4.6.3 Magnetism and Electromagnetism Flashcards
What do we call the two ends of a magnet?
north pole and south pole
Two magnets are next to each other. They are arranged with ‘unlike’ poles next to each other
North-South North-South
What happens to these magnets?
They attract together as opposite poles attract
Two magnets repel each other. How are they arranged?
North-South South-North
Or
South-North North-South
With ‘like’ poles next to each other
Is the magnetic force between two magnets a contact or a non contact force?
Non contact - the magnets don’t need to be touching to exert a force on each other
What is an ‘induced magnet’?
It is a material that becomes magnetic when placed in a magnetic field.
What are the four magnetic materials?
Iron, Steel, Cobalt, Nickel
What is a ‘magnetic field’?
The region around a magnet where a force acts on other magnets or magnetic materials
Where is the magnetic field strongest around a magnet?
At the poles
Which direction does a magnetic field line go?
From north pole to south pole
How does a compass work?
A compass has a small magnet in it. It’s needle points in the direction of the Earth’s magnetic field.
What causes the Earth’s magnetic field?
Movements in the liquid, iron-rich part of the
outer core of the Earth.
Is the Earth’s magnetic field constant?
No, it has reversed it’s direction in the past (the last time was 800,000 years ago).
What is the ‘right hand grip’ rule?
When an electrical wire has a current flowing through it, it creates a magnetic field. The thumb shows the direction of the current, the circling of the fingers shows the direction of the magnetic field.
What is the shape of the magnetic field around a wire?
It is in circles.
What is an electromagnet?
It is an iron core, wrapped in electrical wire. When a current is passed through the wire it creates a magnet. It must have an IRON core to be an electromagnet, not just a solenoid.
What is a solenoid?
It is a core, wrapped in electrical wire. When a current is passed through the wire it creates a magnetic field.
How can you increase the strength of an electromagnet?
Increase the current
Increase the number of turns of the wire
Increase the size of the iron core
HIGHER TIER ONLY:
Flemings left hand rule is used to predict the direction of the force on a conductor. Arrange your left hand! What does each part represent?
Your thumb, first finger and second finger should be at right angles!
ThuMb for the MOVEMENT (of the force)
First Finger for the magnetic FIELD direction
seCond finger for the CURRENT
What is the equation to calculate the force of the movement created by a magnetic field?
force = magnetic flux density x current x length
HIGHER TIER ONLY:
How does an electric motor work?
A simple electric motor is made of a rectangular
coil of wire that is free to turn in the magnetic
field of a permanent magnet. A commutator
reverses the direction of the current every half
turn, to allow the rotation to continue.
How can you find the magnetic field around a magnet?
Use a small plotting compass. Draw dots at the end of the needle.
Or
Cover the magnet with a piece of paper and shake iron filings over the top.
When a current is passed through a wire it creates a magnetic field. What happens if you reverse the direction of the current?
The magnetic field also reverses.
