magnetism Flashcards
what do permanent magnets have
north and south pole
the closer the magnets get
the stronger the attraction or repulsion is
how to test if in a object is a permanent magnet
it must repel another permanent magnet
what is the magnetic field
an area around a magnet upon which magnetic forces act on other magnets
how can the magnetic field be represented
how can magnetic field lines be shown
by sprinkling iron fillings
what is a magnetic material
materials that become affected by magnetic forces when placed in a magnetic field
what are soft magnetic materials
easily magnetised - iron
what are hard magnetic materials
difficult magnetise
what is an electromagnetic
a coil wrapped around a soft iron core
what happens in an electromagnet
- when a current flows through
- this magnetises the core creating a magnetic effect from current and iron
- when the current turns off, the iron quickly demagnetises
what is induced magnetism
when a magnet is placed near a unmagnetised magnetic material there is a force of attraction
what is induced magnetism used for
to make permanent magnets by placing a hard magnetic field in a strong magnetic field such as a solenoid
what happens when a current flows through a wire
creates a magnetic field because of moving charge carriers
what does the magnetic field around a long straight current consist of
concentric circled
how can the magnetic field around a wire be shown
what is a solenoid
a long coil
what can be identified in a solenoid
if the coils turn clockwise it’s north
if anti it’s south
what does the magnetic field strength depend on
current
distance
surroundings
what is a ferromagnetic material
creates a magnetic dipole
how can the strength of a solenoid be increased
increasing number of turns
using a soft iron core
increasing the current
what are the differences between electromagnets and permanent
electro can be turned off and on, perm is always on
electro can be varied in strength, perm is constant
polarity of electro can be reversed whereas perm has a constant dipole
how can permanent magnetism be weakened
through impact and be heated above curie temperature
how to eliminate the problem of the wire getting to hot in electromagnets
by using superconducting coils which require low temp to function
what is the motor effect
when a current wire is placed in a magnetic field and experiences a force
in what direction is the force to the current and magnetic field
perpendicular
if the current is parallel to the magnetic field what happens
no force is experienced
if the current is … to the magnetic field then the force is at its …
- perpendicular
- maximum
why does the motor effect happen
as the magnetic field of the current interacts with the magnetic field of the permanent magnet
this creates a force on both wire and magnet
how can the direction of force be predicted
what is the strength of the motor effect force determined by
current
magnetic field
length
angle - greatest at 90 and 0 where parallel
how to determine magnitude of motor effect force
F=BIL
F stands for
motor effect force in newtons
B stands for
magnetic field strength in tesla (T)
I stands for
current in Amperes (A)
L stands for
length of wire perpendicular to field in Metres
