magnetism Flashcards
what is a magnet?
any material or object that produces a magnetic field
if the field lines are more dense what does this mean?
the magnetic field is stronger in that area
like poles will….
repel
opposite poles will…
attract
how do you find the poles of a magnet using a compass?
the needle of the compass is a tiny bar magnet and so you line up the compass with the field lines of whichever magnetic field its in,and the compass will always point towards the south pole.
what is a magnetic material?
any object that can be influenced by magnetic fields and has the potential to become a magnet
name 4 magnetic materials?
-cobalt
-nickel
-iron
-steel
what is a permanent magnet?
a magnet that produces their own magnetic field all of the time and it cannot be turned on and off
what is an induced magnet?
an induced magnet is made when a piece of magnetic material is put into the field of a permanent magnet,and only has a magnetic field temporarliy.
what will the force between a permanent and induced magnet always be?
attractive-they will not repel from each other.
what does magnetically soft mean?
when induced materials lose their magnetism really quickly
name two magnetically soft material
-nickel
-iron
name a magnetically hard material
-steel
what is electromagnetism?
where electric currents produce their own magnetic field
what rule do you use to find the direction of the magnetic field in a wire?
right hand rule
give two properties of a solenoid
the magnetic field within a solenoid is strong and uniform
how can you reverse the direction of the magnetic field in a solenoid?
reverse the direction of the current flowing
how can you increase an electromagnets strength? (4)
-increase the current
-increase the number of coils(solenoid)
-decrease the length of the coil(solenoid)
-add an iron core
give the iron filings method to find the shape of a magnetic field around a bar magnet
-place the magnet under a piece of paper
-sprinkle iron filings on the paper
-tap the paper to evenly distribute the iron filings and align them with the magnetic field
give the plotting compass method to find the shape of a magnetic field around a bar magnet
-place the magnet on a piece of paper and draw around it
-place the plotting compass close to the magnet and mark where the needle points
-move the plotting compasses around the magnet and repeat many times to build up a magnetic field pattern
what is the role of the split ring commutator in a dc motor?
the split ring commutator swaps the positive and negative connections every half turn
how does the split ring commutator prevent the coil never turning 360 degrees?
the split ring commutator swaps the positive and negative connections every half turn so that the direction of the current also swaps every half turn,this ensures the force acting on the coil will always be acting in the same direction allowing the coil to rotate in the same direction.
how can you increase the speed of rotation in a dc motor?(3)
-increase the current
-add more turns to the coil(while keeping the length of coil the same)
-increase the magnetic flux density(use a stronger magnet)
what is the motor effect?
the idea that a current carrying wire in the presence of a magnetic field will experience a force
