The electric field ( ) shown surrounding the wire is produced by the charge distribution on the wire. Both the and the charge distribution vary as the current changes. The changing field propagates outward at the speed of light. There is an associated magnetic field ( ) which propagates outward as well (see Figure 24.6). The electric and magnetic fields are closely related and propagate as an electromagnetic wave. This is what happens in broadcast antennae such as those in radio and TV stations. Closer