What is a build up of static caused by?
-by friction
1-electrons have a negative charge
2-two insulating layers rub together
3-electrons scrape off one and onto the other
4-leaving a positive static charge on the one that lost electrons and a negative charge on the one that gained electrons
-the way electrons are transferred depends on the two materials involved, e.g.polythene(gains electrons) and acetate(loses electrons) rod being rubbed with a cloth duster
How does static electricity attract dust?
- dust particles are charged and will be attracted to anything with opposite charge
- many things in the house are insulators so get easily charged and attract the dust particles
How does static electricity make clothing cling and crackle?
- dragging synthetic clothes over each other (dryer) or over you head, electrons are scraped off, leaving static charges on both parts
- and therefore leading to attraction, clinging clothes to you and sparks and shocks as the charges rearrange themselves
How does static electricity give you shocks from door handles?
- walking on a nylon carpet wearing shoes with insulating soles causes a charge to build in your body
- if you touch metal door handle charge flows through the conductor and you get a shock
How can static electricity building up in clothes be dangerous?
- lots of a static charge can build up on clothes made of synthetic materials, if they rub against other synthetic materials
- charge can become large enough to make a spark
How can filling planes with fuel be dangerous?
- when an aircraft takes on fuel, fuel rubs against the rubber tubes in the plane causing a charge
- if a spark is caused the plane will explode
- so a wire is connected to the plane and fuel take before hand
- this earths both of them and stops a spark from forming
Why are things insulated?
-insulating mats and shoes with insulating soles stop static electricity from moving through them and so they stop you from getting a shock
How do anti-static cloths work?
-conductive so they carry charge away from objects they’re used to wipe
How do anti-static sprays and liquids work?
- make the surface of a charged object conductive
- providing an easy path for charges to move away and not cause problems
How can dangerous sparks be prevented?
- by connecting a charged object to the ground using a conductor
- this is called earthing and provides and easy route for static charge to travel into the ground
- meaning no charge can build up and cause a shock or spark
How is static electricity used in spray paints?
-electrostatic paint sprayers used on bikes and cars
1-spray gun is charged, which charges up the small drops of paints
2-each drop of paint repels the others because they have the same charge (spray is very fine)
3-object being painted is given the opposite charge to the gun,
4-this attracts the fine spray of paint
5-this method gives and even coat and hardly any paint is wasted
6-parts of car or bicycle facing away from spray gun still receive paint (there are no shadows)
How is static electricity used in dust preciptators?
1-smoke particles reach bottom of chimney and meet a wire grid or rods with a high voltage and negative charge
2-dust particles gain electrons and become negatively charges
3-dust particles induce a charge on earthed metal plats (negatively charged dust particles repel electrons on the plate, so the plate becomes positively charged)
4-dust particles are attracted to metal plates, where they stick to form larger particles
5-when heavy enough, particles fall off plates or are knocked off by a hammer
6-dust falls to bottom of chimney and can be removed
-so gases coming out of the chimney contain fewer smoke particles
How is static electricity used in defibrillators?
-beating of heart is controlled by tiny electrical pulses inside your body, so an electric shock to a stopped heart can make it start beating again
-defibrillators used to shock a heart back into operation
-consists of two paddles connected to power supply
1-paddles placed firmly on chest of patient to get good electrical contact
2-defibrillators charged up
3-everyone moves away except operator who holds insulating handles (so only patient gets shock)
4-charge passes through paddles to the patient to make their heart contract
What do electrically charged objects attract?
-small neutral objects placed near them
Explain how it is only electrons that move in static electricity?
- charges do not move
- it is electrons that move to cause charges
What happens if enough a static charge builds up and what needs to be done about this?
- a big static charge can suddenly move and cause sparks or shocks that can be dangerous
- a charged conductor can be discharged safely by connecting it to earth with a metal strap
- this is earthing
- electrons flow down strap to ground if charge is negative and flow up strap from ground if charge is positive
Why are insulators easily charged?
-electrons in an insulator cannot more freely like electrons in a conductor, so it is easier for their electrons to be scarped off and dumped on something else
Where are static charges big problems?
- places where sparks can ignite inflammable gases
- places where there is a high concentration of oxygen (e.g. hospital operating theatre)
What are precipitators used for?
-to remove smoke (which is made of tiny particles) created by factories and power stations
