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Electrostatic shielding
Intermediate
A cavity inside a conductor is field free.
A hollow conductor screens its interior from external fields (Faraday cage). Cars and aircraft protect passengers from lightning in this way.
Mobile signal drops inside a lift.
A cavity with a charge inside has induced surface charge.
In more detail
A conducting enclosure blocks external electric fields from its interior, which is called electrostatic shielding. This is the principle behind the Faraday cage.
Real-world uses
- Car bodies protect passengers from lightning strikes.
- Coaxial cables shield signals from electrical noise.
- Electronic equipment is wrapped in metal mesh, called a Faraday cage, to shield it from external electric fields.
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Frequently asked questions
Does a Faraday cage protect from magnetic fields?
Not from static magnetic fields, but it does block electric fields and some radio waves.
Does the cage need to be solid?
A fine mesh works well for most frequencies.
Does a Faraday cage block all fields?
It blocks electrostatic fields and most electromagnetic interference, but very low-frequency magnetic fields can still pass through.
Related topics in Electrostatics
Field of a charged shell · Field of a uniformly charged sphere · Field of a conductor · Electric potential · Potential difference · Equipotential surfaces