SP11: static electricity Flashcards
how do objects get charged?
-when insulating materials rub against each other, they may become electrically charged
-electrons, may be ‘rubbed off’ one material and on to the other
-the material that gains electrons becomes negatively charged
-the material that loses electrons is left with a positive charge
what happens when a plastic rod with negative charges & duster with positive charges rub together?
- the duster is rubbed back and forth along the plastic rod
- the plastic rod transfers its electrons to the duster which is now negatively charged while the rod is positively charged
(friction causes electrons to gain enough energy to leave the atom and ‘rub off’ onto the rod)
what type of materials does static build up on and why?
-insulators
-insulators prevent the electrons from moving and the charge remains static
-conductors, cannot become charged, as the electrons can move through them
how to earth something?
connect a static charge to earth using a conductor, this will remove the excess charge as electrons will move to cancel out the charge
if a cloth rubs a plastic rod and the cloth is pulled away from the rod slightly, will the rod and cloth attract, repel or experience no force at all?
-the rod and cloth will attract
-this is true as long as there is enough friction to transfer electrons
how do insecticides use static charge?
-insecticide sprays can be electrostatically charged so that they cover a large area
-the droplets of insecticide are all given the same static charge as they leave the spray nozzle
-the static drops spread evenly as they all have the same charge and repel each other
-they are also attracted to the earth, so will fall quickly and are less likely to blow away
advantages of insecticides
less spray is needed
how do photocopiers use static charge?
photocopiers also use static electricity to attract the small particles of ink onto the paper in the right places
the electrostatic precipitatator
to clean small particles from smoke before it leaves an industrial chimney, a machine called an electrostatic precipitator will use static electricity to attract the particles
fuel & static
-fuel running through the pipes can provide the friction needed to create a static charge
-when the nozzle is put in the tank, static energy is gained from the car & charge builds up, causing sparks and fire
people & unexpected static
-sometimes a spark discharge may happen if a charged person touches an earthed conductor
-eg: a person dragging their feet across the carpet may become charged, if they then reach out to touch a door handle or another person, there is a spark and they feel a small shock
what is an electric field?
the area around a charged object where the object’s force is can act on other charged objects
van de graaff generator
a machine that causes friction between a rubber belt and plastic rollers to build up electrical charge on a metal dome
effects of a van de graff generator on a person
-a person does not have to touch the van de graaff generator to start feeling the effects, as static electricity is a non-contact force
-a person touching the dome of the van de graaff generator will lose electrons and become positively charged, the same will happen to each of their hairs
-since the person, their head, and each of the hair follicles are all positively charged, the hairs will repel from the head and from every other strand causing them to stick out from the head in all directions
electric field diagrams
-the direction of the arrow shows where a positive object would interact with the charged object (pos outwards, neg inwards)
-the closer together the lines are, the stronger the field and the greater the force experienced by charges in that field
-the field is stronger closer to the object.
