What Is a Faraday Cage?

A Faraday cage is one of the most important discoveries of the 19th century, designed to protect any object or living being from external electrical charges. The cage is made from conductive materials and can be covered with solid metal plates or built in a mesh (wire grid) structure. When an electrically charged material is brought close, the positive and negative charges inside the cage separate and redistribute across the metal surface, forming an internal electric field in the opposite direction of the external field. This creates a shielding effect that neutralizes the electrical field inside the cage, reducing it to near zero. As a result, the cage protects anything inside from external electromagnetic and electrical interference.

Who Invented the Faraday Cage?
British scientist Michael Faraday, while conducting experiments on electricity and magnetism in the 19th century, discovered that an enclosed conductive structure blocks and redirects disruptive electromagnetic waves. This invention was later named the Faraday Cage.

How Is a Faraday Cage Made?
Copper sheets and metallic plates are commonly used due to copper’s excellent electrical conductivity and strong electromagnetic reflection properties. If built for protecting a building, the structure must be wrapped in continuous, unbroken conductive paths from the top to the ground. The tighter and denser the mesh, the higher the electromagnetic shielding performance. For high-frequency electromagnetic protection, more complex cages may be built using special metal alloys or carbon-based conductive materials.

Where Are Faraday Cages Used?
Faraday cages are widely applied across many industries. Common examples include:

Lightning protection systems in buildings, acting like a paratoner by absorbing and redirecting electromagnetic energy.

Data centers, protecting sensitive electronic equipment from electromagnetic waves.

Prisons and security facilities, blocking mobile and radio signals to isolate the area.

Microwave ovens, which use Faraday cage structures to trap electromagnetic energy inside the device.

Cables and signal transmission systems, reducing electromagnetic interference to ensure safe power or data transfer.

MRI rooms, preventing outside electromagnetic signals from disrupting measurements.

Protective uniforms for high-voltage workers, functioning as wearable Faraday shielding systems.

Faraday bags, used in privacy-sensitive fields (e.g., investigation, intelligence, digital forensics).

Faraday Cage Experiment
A basic Faraday cage can be tested using simple materials by forming a cube-shaped mesh and placing an electronic device (e.g., a mobile phone) inside. When tested externally with another signal-emitting device, it can be observed that the cage weakens or blocks the signal. Increasing wire density improves shielding; decreasing it reduces shielding strength.

Faraday cages have become increasingly integrated with modern technology and continue to expand their role in healthcare, aerospace, security, finance, and advanced electronics, providing reliable electromagnetic isolation and electrical protection.