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immagine (immagine (OERSTED'S EXPERIMENT immagine immagine = aā¦
POLES
MAGNETIC
āØ iron filing's effect : shows that force comes from 2 points
š Earth's effect : shows that there is a north-seeking pole and a south-seeking pole
ā¬ ā¬ 2 bar's effect : like poles attract and unlike poles repel (distance affect it)
GEOGRAPHICAL
HIPOTHESIS:
1) noth-seeking pole will point the geographical north
2) like poles attract and unlike poles repel
THESIS:
š's molten core has a MAGNETIC south pole near the GEOGRAPHICAL north pole
(sometimes is wrongly called magnetic north pole anyways)
INDUCED MAGNETISM
iron and steel put near a magnet
it induces magnetism in them
opposite poles = attraction
when pulled away from the magnet
steel ā keeps magnetism ā permanent magnet
iron ā loses magnetism ā temporary magnet
MATERIALS
MAGNETIC MATERIAL: magnetizable and attracted to magnets, contains iron/nickel/cobalt
HARD (steel) ā difficult to magnetize but difficult to demagnetize
SOFT (iron, Mumetal) ā easy to magnetize and easy to demagnetize = temporary magnet
! used in electromagnets and trasformers because they can be sweeitched on and off
FERROMAGNETIC MATERIAL: strongly magnetic
NON-MAGNETIC MATERIAL : brass, copper, zinc, alluminium
MAGNETIC FIELD PATTERNS
compass used to plot the field /more lines depending on position) around a bar, marking 2 dots and moving it
OERSTED'S EXPERIMENT
= a current flowing through a wire deflects a compass needle
ā electric current generates a magnetic field in concentric loops
"current-magnet interaction"
ELECTROMAGNET
can be switched on and off
core (iron/mumetal) + turns of coil (insulated copper wire)
when current ā magnetic field
.+ if + I
.+ if + turns
reverse I = reverse direction of m.f.
RELAY
= switch actioned by an electromagnet
small switch and thin wires to activate a poweful circuit
when current in the imput circuit ā iron armature attracted ā contact closes ā current flows in the output circuit
CURCUIT BREAKER
= automatic switch that cuts off current in a circuit when too high
ā fuse but can be reset = switched on again
when current too high ā electromagnet releases iron catch ā contact is opened
no current ā compasses point N
[ Earth's magnetic field = 0,5 Gauss]
current ā compasses align to magnetic field
[ Small bar magnet = 100 Gauss ]
BIOT-SAVART LAW
magnetic field lines are in loop
field strongest near wire
+(stronger) I = + field
SOLENOID
= long coil
produces stronger magnetic field
than a single turn of wire
FARADAY'S EXPERIMENT
= current flowing in a copper wire will move upwards or downwards (depending on his direction) because of the magnetic field created by a magnet
.+ m.f. if + I / + magnet / + lenght wire
"magnet-currrent interaction"
AMPERE'S EXPERIMENT
= 2 wires traversed by current generate magnetic fields that interact
"current-current interaction"
FARADAY + HENRI
magnetic field can produce electric current
AMPERE'S LAW
