magnetism (combined science) Flashcards
- what are the two types of magnetic poles
there are two types of magnetic pole: a north pole and south pole
- what are the poles
the poles of a magnet are the places where the magnetic forces are strongest
- what poles attract
poles attract the opposite. for example the north pole of a magnet will attract the south pole of another magnets south pole
- what is the magnetic field
the region around a magnet, where a force acts on another magnet or magnetic material is called the magnetic field
- what does the strength of the field depend on
the strength of the field depends on the distance from the magnet- it is strangest at the poles
- what do permanent magnets do
permanent magnets produce their own magnetic field
- what are induced magnets
induced magnets become a magnet when placed in a magnetic field. when removed from a magnetic field they lose their magnetism quickly
- what is the force between magnets
the force between a permeant magnet and a magnetic material or an induced magnet is always one of attraction
- what do the arrows on field lines do
the arrows on feild lines always run from north to south and show the direction of the force that would act on a north pole placed at that point
- what is the density of field lines called and what odes it indicate
the density of field lines is called the flux density and indicates the strength of the field at that point - the closer together the lines, the higher the flux density
- what happens when the flux density is higher
when the flux density is higher the field is stronger which means the greater the force that would be felt by another magnet
- describe a magnetic compass
a magnetic compass contains a small bar magnet the compass needle aligns with the earth magnetic field and always points to the magnetic north
- what does a magnetic compass do
it provides evidence that the earth’s core must be magnetic
how do we plot feilds
place a bar magnet on a piece of paper
place a compass at one end of the magnet
on the paper, mark where the point of the needle is
move the compass so the tail of the needle is at the point that has just been marked
on the paper, mark a new point where the needle is
repeat and connect the marks until the full field is plotted
how is a magnetic field produced around a wore
whenever a current flows in a conducting wire a magnetic field is produced around the wire
what does the direction of field lines in an electromagnet depend on
the direction of the field lines depends on the direction of the current and can be found with the right hand grip method
describe the right hand grip method
grip the wire in your right hand, with the thumb pointing in the direction of the current
the fingers curled around the wire will point in the direction that the field lines should be drawn
what does the strength of an electromagnetic field depend on
the strength of the field depends on the size of the current and the distance from the wire
how can we see the effect of distance and current
this effect can be seen by placing a magnetic compass at different points along the wire and turning the power supply on and off
when is a solenoid formed
a solenoid is formed when a wire is looped into a cylindrical coil
how do we increase the strength of a magnetic field
shaping the wire into a solenoid increases the strength of the magnetic field, creating a strong uniform field inside the solenoid
to increase the field strength further, an iron core can be added this creates an electromagnet
the solenoid increases the magnetic field because…
it concentrates a longer piece of wire into a smaller area
the looped shape means that the magnetic field lines around the wire are all in the same direction
what is the magnetic field like around a solenoid
the magnetic field around a solenoid has a similar shape to that around a bar magnet
describe how we find the north pole of a solenoid
the north pole of a solenoid can be found with the right-hand grip method
hold the solenoid in your right hand with your fingers following the direction the current flows
your thumb will point to the north pole of the solenoid
how does an electric bell work
when the switch is pushed, the electromagnet is magnetized
the electromagnet attracts the armature
the hammer strikes the gong and breaks the circuit
the armature springs back, completing a circuit again and remagnetizing the electromagnet
the cycle repeats for as long as the button remains pushed
