MadSci Network: Physics

Re: How is a magnetic field related to magnetic poles and lines of force?

Date: Tue Jun 20 06:03:28 2000
Posted By: Jocelyn Wishart, Lecturer, Education, Loughborough University
Area of science: Physics
ID: 957281429.Ph

A magnetic field is the area surrounding (in 3 dimensions) any magnet or 
current carrying wire where a magnetic force can be detected. The Earth 
itself acts as if it contained a giant bar magnet and is totally 
surrounded by a magnetic field.  If you suspend a bar magnet anywhere on 
Earth it will line up with the magnetic field - if you were at the 
magnetic north pole the north seeking pole of your magnet would be 
pointing downwards into the Earth. 

The lines of force or field lines are simply a way of describing the 
extent and the direction of a magnetic field. They are defined as the 
lines along which a tiny bar magnet in the magnetic field would lie along. 
The direction of the magnetic field is given by convention, its the 
direction in which the north seeking pole of the tiny magnet is pointing.  
So the lines of force go from the N pole to the S pole outside a magnet 
but from S to N inside a magnet.

When two magnets are brought close together their magnetic fields interact 
making like poles repel one another and opposite poles attract.

Current theories about magnets are listed  at

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