Magnetism Flashcards
Ferromagnetic alloys and compounds
Are magnetic
Eg iron, nickel, gadolinium or other ferromagnetic alloys or compounds
Law of magnetism
The law of magnetism states that like poles repel each other and unlike poles attract each other
Proving that something is a magnet
Only repulsion between a specimen and a magnet allows us to conclude that the specimen is a magnet
Direction of magnetic field lines
Outside the magnet, arrows point from North to South
Inside the magnet, arrows point from South to North
Needle of compass points…
South. Geographic north is actually true south
When is something magnetized?
When the magnetic domains in a ferromagnetic materials are aligned in the same direction, it becomes magnetized
How are ferromagnetic materials classified?
Soft magnetic materials and hard magnetic materials
Soft magnetic material
A material that is easily magnetized and demagnetized
Hard magnetic material
A material that is difficult to demagnetize
Aka permanent magnetic material
Magnetic induction
In the presence of a magnet, an object made from ferromagnetic materials will itself become a magnet
The magnet attracts the object because the pole of the magnet closes to the object produces an unlike pole in the nearest part of the object
When a magnet is cut into 2 or more pieces, each piece becomes a new magnet
Methods of magnetization
To magnetize an object is to align the magnetic domains within the object itself
1) stroking with a permanent magnet
2) electrical method- place a steel rod in a solenoid and connect the solenoid to a D.C. Supply. This method is most effective in producing a powerful magnet
Methods of demagnetization
To demagnetize a magnet is to disturb the alignment of the magnetic domains so that they all point in different directions
1) hitting the magnet with a hammer
2) putting the magnet over intense heat
3) electrical method- place the magnet in a solenoid and connect the solenoid to an AC supply. Remove magnet slowly in east-west direction
Define magnetic field
A magnetic field is a region where a magnetic material will experience a force
Density of magnetic field
The field strength decreases with increasing distance from the poles
Magnetic screening
Magnetic field lines cannot be destroyed or absorbed but they may be channeled away to protect a specific region; materials which do this are themselves magnetic
