Question

Which of the following must be there in materials that make good electrical insulators?

• A. very few, if any, free electrons
• B. high conductivity
• C. low conductivity
• D. more than 10 electrons
• E. energetic electrons

Answer 1

Answer: (A)

very few, if any, free electrons

Free electrons in a material increases the mobility of flowing electrons into the material. It increases the number of electrons that flow when same potential difference is applied, hence higher current and lower resistance.
Thus the conductivity of material decreases if it lacks free electrons and makes it an electrical insulator.