Electrostatics Flashcards
what is a conductor
a material that allows charge to flow through it easily
what are some examples of a conductor
silver, copper, aluminium, steel, gold
what do conductors tend to be
metals
what are conductors made up of
positively charged metal ions with their outermost electrons delocalised. this means the electrons are free to move
why do metals conduct electricity very well
current is the rate of flow of electrons so the more easily electrons are able to flow, the better the conductor
what is an insulator
a material that has no free charges, hence does not allow the flow of charge through them very easily
what are some examples of insulators
rubber, plastic, glass, wood
although insulators are not very good at conducting, what else can they do
they conduct a little electricity in the form of static electricity. for example, two insulators can build up charge on their surfaces and if they touch this would allow that charge to be conducted away
what is the aim of the experiment for investigating charging by friction
to investigate how insulating materials can be charged by friction
what are the variables in investigating charging by friction
independent - rods of different material
dependent - charge on the rod
controls - time spent rubbing the rod, using the same type of cloth, using the same length of rod
what equipment is needed in investigating charging by friction
polythene rod, rods of different materials (perspex, acrylic, ebonite, glass, wood), cloths (one for each material), cradle, nylon string, and a wooden stand
what is the purpose of the polythene rod in investigating charging by friction
to charge and hang in a cradle to test against each material
what is the purpose of the rods made of different materials in investigating charging by friction
to charge and hold against the polythene rod to observe effects
what is the purpose of the cloths in investigating charging by friction
used to rub the materials to charge them
what is the purpose of the cradle in investigating charging by friction
used to support the rods to keep them horizontal
what is the purpose of the nylon string in investigating charging by friction
to hang the rods
what is the purpose of the wooden stand in investigating charging by friction
to attach the string and cradle to
what is the method in investigating charging by friction
1) take a polythene rod, hold it at its centre and rub both ends with a cloth
2) suspend the rod, without touching the ends, from a stand using a cradle and nylon thread
3) take a perspex rod and rub it with another cloth
4) without touching the ends of the perspex rod bring each end of the perspex rod up to, but without touching, each end of the polythene rod
5) record any observations
6) repeat for different materials
what happens when two insulating materials are rubbed together
electrons will pass from one insulator onto the other insulator
what charge is given to a polythene rod when rubbed by the cloth and why
a negative charge, and this happens because electrons move from the cloth to the rod. electrons are negatively charged hence the polythene rod becomes negatively charged
where do the electrons move when a polythene rod is rubbed by a cloth
to the rod
where do the electrons move when a acetate rod is rubbed by a cloth
to the cloth
what charge does the material have if the material is repelled from the polythene rod
the materials have the same charge
what charge does the material have if the material is attracted to the polythene rod
the materials have opposite charges
how could you improve the outcome of the experiment
consider investigating a variable with a numerical result. for example, the independent variable could stay the same (using rods of different material). the dependent variable could change to be the number of paper circles picked up by each rod
what is the advantage of having a numerical data outcome of an experiment
more analysis can be carried out e.g. creating a graph or a chart. better conclusions can be drawn e.g. the rod made of ___ picked up more circles of paper than the other rods, therefore it became the most charged
what happens when certain insulating materials are rubbed against each other
they become electrically charged
what happens to the charge on the insulators, and give an example
it remains and cannot immediately flow away. one becomes positive and one becomes negative. an example of this is a plastic or polythene rod being charged by rubbing it with a cloth. both the rod and cloth are insulating materials
what are the different charges that a particle could be
positive, negative or neutral
give an example of a negative, neutral and positive particle
electron, neutron and proton
when an object gains electrons, what charge does it now possess
negative charge
when an object loses electrons, what charge does it now possess
positive
what happens when two charged particles are close together
they exert a force on each other
what are the two possible forces that could come from moving two charged particles close together
attractive (the objects get closer together), or repulsive (the objects move further apart)
what decides whether two objects attract or repel
their charge
what force will be exerted on two objects with opposite charges
they will attract
what force will be exerted on two objects with same charges
they will repel
what charge to objects have initially
they are electrically neutral, meaning the negative (electrons) and positive charges are evenly distributed
what happens when electrons are transferred through friction
one object becomes negatively charged and one object becomes positively charged. the object to which the electrons are transferred to becomes negatively charged. the object from which the electrons leave from becomes positively charged
what does the difference in charges lead to
a force of attraction between two objects
what are two uses of static electricity
photocopiers, and insecticide
how do photocopiers use static electricity
to copy documents, mostly in black and white
explain how a photocopier uses static electricity to copy paper documents
an image of the document is projected onto a positively charged copying plate. the plate loses its charge in the light areas and keeps the positive charge in the dark areas (i.e the text). a negatively charged black toner powder is applied to the plate and sticks to the part where there is a positive charge. the toner is then transferred onto a new blank sheet of white paper. the paper is heated to make sure the powder sticks (hence why photocopied paper feels warm). the photocopy of the document is now made
how do inkjet printers work in a similar way to photocopiers
instead of the black toner powder, a small jet of coloured ink is negatively charged and attracted to the correct place on the page
how must insecticide sprayers spray crops effectively whilst using a minimal amount of chemicals
the sprayer has to deliver the chemicals as a fine mist and cover a large area
how does an insecticide sprayer deliver the chemicals as a fine mist and cover a large area
the insecticide is given an electrostatic charge (e.g. positive) as it leaves the sprayer. the droplets of insecticide then repel each other since they are the same charge. this ensures that the spray remains fine and covers a large area
what is the advantage of the insecticide being attracted to the negative charges on earth
they will fall quickly and are less likely to be blown away
what are some situations where static electricity can pose a hazard
the risk of electrocution (e.g from lightning). the risk of a fire or explosion due to a spark close to a flammable gas or liquid
what is used to prevent the build-up of charge
earthing, and is done by connecting vehicles to the earth with a conductor
how is the build-up of static charge a potential danger when refuelling aeroplanes
fuel runs through pipes at a fast rate. this fuel is very flammable. the friction between the fuel (a liquid insulator) and the pipe causes the fuel to gain charge. if this charge were to cause a spark, the fuel could ignite and cause an explosion
how is the build-up of static charge when refuelling aeroplanes prevented
the fuel tank being connected to the earth with a copper wire called the bonding line during the refuelling. the conductor earths the plane by carrying the charge through to the earth which removes the risk of any sparks
