INSULATORS

If the people refuse to pass balls along the line in the previous example, the line repre- sents an electrical insulator. Such substances prevent electrical currents from flowing, except possibly in very small amounts. Most gases are good electrical insulators. Glass, dry wood, paper, and plastics are other examples. Pure water is a good electrical insulator, although it conducts some current with even the slightest impurity. Metal oxides can be good insulators, even though the metal in pure form is a good conductor.