http://www.ck12.org Chapter 15. Magnetism Version 2
15.1 The Big Idea
For static electric charges, the electromagnetic force is manifested by the Coulomb electric force alone. If charges are
moving, an additional force emerges, called magnetism. The 19thcentury realization that electricity and magnetism
are dual aspects of the same force completely changed our understanding of the world we live in. As with electricity,
we use a field formulation to keep track of magnetic forces. Magnetic fields are usually denoted by the letter~Band
are measured in Teslas, in honor of the Serbian physicist Nikola Tesla; like electric fields, they are vector fields that
contain energy, unlike electric fields, they have three dimensional properties and require some special vector rules to
understand.
Insights due to Ampere, Gauss, and Maxwell led to the understanding that moving charges — electric currents —
create magnetic fields. Varying magnetic fields create electric fields. Thus a loop of wire in a changing magnetic
field will have current induced in it. This is calledelectromagnetic induction.