Nonmetallic conductors, such as conductive plastic, are sometimes used. Capacitance occurs between any two conductors separated by an insulator. They are materials that have properties that are intermediate between conductors and insulators. Materials made of metal are common electrical conductors. The nonconductive boards support layers of copper foil conductors. The conductors and leads introduce undesired inductance and resistance. The phosphors are usually poor electrical conductors. Two of the three circuit conductors are operated as a bipole. These generated radio waves by a high voltage spark between two conductors. It applies to both metal conductors and circuit components (resistors) specifically made for this behaviour. An antenna typically consists of an arrangement of metal conductors. Longer wiring runs are more limited by voltage drop in the conductors. She quickly became a favorite of many conductors and composers of major European orchestras. She worked with many composers, producers and conductors. Metals are relatively good conductors of heat.