Magnetism

Force Attractions exist between some metals Force is most concentrated at the ends of the metal object Ends are called Poles (North and South) N pole points north when magnet hangs free Opposite poles attract and similar poles repel

Magnetic Fields Area around magnet that the force acts Can be represented with field lines much like electric field lines Closer lines; stronger field Lines point in direction that a N-pole test would point (toward South)

Earth As A Magnet Earth acts as if it has a large bar magnet imbedded within it magnetic pole geographic pole magnetic pole S N

Earth’s Magnet Magnetism of the earth does not line up with the axis, so the magnetic pole is not the same as the geographic pole Magnetic declination – amount that the compass is off from truly pointing North

Magnetic Materials Ferromagnetic – any material attracted to a magnet or that can be magnetized Atoms of these materials can be thought of as tiny magnets Groups of atoms in the same area are called domains If all domains line up in the same direction, the material becomes magnetized

Creating or Destroying Dropped or heated, loses magnetism If magnet is broken just becomes smaller magnets Created by induction (rub with magnet) Induced from earth (point in same direction as earths magnet and hit it)

Electromagnetism Similarities between magnetism and electricity: –Two types –Likes repel, opp attract –Fields –Can be created by rubbing –Inverse square law

Oersted’s Discovery Whenever electrons move through a conductor, a magnetic field is created in the region around it Field lines are in circles around the conductor As distance from conductor increases, field gets weaker (lines farther apart)

Right Hand Rule Conductor held in right hand with thumb pointing in the direction of the current, the fingers point in the direction of the magnetic field

Coils Magnetic fields around a conductor can be intensified by bending a wire into a loop More loops, greater the intensity Solenoind – large # of loops in a coil Field within the coil is straight and points in one direction

Right Hand Rule Coil grasped with right hand and fingers curled in the direction of the current, the thumb points in the direction of the magnetic field Ends of coils like the poles Direction of current reversed, poles reversed

NS