Topic 11: Static Electricity Flashcards
11.1P Explain how an insulator can be charged by friction, through the transfer of electrons
When insulating materials rub together, negatively charged electrons are transferred from one material to another.
The electrons, as the materials are insulators, are not free to move - so the build-up of charge is static electricity.
11.2P Explain how the material gaining electrons becomes negatively charged and the material losing electrons is left with an equal positive charge
The material gaining electrons ends up with a negative static charge.
The material losing electrons ends up with a equal positive static charge.
11.3P what happens with like and unlike charges
Like charges repel and unlike charges attract.
11.4P Explain common electrostatic phenomena in terms of movement of electrons, including
a shocks from everyday objects
As the electric charge builds up, the potential difference between the earth and the objects increases.
When the potential difference gets large enough, electrons are able to jump between the charged object and the earth.
Shocks from everyday objects have a small gap for the electrons to jump over.
11.4P Explain common electrostatic phenomena in terms of movement of electrons, including
b lightning
Shocks from everyday objects have a large gap for the electrons to jump over.
11.4P Explain common electrostatic phenomena in terms of movement of electrons, including
c attraction by induction such as a charged balloon attracted to a wall and a charged comb picking up small pieces of paper
Holding a negatively-charged balloon against a wall like cause it to stick to the wall.
As the negative charges of the balloon repel the negative charges on the surface of the wall, leaving positive charges on the wall.
Which will attract the negatively-charged balloon.
(attraction by induction)
11.5P Explain how earthing removes excess charge by movement of electrons
Earthing connects a charged objects to the earth using a conductor, providing a route for the static charges to travel to and from the ground.
- No static charge is able to build-up.
11.6P Explain some of the uses of electrostatic charges in everyday situations, including insecticide sprayers
When spraying crops with insecticide, electrodes on the spray nozzle charge the spray droplets as they pass. The charged droplets spread out because they repel each other and then they are attracted to the plants by induction. This means that the spray spreads around the plant, even underneath it.
11.7P Describe some of the dangers of sparking in everyday situations, including fuelling cars, and explain the use of earthing to prevent dangerous build-up of charge
Sparks can be dangerous, for example when there is fuel vapour that could ignite. This can be a problem for refuelling aircraft, which often became charged when flying through the air. A charge can also build up when fuel flows through a pipe and an aircraft, a ‘bonding line’ is connected to earth the aircraft before refuelling begins.
At petrol filling stations the storage tanks, pipes and hoses and earthed.
11.8P Define an electric field as the region where an electric charge experiences a force
An electric field is the region where an electric charge experiences a force.
11.9P Describe the shape and direction of the electric field around a point charge and between parallel plates and relate the strength of the field to the concentration of lines
Electric fields point in the direction a positive charge would go e.g. if it’s positive, it will go away from positive charges or if it’s negative it will go towards positive charges. In parallel plates fields are uniform. The closer together the lines are the stronger the magnetic field is that the further away they are the weaker the magnetic field is
11.10P Explain how the concept of an electric field helps to explain the phenomena of static electricity
Electrons sit on the field lines proving static electricity exists
