P4 Flashcards
What happens when two insulating materials are rubbed against one another
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 becomes negatively charged.
The material that loses electrons is left with an equal positive charge
What happens when two electrically charged objects are brought close to one another
When two electrically charged objects are brought close together they exert a force on each other. Two objects that carry the same type of charge repel.
Two objects that carry different types of charge attract.
Attraction and repulsion between two charged objects are examples of non-contact force
When two insulators are rubbed together what decides where the electrons transfer from
It depends on the materials involved e.g polythene and acetate rods being rubbed with a cloth duster
How do sparks occur from static electricity
The potential difference between the object and earth changes when an electric charge builds on an object
If this gets large enough, electrons can jump between the charged onject and an earthed object causing a spark
What does a charged object create and how does it change
A charged object creates an electric field around itself.
The electric field is strongest close to the charged object.
The further away from the charged object, the weaker the field
What happens when another charged object is placed in the electric field
A second charged object placed in the field experiences a force.
This is caused by by the electric fields of the objects interacting with eachother
The force gets stronger as the distance between the objects decreases
What is electrostatic attraction/ repulsion and how can it be tested
Objects lf the same charge will repel and objects of a different charge will attract, these forces get weaker the further apart the objects are
These forces will cause the objects to move ( electrostatic attraction/ repulsion )
A way to test this is hanging a rod with a known charge from a piece of string and placing an object with the same charge nearby to repel the rod. This will cause the hanging rod either to move away or towards the this depending on it’s known charge
How can you show an electric field around an object
Field lines
Field lines always go from positive to negative
They are always at a right angle to the surface
The closer you go to the field the stronger it is amd the further you go the weaker it is. This can be seen from the field lines getting closer together and further away from each other s the distance changes from the object
How do electric fields explain sparking
The high potential difference between the charged object and earth causes a strong electric field between the charged object and and the earthed object
This field causes electrons in the air particles to be removed ( ionisation )
The ionised air turns from an insulator to a conductor so a current can flow through it
This is the spark
