust particles become negatively charged as they pass through

• Higher up in chimney are positively charged metal plates, which attract the negative dust particles

• The cleaner smoke is now released into the atmosphere

• When the metal plates are completely covered with dust and ash, they are given a sharp rap

• The particles fall off into collection boxes 50 – 60 tones of dust and ash are removed every hour


Static electricity – useful or a problem?


What happens in a photocopier?


Plenary

• When two insulators rub together, what is transferred from one to the other?

A Protons

B Neutrons

C Electrons

D Volts


Question 2

• An insulator can gain a positive charge by

A Gaining protons

B Gaining electrons

C Losing protons

D Losing electrons


Question 3

• A negatively charged object can attract

A Another negatively charged object

B An uncharged object

C Any other object

D No other object


Question 4

• Electrostatic charge can be dangerous when putting fuel into an aircraft because

A Electrostatic fuel will make the airplane go too fast

B The aircraft will not be able to stop

C A spark can cause fire

D Electrostatic fuel will not burn properly


Question 5 • Electrostatic charge is used in spray painting a car by A charging the car positive or negative. It will attract the neutral paint. B charging the car positive and the paint negative. Opposites attract C charging both, the car and the paint, positive or negative. Opposite charge repel and the paint coating will be even D Spray paint the car and then apply are charge. This will cause the paint to be distributed evenly


Question 6 • Pollution from industrial chimneys can be reduced

by using

A taller chimneys

B thicker metal plates lining the chimney

C Black chimneys as they repel charged particles

D Charging the dust particles and attracting them to an oppositely charged metal plate in the chimney


Key words • Sparks – caused by a spontaneous discharge of

electrostatic charge • Paint spraying – uses opposite charges to spray an even

coat and an even layer in all places • Smoke precipitators – uses electrostatic charged dust

particles attracted to oppositely charged metal plates • Photocopier – uses reflected light and dark charged

areas to attract toner to image • Inkjet printer – uses charged ink and charged parallel

plates to create an image or words


uses of static electricity - · pdf fileaim •identify dangers in refueling and state how...

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