Question

What happens when a charged insulator is placed near an uncharged metallic object?

• A. They repel each other.
• B. They attract each other.
• C. They may attract or repel each other, depending on whether the charge on the insulator is positive or negative.
• D. They exert no electrostatic force on each other..
• E. The charged insulator always spontaneously discharges.

Answer 1

Answer: (B)

They attract each other.

When a charged insulator is brought near a metallic object, free charges within the metal move around, causing the metallic object to become polarized. Within the metallic object, the center of charge for the type of charge opposite to that on the insulator will be located closer to the charged insulator than will the center of charge for the same type of charge as that on the insulator.
This causes the attractive force between the charged insulator and the opposite type of charge in the metal to exceed the magnitude of the repulsive force between the insulator and the same type of charge in the metal. Thus, the net electric force between the insulator and an the metallic object is one of attraction.