Topic 1 - Static and Current Electricity Flashcards
What is contained in the nucleus of an atom?
Protons and neutrons
What is the overall charge of a nucleus?
Positive
What gives an atom its overall size?
Electrons whizzing around the outside
What is the relative mass of a proton?
1
What is the relative charge of a proton?
+1
What is the relative mass of a neutron?
1
What is the relative charge of a neutron?
0
What is the relative mass of an electron?
1/2000
What is the relative charge of an electron?
-1
What causes the build up of static electicity?
- When 2 insulating materials rubbed together, electrons are transferred from one to the other
- Positive static charge on one and negative charge on other
- Only electrons move, not protons
- Charges are equal + opposite
What happens when a polythene rod and a cloth are rubbed together?
- Electrons move from the cloth to the rod
- Rod becomes negatively charged + cloth has equal positive charge
What happens when an acetate rod and a cloth are rubbed together?
- Electrons transfer from the rod to cloth
- Cloth ahs negative charge + rod has equal positive charge
What happens when two objects have the same charge?
- Repel from each other as same charges repel
- Electrostatic forces of attraction
What happens when two objects the different charges?
- Attract together as opposite charges attract
- Electrostatic forces of attraction
How does static electricity cause clothes to crackle?
- When synthetic clothes dragged over each other (e.g. in tumble drier), electrons transfer, leaving static charges on both
- Attraction between items + little spark as charges rearrange themselves
How does static electricity cause car shocks?
- Static charge builds up between clothes + synthetic car seat; friction causes electrons to transfer
- When get out of car + touch metal door, charge flows giving a shock
- Some cars have conducting strips that hang behind car giving a safe discharge to earth
How does static electricity cause shocks from door handles?
- Walk on nylon carpet wearing shoes w/ insulating soles
- Electrons transfer from carpet to you so charge build up on body
- If touch metal door handle, charge flows to conductor giving a shock
How can a balloon be made to stick to a wall?
- Rub balloon against hair/clothes, so electrons transfer to balloon (giving it a negative charge)
- Sticks to wall although wall isn’t charged
- Charge on surface of wall moves a bit: negative charge repels so positive charge is on wall surface, attracting balloon, holding balloon to wall
- This is called induction
How can a comb be charged to pick up small pieces of paper?
- Run comb through hair, so electrons transfer to comb so it’s negatively charged
- Picks up paper although paper has no charge
- Negative repels so positive on top sticking to comb
- Induction
What causes lightning?
- Static charge
- Rain drops + ice rub together inside storm clouds
- Electrons transfer
- Positive charged on top and negatively charged on bottom
- Creates a voltage + spark as wants to get earthed
How do paint sprayers use electrostatic charges to get an even coat on bikes and cars?
- Spray gun charged, charging small drops of paint
- Drops repel others as same charge, so get fine spray
- Object given opposite charge to gun, attracting fine spray of paint
- Method gives even coat + hardly any paint wasted
- Parts facing away from the gun still get painted; no shadows
- Same as how insecticides sprayers work
How are electrostatic charges problematic when fuel filling and how can this be resolved?
- As fuel flows out filler pipe, static builds up
- Can easily lead to spark which can cause explosion
- Sparks prevented by being earthed
How does earthing stop electrostatic charges building up?
- Dangerous sparks can be prevented by connected charged object to ground by conductor (earthing)
- Provides easy route for static charges to travel into ground so no charge can build up to shock or spark
- Electrons flow down conductor to ground if charge negative + flow up conductor from ground if charge positive
Why must fuel tankers be earthed?
To prevent any sparks that might cause the fuel to explode
