Physics Notes - Herong's Tutorial Notes - v4.01, by Herong Yang
What Is Magnetic Field
This section provides a quick introduction of magnetic fields.
What Is Magnetic Field? A Magnetic Field is the distribution of magnetic influence in space. Magnetic fields can be created by magnets. This magnetic influence shows up as force in 3 ways:
- Attract or repel magnets and magnetic material.
- Apply torques on magnets to twist them.
- Deflect moving electric charges.
What Are Magnetic Lines? Magnetic Lines are continuous directional lines plotted in the space to represent a magnetic field. At each point of a magnetic line, the direction of the line represents the direction of the magnetic influence. The density of lines in an area represents the strength of the magnetic influence.
Magnetic lines are always form closed loops. Some portions may go through inside the magnetic object or device that creates the magnetic field.
The diagram from hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemag.html shows two examples of magnetic fields represented by magnetic lines. The one on the left is created by electric current in a solenoid coil. The one on the right is created by a magnet bar. Their magnetic lines have almost identical patterns.
Here is another magnetic field example from faithfulscience.com/classical-physics/electric-and-magnetic-fields.html. It is created by electric current running a straight wire.
Table of Contents
Introduction of Frame of Reference
Magnetic Force on Moving Charges
Moving Charge Creating Magnetic Field
Biot-Savart Law for Magnetic Fields
Magnetic Fields of Current Carrying Loops
What Is Magnetic Dipole and Moment
Introduction of Special Relativity
Time Dilation in Special Relativity
Length Contraction in Special Relativity
The Relativity of Simultaneity
Minkowski Spacetime and Diagrams
Introduction of Generalized Coordinates