P4a Flashcards
(16 cards)
What happens when some materials are rubbed together?
They attract other objects. Certain types of dusting brushes become charged and attract dust as they pass over it.
What happens when an insulating material is rubbed with another insulating material?
Electrons will be scraped off one and dumped on the other.
They become charged.
Which way the electrons are transferred depends on the two materials involved.
Electrically charged objects attract small neutral objects placed near them.
The classic examples are polythene and acetate rods being rubbed with a cloth duster. With the polythene rod, electrons move from the duster to the rod. with the acetate rod, electrons move from the rod to the duster.
What two kinds of charges are there?
Positive and negative.
Which charges repel and which attract?
Two things with opposite electric charges are attracted to each other. Two things with the same electric charge will repel each other.
What is electrostatic phenomena caused by?
The transfer of electrons, which have a negative charge.
Both positive and negative electrostatic charges are only ever produced by the movement of electrons. The positive charges do not move. A positive static charge is always caused by electrons moving away elsewhere. If enough static charge builds up, it can suddenly move which can cause sparks or shocks.
What is static electricity in terms of the movement of electrons?
A positive static charge is due to a lack of electrons - it lost electrons, so this leaves it positively charged.
A negative static charge is due to an excess of electrons - it gained electrons.
What are atoms or molecules that have become charged?
Ions
How can you get an electrostatic shock from synthetic clothing?
When synthetic clothes are dragged over each other, electrons got scraped off, leaving static charges on both parts, and that leads to attraction (they stick together and cling to you) and little sparks or shocks as the charges rearrange themselves.
How can you get an electrostatic shock if you become charged and then earthed from touching a water pipe,/metal door handle after walking on a nylon carpet?
If you walk on a nylon carpet wearing shoes with insulating soles, charge builds up on your body. Then if you touch a metal door handle or water pipe, the charge flows via the conductor and you get a shock.
How can electrostatic electricity be dangerous?
Static charges are a big problem in places where sparks could ignite inflammable gases or vapours, or where there are high concentrations of oxygen - there could be an explosion.
Also when large quantities of charge could flow through the body to earth.
How can grain chutes, paper rollers and fuel filler pipes be dangerous?
As fuel flows out of a filler pipe, or paper drags over rollers, or grain shoots, then static can build up. This can easily lead to a spark and might cause an explosion in dusty or fumey places - like when filling up a car with fuel at a petrol station.
How can static electricity be a nuisance when dirt and dust are attracted to insulators?
Dust particles are charged and will be attracted to anything with the opposite charge. Unfortunately, many objects around the home are made out of insulators (e.g. plastic containers, TV monitors) that get easily charged and attract the dust particles.
How can the chance of an electric shock be reduced by correct earthing?
Dangerous sparks can be prevented by connecting a charged object to the ground using a conductor (e.g. a copper wire) - this is called earthing and it provides an easy route for the static charges to travel into the ground. This means no charge can build up to give you a shock or make a spark.
How can the chance of receiving an electric shock be reduced by insulating mats?
Insulating mats and shoes with insulating soles prevent static electricity from moving through them, so they stop you from getting a shock.
How can the chance of receiving an electric shock be reduced by bonding fuel tanker to aircraft?
Fuel tankers must be earthed to prevent any sparks that might cause the fuel to explode - refuelling aircraft are bonded to their fuel tankers using an earthing cable to prevent sparks.
How do anti-static sprays, liquids and cloths help reduce the problems of static electricity?
Anti-static sprays and liquids work by making the surface of charged object conductive - this provides an easy path for the charges to move away and not cause a problem.
Anti-static cloths are conductive, so they can carry charge away from objects they’re used to wipe.
