Static Electricity Flashcards
What happens when 2 insulating materials are rubbed together? How?
When certain insulating materials are rubbed against each other they become electrically charged. Negatively charged electrons are rubbed off one material and on to the other. The material that gains electrons has a negative static charge. The material that loses electrons is left with an equal positive static charge.
What is an example of building up static?
Polythene and acetate rods being rubbed with a cloth duster. The polythene rod gains electrons but the acetate rod transfers electrons.
What happens when 2 electrically charged objects are brought close together?
When two electrically charged objects are brought close together they exert a force on each other.
What kind of forces are repulsion and attraction examples of?
Attraction and repulsion between two charged objects are examples of non-contact force.
What are positive and negative charges only ever produced by?
The movement of electrons.
What happens to the pd between an object and the earth when an electric charge builds on the object?
The pd between the earth(0V) and the object increases.
What can happen if the pd get large enough?
electrons can jump across the gap between the charged object and the earth - this is the spark. They can also jump to any earthed conductor that’s nearby (these usually happen when the gap is fairly small) - this why you can get static shocks when you get out the car –> a charge builds upon the cars metal frame and when you touch the car the charge travels through you to the earth.
How can you test electrostatic forces of attraction and repulsion?
If a plastic rod with a known charge is suspended from a piece of string (so it’s free to move) is brought near to another rod of the same charge, they will move apart as they repel each other. If a rod with the opposite charge is brought close to the suspended rod, they will pull together as they attract each other.
What is created around any electrically charged object?
An electric field. The closer you get to the object the stronger the field is.
How can you show the electric field around an object?
By drawing field lines.
Electric field lines go from the ______ charge to the _____ charge.
Electric field lines go from positive to negative.
How is a stronger/weaker field represented by the field lines?
The closer together the lines are the stronger the field is - the further from a charge you go the further apart the lines are hence the field is weaker the farther away from the charge you go.
What happens when a charged object is placed in an electric field?
It feels a force it’s either attracted or repelled. The force is caused by the electric fields of each object interacting with each other and gets stronger as the distance between the two objects decreases. The force on the object depends on the strength of the electric field it’s in.
How can sparks be explained by electric fields?
Sparks are caused when there is a high enough pd between a charged object and the earth/an earthed object. A high pd causes a strong electric field between the charged object and the earthed object which causes the air to be ionised (electrons removed). When ionised air becomes more conductive (is usually an insulator) so a current can flow through it - this is the spark.
