Magnetism Flashcards
What are Magnetic Materials?
Magnetic Materials are materials which can be attracted to a magnet
Examples of Magnetic Materials
Iron, cobalt, nickel and their alloys
What are Non-Magnetic Materials?
Non-magnetic materials are not attracted by a magnet
Direction a suspended bar magnet will point in
A suspended bar magnet will always point in the North-South direction
Pole that points to the North is
North Seeking Pole
Pole that points to the South is
South Seeking Pole
True or false: The poles of the magnets are at the ends.
False. The distance between the
poles are about 5/6 th of the length of the magnet
What is the laws of magnetism
Like poles repel
Unlike poles attract
What is magnetic induction?
Magnetic induction is the process whereby an
object made of a magnetic material becomes a
magnet when it is near or in contact with a magnet.
What is the theory of magnetism?
States that if a bar magnet is cut up into 3 smaller pieces, each piece becomes a bar magnet, with N and S poles
What is a magnetic domain?
A magnetic domain consists of a group of atomic magnets pointing in the same direction
How does magnetisation occur?
The magnetic domains in an unmagnetised bar point in random directions. When a bar magnet is brought near the unmagnetised bar, the magnetic domains point in the same direction, producing magnetism. N and S poles of adjacent domains cancel each other out. The atomic magnets at both the ends are free. This produces N and S poles at the ends. The atomic magnets at the ends tend to fan out due to repulsion between the like poles.
Methods of magnetisation
- Stroking
- Electrical method using direct current
How to determine poles of a magnet (solenoid)
Use right hand grip rule
Fingers - direction of current flow
Thumb - direction of north pole
Purpose of demagnetisation
To cause magnetic domains to point in random directions
Demganetisation (heating)
When heated, the atoms of the magnet will vibrate vigorously and lose alignment. By letting the magnet cool in thge east-west direction, we can ensure that the domains do not realign
Demagnetisation (hammering)
Hammering the magnet in the east-west direction alters the alignment of magnetic domains and causes magnet to lose magnetism.
Last method of demagnetisation
Electrical method using an alternating current
What are magnetic fields?
Region in which a magnetic object, placed within the influence of a field, experiences a magnetic force
What is magnetic shielding?
Magnetic field lines from N pole pass through iron container instead of the air. Magnetic field lines exit from right side of iron container and enter S pole. This protects equipment that is placed within the container
What are magnetic keepers?
Magnets tend to become weaker after some time if not stored properly, due to free poles at ends of magnet repelling one another. Soft iron keepers ensure that magnetic domains remain aligned in same direction
Properties of soft magnetic materials
Easy to magnetise and demagnetise
Examples of soft magnetic materials
Iron
What are soft magnetic materials used to make?
Temporary magnets
