A Faraday cage, also known as a Faraday shield, is an enclosure made of conductive material that blocks electromagnetic fields. It works on the principle that when an electromagnetic field hits something that can conduct electricity, the charges remain on the exterior of the conductor rather than traveling inside. This phenomenon is used to protect sensitive electronic equipment, such as RF receivers, from external radio frequency interference (RFI) during testing or alignment of the device. Faraday cages can be formed by a continuous covering of conductive material or by a mesh of such materials.
Examples of Faraday cages include:
- Small, physical Faraday cages used by electronics engineers during equipment testing to simulate an environment that blocks electromagnetic fields.
- Dual paired seam Faraday bags used in digital forensics to prevent remote wiping and alteration of criminal digital evidence.
- Automobile and airplane passenger compartments, which are essentially Faraday cages that protect passengers from electric charges, such as lightning.
- Microwave ovens, which are a form of Faraday cage that keeps microwaves trapped inside the machine so that they heat food and do not escape out.
- Magnetic Resonance Imaging (MRI) scanners in medical settings, which use Faraday cages to prevent radio signals from entering the room and interfering with the equipment.
Faraday cages work through electrostatic induction, where an external electric field acts upon the electric charges within the cages conductive material, causing them to be distributed in a way that cancels out the external fields effect on the interior of the cage.
