SP11 Flashcards
Why does an insulator not conduct electricity
The electrons are fixed so cannot flow
How is an insulator charged by friction
When two insulators are rubbed together it can be charged electrons are transferred from one object to another
This causes one insulator to be positively charged and the other to be negatively charged
Why does an insulator become positively or negatively charged
A positive static charge forms on the insulator that loses electrons
A negative static charge forms on the insulator that gains electrons
Which insulator loses/gains electrons is based on materials
Why can conductors conduct electricity
Their electrons can flow as they aren’t fixed because they are delocalised
What happens when conductors experience friction
If conductors are rubbed against each other, electrons will flow in/out and will cancel each other out keeping the conductors neutral
Like charges
repel
Opposite charges
attract
What are sparks
The spark is when the charge jumps through the air from the highly negative charge to a highly positively charged object, to balance out the charges
What is sparking
Sparking occurs when charge builds up and the objects are close but not touching
What is lightning
Lightning is caused when the charge between the clouds and the earth is so great that a massive spark jumps across the gap to balance the charge
What is an electro-static force
It is the force experienced by charged objects of either attraction or repulsion
How is charge related to the strength of electro-static forces
The greater the charge the greater the force (Positive/Negative)
The closer the charges the greater the force as the force is proportional to the inverse square law
As objects are not touching it is a non-contact force
How do charges relate to induction
A positively charged balloon next to the wall attracts the electrons in the wall as they are oppositely charged.
This induction causes the balloon to stick to the wall
A charged comb is able to pick up pieces of paper as it induces the opposite charge.
What is earthing
It is the removal of excess charge by providing a low resistance pathway for electrons to flow through
What does earthing accomplish
It allows materials to have a neutral charge
What are the applications of electro-static charges in everyday life
Insecticides are given a charge and sprayed
This charge causes them to repel each other and are spread evenly and are attracted to the earth
If they are not given a charge then some droplets will blow away or they will all spread unevenly
What are the dangers of sparking
If charge builds up and sparks while fuelling a car then an explosion can happen.
As fuel passes through a hose to the vehicle, a static charge can build up and when the charge is too big it can spark igniting the fuel
Hoses are earthed to avoid this
What is an electric field
A region in which a charge will experience a non-contact, electric force.
All charged objects have an electric field and this field is stronger the closer you are to it
They point in the direction a positive charge would go which means towards negatively charged objects
They point to charges at right angles to the surface
What are electric field lines
Lines representing an electric field, that point in the direction in which a positive charge would experience a force. The closer they are the stronger the field
What is a parallel plate
The electric field between two charged plates is uniform. The field lines are parallel, equally spaced and point from the positive plate to the negative plate
