No Image Available
Visual representation of Faraday cage
Electromagnetic Shielding Device
Updated September 9, 2025
Faraday cage
A Faraday cage is a metal enclosure that blocks external electric fields. It shields anything inside from electromagnetic radiation.
Category
Electromagnetic Shielding Device
Use Case
Blocking external electromagnetic fields from reaching interior space
Key Features
-
Complete Enclosure Of Conductive Material
-
Blocks External Static Electric Fields
-
Shields Against Electromagnetic Radiation
-
Grounded For Maximum Effectiveness
In Simple Terms
What It Is
A Faraday cage is a special container or enclosure that blocks electric fields and radio waves from getting in or out. Think of it like a shield made from materials that conduct electricity, such as metal mesh or solid metal. When an electric field or a radio wave hits the outside of the cage, the conductive material redirects the energy around the outside of the enclosure, leaving the inside completely protected. It’s named after Michael Faraday, a scientist who first demonstrated this effect in the 1800s.
Why People Use It
People use Faraday cages to protect sensitive electronics from outside electrical interference. For example, they can keep important equipment safe from lightning strikes or powerful radio signals that might cause damage or disrupt function. They’re also used to prevent electronic devices from emitting signals that could be intercepted, which is important for privacy and security. In scientific labs, Faraday cages help researchers conduct experiments without outside electrical noise skewing the results.
Everyday Examples
You might be using a Faraday cage without even realizing it. Microwave ovens have a metal mesh screen on the door that acts like a Faraday cage—it keeps the microwaves inside the oven so they cook your food without leaking out and causing harm. Some people use small Faraday pouches or bags to block signals to their car keys, phones, or credit cards, preventing hackers from remotely scanning them. Even elevators and cars can act as partial Faraday cages, which is why you sometimes lose cell service when you’re inside them—the metal structure blocks the signal.
Technical Details
Definition
A Faraday cage is an enclosure designed to block external static and non-static electric fields by redistributing electromagnetic charges around its exterior. It operates on the principle of electrostatic shielding, effectively creating a barrier that prevents electromagnetic interference (EMI) from penetrating the enclosed space or emanating from within.
How It Works
The functionality of a Faraday cage relies on the behavior of electrical conductors when exposed to an external electric field. When an external field is applied, the free electrons within the conductive material of the cage move and redistribute themselves. This movement creates an opposing electric field that precisely cancels the external field within the enclosed volume. For dynamic or changing fields, such as those from radio waves, the cage must be constructed of a continuous conductor or a fine mesh, where the openings are significantly smaller than the wavelength of the radiation intended to be blocked.
Key Components
Conductive Material: The enclosure must be constructed from a highly conductive substance, such as copper, aluminum, or galvanized steel, to facilitate the free movement of electrons.
Continuous Enclosure: The structure must form a continuous, unbroken shell. Any gaps or seams can act as points of entry for electromagnetic fields.
Electrical Grounding: While not always strictly necessary for basic electrostatic shielding, grounding the cage provides a path for excess charge to dissipate, enhancing its effectiveness, particularly for blocking lower-frequency fields.
Common Use Cases
MRI Suites: Hospital rooms containing Magnetic Resonance Imaging scanners are built as Faraday cages to prevent external radio signals from interfering with the sensitive equipment and to contain the machine's own signals.
Electronics Shielding: Sensitive electronic equipment and testing laboratories are often housed within these enclosures to protect them from external EMI, such as radio frequency interference (RFI) from cellular networks or Wi-Fi.
Critical Infrastructure: Buildings that house vital computing or communication systems, like data centers and air traffic control facilities, are frequently constructed as partial Faraday cages to safeguard against electromagnetic pulses (EMPs).
* Personal Devices: Smaller-scale examples include microwave ovens, which use a perforated metal screen in the door to contain radiation, and bags or cases used to block RFID signals from credit cards or passports.
Help us improve
Was this information helpful?
What could we improve?
Your feedback helps us create better content.
Thank you for your feedback!