Dielectrics: Feynman's Physics Explained

Feynman Vol II9-10

Put an insulating material — a dielectric — into an electric field and the field inside it weakens. This is because the field polarizes the atoms, stretching them into tiny dipoles whose own field opposes the original. How much the field is reduced is a property called the dielectric constant. This is exactly why a capacitor can store more charge when filled with a dielectric material.

The big idea

Insulators weaken a field by polarizing into tiny opposing dipoles.

Think about it

Why would slipping a sheet of plastic between two charged plates let them hold more charge?

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