Section 6 - Electric and Magnetic Fields Flashcards
What causes a build-up of static?
Friction
What happens when certain insulating materials rub?
They pass negativelt charged electrons from one to the other
Why are the electrons not free to move in insulating materials?
The materials are insulators
What do electrically charged objects do?
Exert a force on one another
What does too much static cause?
Sparks
Why does static electricity cause sparks?
There is a potential difference between the two which will eventually cause the electrons to flow
Jake removes his jumper in a dark room. As he does so, he hears a crackling noise and sees tiny sparks of light between his jumper and his shirt
Explain the cause of this
As the jumper rubs the shirt, a static charge is built up where electrons are removed from one and deposited on the other. The charge will eventually build uo where the charge is large enough to jump across the air gap causing sparks
What uses static electricity?
Photocopiers
Electrostatic sprayers
What type of charges are in insulators?
Fixed Charges
What type of charges are in conductors?
Mobile Charges
What is the difference between conduction and induction?
Conduction is direct contact
Induction is no contact
How does a negative balloon stick to a neutral wall?
The electrons move from the protons in the wall, causing the balloons electrons to be attracted to the protons
How do insecticide sprays work?
The gun is charged
Each drop is charged, so each drop repels eachother meaning the spray is fine and spread
Whats special about painting car and bikes?
The object sprayed is often the opposite charge to the spray so the spray attracts to the object
When can static electricity be dangerous?
Refueling cars
Static on airplanes
Lightning
How can refueling cars be dangerous?
As fuel enters the car the static can build up this can lead to a spark
How can static on airplanes be dangerous?
It can interfere with communication equipment
How do airplanes build up static?
As they fly through the air friction between the air and the plane causes the plane to become charged
How does lightning form?
Raindrops and ice bump together inside clouds, leaving the top positive and the bottom negative leading to a high voltage and a big spark
How can electrostatic charge be stopped?
By earthing an object
What is earthing?
Connecting a charged object to the ground using a conductor
What does earthing do?
Provide an easy route for the static charges to travel into the ground
How do electrons flow when earthing if the charge is negative?
Away (down)
How do electrons flow when earthing if the charge is positive?
Towards (up)
Give two uses of static electricity
Any two from: Photocopiers Reducing pollution Painting cars Electrostatic sprayers Insecticide
What do electric charges create?
An electric field
Where is an electric field created?
Around any electrically charged object
When drawing field lines, what direction are the lines drawn?
Positive to negative
When drawing field lines, what angle are the lines drawn at
90*
When drawing field lines, what do the distance between the lines resemble?
The strength of the field
How many lines must you draw when drawing an electric field?
8
Where is the strength and direction of the field different?
The end of the plates
What is an electric field?
The region where an electric charge
experiences a force
What is a magnetic field?
A region where other magnets or magnetic materials experience a force+
What direction do magnets always go?
North to south
What do magnetic fields cause?
Forces between magnets
How many lines should be drawn for a uniform magnetic field?
3
What does a compass needle always line up with?
The magnetic field it’s in
How do you build a picture of a magnetic field?
Put a magnet on a piece of paper and draw round it
Place the compass on the paper near the magnet, the direction of the magnet represents the field line at this position
Mark the position of the magnet and then move the compass so in the direction it points
Repeat this until you get several field lines
When do magnets not point to the north?
When they’re not near a magnet
Why do compasses work on the Earth?
The core is magnetic so it generates its own magnetic field
What are the three main magnetic elements
Iron, nickel and cobalt
Explain the difference between permanent and induced
magnets
Permanent magnets are always magnets whilst induced magnets are only magnets in the presence of an magnetic field
What can induced magnets not do?
Repel
What always happens between a magnet and a magnetic material?
Attraction
What are permanent magnets?
Magnets that produce their own magnetic field all the time
Explain how the behaviour of a magnetic compass is related to
evidence that the core of the Earth must be magnetic
Without another nearby existing magnetic field, a magnetic compass always points to the north of the Earth, suggesting the core of the Earth is magnetic
What are induced magnets?
Magnets that only produce a magnetic field while they’re in another magnetic field
What happens if you put magnetic material into a magnetic field?
It becomes an induced magnet
Why is magnetic induction always attractive?
Because the south pole of the magnet will induce a north pole in the material and vice versia