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Polarisation
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Alignment of dipoles inside a dielectric.
In an electric field the charges in a dielectric shift slightly or its molecular dipoles align, producing an internal field opposing the applied one. The net field is reduced to E₀/κ.
Polar molecules rotate; non-polar ones are stretched.
Polarisation is proportional to the field for linear materials.
In more detail
Polarisation occurs when an electric field shifts charges or aligns molecular dipoles in a material. The induced dipoles produce a field that partly opposes the applied field.
Real-world uses
- Polarisation explains why charged objects attract neutral ones.
- Polymer materials are chosen for their polarisation properties in capacitors.
- Electrical insulators in cables become polarised when placed in an electric field, which reduces the field inside them.
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Frequently asked questions
Why are neutral objects attracted to charge?
The external charge polarises them, creating induced charges that attract the object.
Does polarisation need a permanent dipole?
No, induced polarisation occurs in all materials, though permanent dipoles add to it.
What is polarisation?
The shift or alignment of charges or dipoles in a material in response to an applied field.
Related topics in Electrostatics
Energy in a capacitor · Energy density of field · Dielectrics · Dielectric breakdown · Spherical capacitor · Cylindrical capacitor