4.2.5.1 Static Charge Flashcards
What happens when two insulating materials are rubbed against each other?
- both become electrically charged
- negatively charged electrons are rubbed off one material and on to the other - transfer of electrons caused by friction between the 2 materials
- the material that gains electron becomes negatively charged
- the material that loses electrons is left with an equal positive charge
When two electrically charged objects are brought closer together:
- they exert a non-contact force on each other
- two objects that carry the same type of charge repel
- two objects that carry different types of charge attract
- attraction and repulsion between two electrically charged objects are examples of non-contacts force
Electrical conductor:
a material that allows electrical charge to easily move through it
Electrical insulator:
a material does not allow electrical charge to easily move through it
What does friction lead to?
electron transfer
What do opposite charges do?
attract
What do like charges do?
repel
What do electrically charged objects exert on another electrically charged object?
exert a non-contact force
How to get rods to attract each other:
- bath rods must have different numbers of electrons
- can be achieved by friction
- electrons transfer from one rod to the other
How an uncharged object become positively charged:
Negatively charged electrons transfer from the neutral object by friction making it positively charged.
What type of charge is always transferred?
always negative charges (electrons) that transfer, never positive charges
Van de Graff Generator
- used to generate static electricity
- the longer the Van de Graff generator is switched on, the more charge is stored in the metal dome
- the amount of charge on the metal dome is increased, which causes the potential difference between the metal dome and. the earthed sphere to increase
Why does the rod attract the foil (rod has a negative electric charge and foil has a positive electric charge)?
The rod became charged when rubbed with a cloth due to friction causing negative electrons to transfer to the rod from the surface of the cloth. The excess electrons on the rod give it a negative charge.
Why does the rod move towards the foil (rod has a negative electric charge and foil has a positive electric charge)?
The foil sticks to a negatively charged cloth as when the rod is moved towards the foil the negative charges move to then end further away from the rod as they repel from the negatively charged rod. The side further away from the rod is negatively charged and the (opposite) side closer to the rod is positively charged. The positive side of the foil is attracted to the negatively charged rod.
What is the production of static electricity/sparks caused by?
- by rubbing surfaces which transfers negative charges (electrons) from one insulator to another
- this means they have equal opposite charges as electrons are transferred
- causes a build up of charge → creating a p.d. → sparks
Why is metal a good electric conductor?
- because electrons can flow easily through the metals
- they have free electrons
- unlike insulators
Why do objects like plastic not conduct electricity?
- they are insulators
- electrons cannot move through insulators
Why does a person’s hair stand up when they touch a Van de Graff generator?
- in the regenerator is a moving belt
- as the belt moves the electrons pass from the top plastic roller onto the belt
- electrons pass off the belt and are transferred to earth
- so over time the top region of the generator becomes charged
- the positive charge builds up on the metal dome
- if your are touching the dome you will also have a positive charge as the negative electrons are transferred to the generator to earth
- so the person Ould have an overall positive charge like the metal dome and as like charges repel the persons hair would stand up repelling from the metal dome
How can electric fields be used to explain why static charges create sparks.
- Stronger electric fields means some electrons are removed from the air
- causes air to become much more conductive meaning current can easily flow through it
- results in sparks
What is earthing?
- when the charge on an isolated object increases
- the p.d. between the object and the Earth increases
- path from high potential to 0V for charge to flow → creating a current
What does how close together the field lines show?
the closer together the field lines are the stronger the electric field
Why would a negatively charged person get an electric shock if they touched a metal object?
- there is p.d. between the student and the tap
- due to their p.d. the excess electrons transfer from the student to the metal tap which earths the charge
- electric current flows through the person giving them a shock
