Home Robotics C++ Physics II AP Physics B Electronics AP Java Astronomy Independent Study Summer Session Contests  About
                                                       

Magnets and Magnetic Fields

DIrection of the Magnetic Field                                         Right Hand Curl Rule Video: http://www.youtube.com/watch?v=jCcUochTbVo (4 minutes)

 

 

Defined as: Direction the north pole of a compass needle would point if placed at that point.

Note: It is pointing toward the south pole (opposites attract)

 

 

 

 

What causes Earth's Magnetic Field?
ð Spinning on axis
ð Earth's core: solid inner, liquid outer, mantle

Geographic versus Magnetic Poles.
ð Geographic: Axis of rotation
ð Magnetic: Field lines are vertical

Precession of the Earth
ð One revolution every 26,000 years
ð North star changes

Reversal of Poles
ð Swapping of pole locations
ð In the past 3.6 million years we believe there have
     been at least 9 reversals

Declination angles


ð Angle between geographic and magnetic poles
ð Varies from 0 to 20 degrees depending on location.
ð Navigation maps must be adjusted accordingly.

 

 

Magnetic Field Lines and Right Hand Rule

Left Picture

ð Magnetic field lines around electric current in a straight wire.
ð Note that we are using the direction of conventional current.

Right Picture

Right hand rule for determining the direction of the magnetic field.

ð Point thumb in direction of the conventional current.
ð Fingers wrapped around the wire point in direction of the field.

 

A Magnetic Monopole is a Magnet With Only One Pole: One has Never Been Observed

 

Uniform Magnetic Field: Two Flat Parallel Pole Pieces of a Magnet - Compare with the Lab Exercise