magnetism

• to make a magnet, stroke a needle with a magnet, repeatedly in one direction only
• a compass is used to find the magnetic field lines around magnets
• opposite poles attract
• stroking a needle with a magnet lines up all the domains and they reinforce each other
• hitting with a hammer will demagnetize
• the earth's magnetic field is caused by molten iron in the core
• stroking with a needle line it up with the earths magnetic field
• north and south pole - north-seeking and south-seeking pole
• there is a magnetic south pole at the geographic north pole
• magnetic metals - iron, nickel, cobalt
• current, core material and coil turns make an electromagnet stronger
• magnetic field lines point from north to south
• steel is an alloy of iron and nickel
• the earth's magnetic field is caused by its molten outer core
• all magnets have a magnetic field
• higher current increases the strength of the magnet
• a permanent magnet has a strong magnetic field without needing electricity
• magnetic field lines never cross
• magnetic field

  
• field line - imaginary line that shows direction of force at any point
• strength of magnetic field = number of field lines per unit area