Which statement correctly describes insulators?

• A. Conductors allow charges to flow freely.
• B. Insulators allow charges to move easily.
• C. Semiconductors allow charges to move only at high temperatures.
• D. Insulators - charges cannot move freely; examples include glass, rubber, silk, and plastic.

Answer: (D)

Insulators resist electric current because their electrons are tightly bound to atoms, giving them high electrical resistance. When a voltage is applied, they don’t allow charges to flow freely; instead, the material may polarize, but the actual current remains very small. This is why glass, rubber, silk, and plastic are classic insulators—they’re good at preventing charge from moving through them.

Think of what that means in contrast: a conductor is a material where charges can move freely, so it conducts current readily. Saying insulators allow charges to move easily contradicts their defining property. Semiconductors behave differently: their conductivity depends on temperature and impurities, so they don’t fit the simple picture of insulators.