Magnetism Flashcards
Permanent magnets
a magnet that retains its magnetism even after removal of magnitising force (such as steel)
hard magnetic materials
magnetic materials that can be permanently magnetised
examples of hard magnetic materials
alloys of iron, nickel and cobalt
soft magnetic material
magnetic materials that are only temporariliy magnetised
example of soft magnetic materia
iron
ferrous
a material that contains iron
electromagnet
consist of a coil of wire wrapped around a magnetically soft core and can be turned on and off with a current
methods of magnetisation
- Stroke the material with a magnet
- coil of wire with current flowing through (electromagnet)
- hammer them inside a magnetic field
methods of demagnetisation
- hitting it with a hammer
- heating them
- place an object inside a coil of wire with an alternating current and remove the object
the curie point
when an object loses it’s magnetisation (permanent)
what causes magnetism
Caused by moving charges
permanent magnet uses
Compasses, School lab experiments, toys, fridge magnets
electromagnet uses
MRI scanners - produces diagnostic images of organs
Speakers and earphones - use electromagnets to sense or send sound waves
Recyling - seperate metals from other materials
Mag-Lev trains - hovering reduces friection and allows extremely high speeds
magnetic materials
can repel and attract other magnetic materials
unmagnetised materials
only attract, not repulse
- a magnet can only repel another magnet
how to test if a material is a magnet
bring it close to a known magnet.
- if can be repelled then the material itself is a magnet
- if only attracted and not repelled, then it is a magnetic material
types of magnets
permanent magnets
induced magnets
how can a magnetic material be induced
when the magnetic material is placed in a magnetic field - the material can be a magnet temporarily
magnetic field
a region around a magnet where a force acts on another magnet or on a magnetic material
- all magnets are surrounded by this field
magnetic field lines
used to represent strength (shown in distance between lines) and direction (shown in arrows) of a magnetic field
- north to south
- must never touch or cross other field lines
magnets are strongest at the poles; the magnetic field lines are closest together
