Magnetism And Electromagnetism (T6) Flashcards
What are the main natural elements that are magnetic?
Iron, nickel and cobalt
Magnetism is a phenomenon resulting in…
Attractive or repulsive forces
Which of the natural magnetic elements shows the strongest magnetism?
Iron
What are the two main types of magnetic field?
Hard and soft
How are the atoms positioned in a magnet and why?
In a magnet, the atoms all face in roughly the same direction, so that their magnetism effectively ‘adds together’ to make one strong magnetic field
Describe magnetically hard materials..
Bar magnets are made of materials that keep their magnetism because once the atom’s magnetic fields are aligned they are ‘set’ in place and will remain facing the same way forever.
This type of material is known as magnetically hard material.
These materials do not become magnets easily, but once they are magnetised they remain that way indefinitely.
Describe magnetically soft material
A magnetically soft material is a material that allows its atomic magnets to align to an external magnetic field very easily. A lump of magnetically soft material placed in a magnetic field will instantly become a magnet itself, as all of its atoms will align to create a magnetic field that is in the same direction as the external one. However, as soon as the external field is turned off or removed, the atoms will no longer align together. They will revert to random orientations and their magnetic fields will cancel each other out. This will result in the material losing its magnetism. These material are attracted to either the North or South Pole of any magnet but you can’t make a permanent magnet out of them. They are frequently used in electromagnetism.
What are the rules of attraction?
Like poles repel, unlike poles attract
All magnets have a north and South Pole. What happens if you cut a bar magnet in half?
Both halves will have a North and South Pole again
What is a magnetic field?
A region within a magnetic material that will experience a force
How can we investigate magnetic fields using easy to come by materials?
By place info a piece of paper over a magnet or magnets and sprinkling iron fillings over it.
The iron fillings tend to align over what we call the magnetic field lines, so they show the field quite well.
The patterns that appear will show magnetic field lines but they don’t show the direction of the field.
When we draw them correctly we put arrows on them from North to South.
The field lines actually pass through the magnet so they are continuous unbroken loops.
When two North or South poles face each other, the lines curve away from a central point. What is this point called and what happens at it?
It is called a neutral point.
At that exact position the two magnetic fields are equal in strength but opposite in direction so they cancel each other out perfectly so there is no magnetic field at that point (and no magnetic field lines)
We draw magnetic fields using lines of force, or flux lines. What do these show us?
- the shape of the magnetic field
- the direction of the magnetic field; the field lines travel from North to South
- the strength of the magnetic field; the field lines are closest together where the magnetic field is strongest
Whenever an electric current flows through a conductor, it creates a magnetic field which we call an
Electromagnet
The strength of the field of an electromagnet depends on the amount of current, however in most cases the field will be weak. If you want to design something that uses a magnetic field, like an electric motor or an electromagnet, what three things can you do to make the field strong?
- use a coil of wire with many turns. Each loop or turn of the coil will generate its own magnetic field and those magnetic fields will add together to make a much stronger one
- deliver as much current as possible through the coil
- wrap the coil around a magnetically soft material, such as iron. This has the effect of keeping the field lines more tightly packed together, which in turn will make the field stronger
NOTE: the wire must be insulated!!
