Magnetism/ electromagnetism Flashcards
any current….
makes a magnetic field
like poles…
repel
opposite poles…
attract
uniform field
- same strength at all points
- place two magnets near ( but not touching) with N facing S
- field lines are equidistant and parallel
straight wire magnetic field
makes a circular field
right hand grip rule
right hand grip rule
thumb = current
fingers = field
wire cross section - cross
current into page away from you
wire cross section - dot
current out of page towards you
soft magnetic material
easily magnetised/ demagnetised
eg IRON
hard magnetic material
remains magnetised
eg STEEL
magnetic material eg
iron
steel
nickel
colbalt
field flows
N>S
current flows
+>-
how to draw field shape
- place a plotting compass in the field
- note/draw direction
- move to new place and repeat
where is field strongest
where field lines are closest
how to make solenoid field stronger
- more current
- more coils/ turns in the wire
- add an iron core
moving charged particle in magnetic field - parallel to field
have no force on it
moving charged particle in magnetic field - 90 to field
deflected off course
motor effect
- a current makes a magnetic field
- if this is in another magnetic field the two INTERACT
- this produces a FORCE
flemmings left hand rule
thuMb = Movement
First finger = Field N>S
seCond finger = Current +>-
(MFC)
motor
contains a coil of wire inside a magnetic field
- when a current passes into the coil it produces its own magnetic field
- this INTERACTS causing a FORCE on the wire
- since the current on each side of the wire is in OPPOSITE directions this force is too - causes it to ROTATE
split ring commutator
switches the direction of the current every half turn to keep it spinning
metal/ graphite brushes
feed current into the coil
how to make force on wire stronger
- increase current
- stronger magnet
- more wire in-between magnets
- more turns
how to increase speed of motor
- more coils
- larger current
- stronger magnets
loud speaker
- coild of wire is wrapped around a paper tube attached to the cone
- when there is ac in the coil the cone moves
How loudspeaker produces a sound wave
- direction of magnetic field is changing (AC)
- field of coil INTERACTS with magnet field
- produces FORCE on coil
- direction of force changes
- so cone VIBRATES
- air particles are made to VIBRATE
electromagnetic induction
how electricity is generated
- if magnetic field lines are CUT by a wire
- it INDUCES a voltage + current
how to increase size of current + voltage induced
- faster cutting
- stronger magnetic field
- more turns of coil
generator - how ac current is induced
- spin the coil inside the magnetic field
- direction of cutting changes
- so direction of induced current changes - ac
generator
identical to a motor
