Question T5A08
From subelement T5 - T5A
Which of the following is a good electrical insulator?
Why is this correct?
Glass is correct because insulators resist electrical current flow by having very few free electrons. Copper and aluminum are metals with many free electrons, making them excellent conductors used in wires and circuits. Mercury, though liquid, is also a metal conductor. Glass lacks free electrons, creating high resistance that prevents current flow, making it ideal for electrical insulation.
Memory tip
Remember the electron availability rule: materials with many free electrons conduct, while materials with tightly bound electrons insulate. This pattern helps distinguish conductors (typically metals) from insulators (typically non-metals like ceramics, plastics, and glass) across all electrical questions.
Learn more
In amateur radio construction, glass insulators are commonly seen on antenna systems and high-voltage applications. The atomic structure of glass has electrons tightly bound in a crystalline lattice, unlike metals where electrons move freely between atoms. This property makes glass essential for RF applications where you need to prevent unwanted current paths while maintaining mechanical support for conductors.
Think about it
Why do you think power lines use glass or ceramic insulators on utility poles rather than just air gaps to separate the conductors?