7 - Static Electricity Flashcards
How does Static Electricity happen?
The build up of an electrical charge on any object, caused by friction
How do Insulators cause Static Electricity?
- When insulating materials are rubbed together, negatively charged electrons get scraped off one & dumped on the other
- The electrons aren’t free to move in insulators, building up the static electricity charge
What is the charge of a material that has lost electrons?
Positive
What is the charge of a material that has gained electrons?
Negative
Like charges _____ and unlike charges _____
repel
attract
What is attraction by induction?
When a positive charge on the surface of one object attracts another, negatively charged object
How can a balloon stick to a wall?
Rubbing a cloth on it - transfers electrons to the balloon, leaving a negative charge
The charges on the wall’s surface can move - balloon’s charge repels the negative wall charges away
How can a comb pick up paper?
Electrons are transferred to the comb as you run it through your hair, giving it anegative charge
Holding it near little, uncharged paper cause induction in the paper, making it jump up & stick to comb
What are some ways SE is used in Industry?
- Photocopiers
- Reducing dust & smoke from industrial chimneys
- Electrostatic Sprayers (give a fine even coat to whatever is sprayed)
As How do sparks occur?
As an electric charge builds on an object, the PD between Earth & object increases
If the PD gets large enough, electrons can jump across the gap between the charged object & Earth - a spark
How does lightning happen?
- Rain & ice inside clouds bump into each other, making the top of the cloud positively charged & the bottom negative
- Large PD is made as the charge builds up
- Sparks are created as electrons jump across gaps either in the cloud or to the ground
How can static on airplanes be dangerous?
Friction between the air & plane builds up & causes the plane to become charged
This can interfere with communication equiptment
How can static be dangerous when refuelling cars?
As fuel flows out of a filler pipe static can build up
This can cause a spark which may cause an explosion
What is Earthing?
Preventing sparks by connecting a charged object ot the ground using a conductor
How can Earthing prevent static charges being built up?
It provides an easy route for charges to go into the ground - electrons flow down the conductor if negative and flow up from the ground if positive
