P7 Flashcards
where are the magnetic forces strongest?
at the poles of a magnet
when do magnets exert a force on each other?
when they are close
what do permanent magnets produce?
their own magnetic fields
what is an induced magnet?
an object that becomes a magnet when it is placed in a magnetic field
what does induced magnetism always cause?
a force of attraction
what happens to the induced magnet when a permanent magnet is taken away?
loses some or all of its magnetism quickly
what are the 4 types of magnetic material?
iron
steel
cobalt
nickel
- can all be made into a permanent or induced magnet
what is steel?
an alloy of iron
what is a magnetic field?
a region around a magnet where a force acts on another magnet or on a magnetic material
what does the strength of the magnetic field depend on?
the distance from the magnet
how can the direction of a magnetic field be found?
using a compass
what is the earth’s magnetic field due to?
due to the earth’s core
what happens when a current flows through a conducting wire?
a magnetic field is produced around the wire
what does the strength of the magnetic field depend on? (2)
- the size of the current,
larger current = stronger magnetic field
- distance ,
closer = stronger
what happens when you change the direction of the current?
you also change the direction of the magnetic field
how can you prove a magnetic field around the wire using a compass?
when the current is turned off –> compass needle lines up with earth’s magnetic field
when current is turned on —> compass needle deflects
what rule is used to work out the direction of the magnetic field produced by a wire?
Right hand grip rule
what does the right hand grip rule show?
the direction of the magnetic field produced by a wire
how do you increase the strength of the magnetic field (in an electromagnet)
coil the wire
3 ways to increase the strength of the magnetic field produced by a solenoid
- increase the size of the current
- increase the number of turns of the coil
- place piece of iron inside solenoid –> iron core
what are electromagnets?
solenoid containing iron core
what is the motor effect?
when a conductor e.g a wire is carrying a current, it experiences a force in a magnetic field
when is a magnetic field produced
when a current moves through a wire
what is magnetic flux density a measure of?
the strength of the magnetic field
what is the equation for force?
force = magnetic flux density x current x length
what are 3 factors affecting the size of the force?
- magnetic flux density
- current
- length of conductor
what information can scientist find out about a galaxy when they measure the size of the red- shift the galaxy produces?
its distance from the earth
what does the observation of red shift suggest is happening to the universe?
the universe is expanding
what is the interface?
the boundary between one medium and another
when are waves NOT refracted?
if they are travelling along the normal
