magnetism

• like poles repel and unlike poles attract
• what is the difference between a contact and a non-contact force?

  contact forces need to touch to act, non- contact forces do not
• is magnetism a contact or non-contact force?

  non-contact
• what is a permanent magnet?

  a permanent magnet produces its own magnetic field
• what is an induced magnet?

  A material that becomes magnetized when placed in a magnetic field.
• what are the 4 magnetic metals?

  Iron, nickel, cobalt, and steel
• where is the field of a bar magnet strongest?

  at the poles
• what happens to the strength of a magnetic field the further away you go from a magnet?

  gets weaker
• what is a magnetic compass made of and the direction it points?

  made of small bar magnet points geographical north but magnetic south
• how can we use a compass to plot the pattern of the magnetic field lines around a magnet?

  place plotting compass near magnet on a piece of paper. mark the direction the needle points. move the plotting compass to many different positions in the magnetic field, marking the needle direction each time. join the points to show the field lines.
• what direction do magnetic field lines go in?

  north to south
• what causes a wire to produce a magnetic field?

  a current flowing through it
• what is the scientific name for a long coil of wire?

  solenoid
• magnetic field inside a solenoid

  strong and uniform
• what kind of magnet has the same magnetic field as the long coil of wire?

  bar magnet
• what is the main advantage of using an electromagnet?

  can be turned off by a switch
• 3 ways to make an electromagnet stronger

  increase current, increase number of turns on the coil, add a iron core
• what rule can we use to draw the magnetic of magnetic field pattern on a straight wire?

  right hand rule
• what do the fingers stand for in flemings left hand rule?

  thumb (motion/force), first finger(field), second finger(current)
• what is the equation for a force on current carrying wire?

  F = B X I X I
• How does an electric motor work?

  a coil of wire carrying current in a magnetic field experiences a force that makes it rotate, a split ring commutator changes the current direction every half turn