CoachAn insulator is a material that blocks electricity. Bridging the gap with an insulator leaves the loop as open as before: the bulb stays dark.
Examples
Example 22.4 (A morning of tests)
Results from a classroom tester: a steel paperclip — light. A coin — light. Aluminium kitchen foil — light. A key — light. A plastic ruler — dark. A wooden pencil — dark. A glass marble — dark. A rubber eraser — dark. A strip of paper — dark. The pattern jumps out: the objects that light the bulb are all made of metal.
Example 22.7 (Anatomy of a wire)
Look at the end of a lamp’s cable where it enters the plug: inside runs shiny copper — a conductor, the current’s road; around it wraps colored plastic — an insulator, the road’s fence. The copper does the work; the plastic keeps the current in and your fingers out. Every cable in your house pairs the two: a conductor inside an insulator.