static electricity - topic 10 Flashcards
electrical conductor is
if electrical charges can easily move through through a material, such as in metals
electrical insulator is
if electrical charges cannot easily move through a material, such as plastics or rubbers
what happens when a polythene rod is being rubbed with a cloth duster
electrons move from duster to rod so rod becomes negatively charged and cloth has equal positive charge. This happens because friction causes electrons to be scraped off one and onto the other
acetate rod being rubbed with a cloth duster
electrons move from rod to duster. Rod becomes positively charged and cloth has an equal negative charge
opposite charges
attract
like charges
repel
attraction by induction
electrostatic attraction occurring between charged and uncharged object
if static negative charge is brought close to a neutral object
negative charges in neutral object are repelled by static charges. This creates a small positive charge on the surface of the uncharged surface which attracts the negative static charge and the two objects stick together
if static positive charge is brought close to a neutral object
negative charges in object are attracted to positive charge and move towards it. This creates a negative charge on the surface of the uncharged object, which attracts the positive static charge
rubbing balloon against your hair or clothes
transfers electrons to the balloon, leaving it with a negative charge. If you then hold balloon to a wall, negative charges on balloon repel negative charges on wall. This leaves a positive charge on the surface, which attracts the negatively charged balloon and they stick together
if you run a comb through your hair
electrons are transferred form hair to comb, making it negatively charged. It can then be used to pick up little pieces of uncharged paper. Holding it near the paper, causes induction in the paper, causing paper pieces to jump up and stick to comb
uses of static electricity in chimneys
sides of chimneys have positively charges plates, which attracts the negatively charged smoke particles. Particles stick to the plates instead of travelling out of the chimney and into astmosphere
why electrostatic sprayers are used to spray insecticide
so less is blown away by the wind and the insecticide sprays evenly above the crops, giving them an even coverage. this happens as the spray gun is charged so the droplets also gain a static charge and they repel each other which causes an even spray
how electrostatic sprayers are used to pain bikes
spray gun is charged, which charges the small drops of paint as they are sprayed out of the gun. The frame is given the opposite charge to the gun and so paint is attracted to bike frame
what is a spark
when potential difference gets large enough, electrons can jump across the gap between the charged object and earth.
how do you get a spark from opening a door
negative charge builds up on your body, due to friction between your shoes and floor as you walk. When you go to open the door that has a metal handle, electrons jump from you to metal causing a shock
how is lightning formed
when raindrops and bits of ice bump together inside storm clouds, friction between them causes the top of the cloud to become positively charged and the bottom negatively charged. This creates huge PD. Electrons usually travel within the cloud or between clouds, creating lightning across the sky. However , some sparks are larger enough that the electrons can travel between cloud and ground
dangers of static electricity
static electricity builds up on objects whether they are wanted or not. This can be dangerous if it leads to sparking.
earthing
dangerous sparks can be prevented by connecting a charged object to the ground using a conductor such as a copper wire
what does earthing provide the electrons
an easy route to travel between object and ground and this removes any excess charge that could give you a shock or a spark.
electron flow in grounding if static charge on object is negative
down the conductor to the ground
electron flow in grounding if static charge on object is positive
up the conducutor from the ground
what is an electric field
region where an electric charge experiences a force
where do electric field line point from positive charge
away
where do electric field line point from negative charge
towards it
closer together the lines in electric field ….
the stronger the field
field lines radiate out from where
out from the centre of the point charge
the closer to the charge you are and the closer the field lines……
the stronger the field
uniform field
field between parallel plates and it means it has the same strength everywhere
if field lines between charged objects point in same direction, field lines will
join up and objects are attracted to each other
what do electric fields help explain
electrostatice events
how electric fields help explain electrostatic events
when object becomes statically charged, it generates an electric field. This field interacts with the electric fields of nearby electrons in other objects. This interaction causes an attractive electrostatic force and objects move towards each other such as balloon and wall
what is the danger of sparking when refuelling vehicles
static charges can build up when refuelling vehicles which can be very dangerous and sparks can cause the fuel to ignite causing a fire or explosion
