Topic 11 - Static electricity Flashcards
Static electricity is caused by
Friction between two objects, where negative electrons rub off onto one of the objects. Since the material is an insulator, the electrons cant move. This leads to a build up of static electricity. This means both objects involved become electrically charged.
Resulting charges on the materials involved in static electricity
Material that loses electrons has a positive static charge. Material that gains electrons has an equal negative static charge
Like charges
Repel
Opposite charges
Attract
Attraction by induction is
When a charged object is held close to an uncharged object, it repels the like charges on the uncharged object so that there is oppsoite charges near eachother to attract
Example of attraction by induction
Rubbing ballon against hair transfers electrons to balloon, leaving it negatively charged.
When put against uncharged wall, it repels the negative charges so that there is posiitve charges on the surface, so there is attraction.
Static shocks from everyday objects occur because
When an electric charge builds on an object, the potential difference between the object and earth/body increases.
This can lead to electrons jumping between the gap and creating a spark.
When there is only a small gap, this can lead to static shocks.
How does lightning occur
When clouds rub together, the potential difference becomes very large between the clouds and the earth, so there is a very large spark of electrons in the form of lightning
Earthing is
Connecting a charged object to the ground using a conductor
Earthing leads to
An easy route for static charges to move from the object to the ground, preventing a buildup and possible shocks or sparks
Movement of electrons in earthing
If object has a negative charge, then electrons flow from the object to the ground
If object has positive charge, then electrons flow from ground to object
Static electricity is used in
Photocopiers
Somke reduction in industrial chimneys
Electrostatic paint and insecticide sprayers
How do electrostatic paint and insecticide sprayers work
The sprayer is charged, so that the liquid bcoems charged
The individual particles repel eachother so that the spray is spread out and even
The object being painted has an opposite charge so that is attracts the paint
Dangers of static electricity
Fuelling cars
Static on airplanes
Lightning
How is static electricity dangerous in fuelling cars
Fuel flows out of iller pipe and static can build up, which could lead to a spark, lighting the fuel
How is static on airplanes dangrous
Friciton between air and plane leads to a build up of charge
This can lead to interference with communication equipment
An electric field is
an area created around any electrically charged object. If a secondary charged object is inside it, a force is exerted on both charges
The closer to an object creating an electric field,
The higher the force
Electric fields aroudn an object can be drawn with
field lines
Field lines rules
Always positive to negative
Always at right angle to surface
The higher concentration of lines, the stronger the field
Draw at least 8 field lines
How is static electricity explained by electric fields
Sparks occur when there is a high enough potential difference between a charged object and the earth. This causes a strong electric field between the charged and earthed object.
This causes ionisation, where elctrosn in the air particles are removed
This ionised air is conductive, so current flows through to create a spark
