A compass is a navigational tool for identifying directions on Earth's surface.  A compass consists of a tiny magnetized "needle" which is free to rotate around a fixed point in the centre.  Being free to move, the needle will align itself with Earth's magnetic field.  This fact makes a compass a useful tool for understanding position and direction of motion relative to a common, fixed point, such as the geographic North Pole of Earth.

 

Another less known fact is what happens to a compass needle if you place it near a current-carrying wire.  The needle will quickly swing around to a point perpendicular to the conductor. If the needle's movement is a reaction to a current-carrying conductor, does that mean Earth is a giant conductor?  How can Earth and a current-carrying conductor both have magnetic fields?  What are magnetic fields and how are they produced?

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In previous lessons you learned about gravitational fields and electric fields.  In this lesson you will explore the magnetic field.

 

In this lesson you will answer the following essential questions:

  • What is a magnetic field?

  • How is Earth's magnetic field produced?

  • What is the significance of a current-carrying conductor inducing a magnetic field?