Topic 11 - Static Electricity Flashcards
How can an insulator become charged?
When they are rubbed together, friction causes electrons to be scraped off one and placed onto the other.
What is a static charge?
An electric charge that can not move.
They are found on electrical insulators where charge can not flow freely.
What charge is produced by gaining electrons
Negative
What charge is produced by losing electrons
Positive
What electrostatic forces happene between like and unlike charges
Like charges repel
Unlike charges attract
What is attraction by induction
Attraction between charged and uncharged objects
What are examples of attraction by induction
- Rubbing a balloon against clothes to transfer electrons to the balloon, creating a negative charge. The balloon will then repel the negative charges in the wall - leaving a positively charged surface for the balloon to be attracted to
- If you run a comb through your hair, electrons will transfer from your hair to the comb, making it negatively charged. It can then be used to pick up pieces of uncharged paper.
How does sparking work?
As electric charge builds up on an object, the potential difference between the object and an uncharged conductor (such as the earth) increases. If the potential difference gets large enough, electrons can jump across the gap.
How does lightning work?
It is a very large spark. Friction builds up within clouds causing a positive charge at the top and negative charge at the bottom of the cloud.
Electrons can travel between clouds, creating lightning across the sky, or electrons can travel between the cloud and ground, creating a lightning strike.
What is earthing
It involves connecting a charged object to the ground with a conductor (like a copper wire) to prevent sparks. Electrons travel from the object to the ground or vice verse - removing the excess charge needed to make a spark.
What are the benefits of electrostatic charge in insecticide sprayers
The insecticide spray spreads out evenly above the crops, giving them an even coverage. The insecticide also becomes attracted to the plants, due to attraction by induction, so less is blown away by wind.
What are the dangers of sparking involving refuelling cars
As fuel flows out of a filler pipe into a fuel tank, a static charge can build up on the fuel - causing a potential difference which can cause a spark and ignite the fuel.
What is an electric field
The region where an electrically charged object experiences a force
What are the main principles for drawing field lines
- Arrows go from positive to negative
- At least five lines at each point
- Weaker charge is found at lower frequency of lines
