Magnetism and the Electromagnetism Flashcards
what is a magnetic field
the region around a magnet where other magnets experience a non-contact force acting on them
what do permanent magnets do
produce their own magnetic field all the time
what do induced magnets do
they create a magnetic field when they’re in another external magnetic field
what happens when an external field is removed
magnetism is mostly lost
what are magnets made of
magnetic materials such as iron, nickel and cobalt
what determines how quickly magnetism is lost
the ‘softness’ of the material
why are permanent magnets made out of steel
they are magnetically ‘hard’ as they take long time to lose magnetism
what is the needle in a compass
a small bar magnet which always points in the direction of the magnetic field it is in
how do you find the shape of a magnetic field
- Put the magnet on paper and draw around it
- Put the compass near the magnet on paper and mark the direction of the compass with one dot at each end of the needle
- Move the compass so the needle south is at north dot and then repeat step 2
- Repeat step 3 all around the magnet and join the points
what direction does a compass, when it is not near a magnet, point
North
why does a compass, when it is not near a magnet, point North
because it is attracted to the magnetic field of the Earth
what happens when a current flows through a conductor
a magnetic field is created around it in concentric circles perpendicular to the conductor
what is the right hand thumb rule
point your right hands’ thumb in the direction of the current and curl your fingers. The direction of your fingers is the direction of the field
what happens to the strength of the magnetic field when there is a larger current or its closer to the wire
stronger magnetic field
what is a solenoid
a coil of wire used in the construction of electromagnets
what happens to the field lines in solenoids
field lines around each loop of wire line up with each other
what happens in solenoids when the wire’s wrapped into multiple loops
the field lines overlap and interact
what happens inside solenoids
field lines point in the same direction and magnetic field lines are strong, almost uniform
what happens outside solenoid
overlapping field lines cancel out, point in different directions so break apart from the ends of solenoid
how do you increase the strength
more turns
add an iron core
increase the current
what are magnets used for
the force of attraction between two magnets used to keep fridge doors closed
magnets are are used to make magnetic separators, used in recycling plants to sort metal items
what is the motor effect
when interacting magnetic fields around two separate objects results in the movement of one of the objects
how do you increase the force
increase the strength of magnetic field or use higher current
force =
magnetic flux density x length of wire x current
what is flemings left hand rule
current must be flowing perpendicular to magnetic field
thumb = direction of force
index finger = magnetic field direction
second finger = direction of current
