Static Electricity Flashcards
What is the charge of an electron
1.6*10^-19 C
What two factors affect electric force between two point charges
Magnitude of charges or distance between charges
What is the conservation of electric charge
It states electric charge cannot be created or destroyed, only transferred from one object to another. The total charge of a system stays constant unless some charge enters or leaves the system
What is an electric field
Electric field is a region in which electric charge experiences an electric force
How to determine the direction of electric field
Direction of electric force on small positive charge
Charging by friction
Before rubbing, items are electrically neutral. During rubbing, some electrons from _ are removed from atoms and transferred to _. _ has excess of electrons and is negatively charged/Electrons transferred remain at surface where rubbing occurred. _has deficit of electrons and is positively charged
Why does fur lose electrons and not amber rod
Atoms of different elements have different characteristics and less tightly held electrons from fur are transferred from amber
Why do electrons remain at surface of rubbing
Electrons cannot move freely throughout insulator, electrons transferred cannot move elsewhere and vacant electron sites cannot be refilled by other electrons
How to generally describe charging
Free moving electrons flow where (attracted/repelled), as like/unlike charges attract/repel, leaving positive charges behind(if applicable), state charge of object
Charging by contact
FARPC
Charging by induction
FARPC, keeping charged rod in position, separate two objects to isolate two groups of opposite charges. Remove rod and now objects have equal number of excess opposite charges, they distribute themselves equally apart on surface of sphere
Charging single sphere by induction
FARP, without removing rod, earth object, flow of electron from earth neutralises excess positive charges on object. Remove finger and allow free moving electrons to redistribute themselves equally apart on the surface. C
Why are neutral insulators attracted to charged object?
Electrons in atoms/molecules are attracted/repelled by charged object. Movement of electrons allows unlike charges between_ and _ to be closer compared to like charges. Force of attraction greater than force of repulsion, so insulator attracted
How does heating discharge objects
Heating ionises air around charged object. Positive and negative ions around heating flames. If negatively charged, negative ions will be attracted to insulator to neutralise positive charges and vice versa.
How does humid environment discharge object
Moisture on surfaces of charged object and in the air can conduct and lead to loss of static charges.
How does earthing discharge objects
Earth easily accepts/gives up electrons. Reservoir for charge. Excess free moving electrons to flow away from conductor, electrons flow to conductor to neutralise excess positive charges.
Describe ignition of flammable substances as hazard of electrostatic charging
Electric charges may build up on trucks due to friction between road and rotating tires. Sudden discharge may cause sparks and ignite flammable items that truck may be carrying. Fuel tankers have metal chain at rear of vehicle which hangs close to ground and provides earthing path for excess charges
Describe hazards of electrostatic charging to electronics
Electrostatic discharge an damage electronic equipment such as circuit boards and hard drives. items are usually packed in antistatic packaging. Antistatic materials have thin layer of metallic film, acts as electrostatic shield for enclosed item
How to prevent damage from lightning
Lightning conductors protect tall buildings by providing conducting path for electrons to flow from top of tall building to the Earth. This prevents lightning from damaging the building.
How to use static electricity for spray painting
As spray of paint leaves nozzle of gun, paint particles are charged by friction. Since paint particles have like charges, they repel one another and spread out when they leave the nozzle. Charged paint particles attracted to metallic car body, which is earthed and produces uniform coat of paint
How does electrostatic precipitator work
Unwanted particles become negatively charged by free electrons and negative ions generated by negatively charged wires. Negatively charged particles are attracted to positively charged plates and collected
