A Faraday cage is a covering or mesh-like structure made of a conducting material that shields anything placed inside it from the effect of electric fields. They cannot annul static or slowly varying magnetic fields. However, if the conductor is significantly thick, then they can protect their interiors from external electromagnetic radiation to a large extent. In case the cage is a mesh, the diameter of the holes should be much smaller than the wavelength of the radiation to display the said property.
Faraday cage is named after its inventor, the English scientist Michael Faraday. In 1836, he observed that an excess charge on any hollow conductor remained on its surface and did not affect anything placed within it. For the purpose of demonstration of this fact, he built a room covered on the exterior with metal foil and subjected it to the electric field created by high-voltage discharge from an electrostatic generator. With the aid of an electroscope he successfully showed the non-existence of any charge inside the walls of the room.
Although this effect has been attributed to Faraday, its existence was first shown by the American polymath, Benjamin Franklin. He had lowered an uncharged cork ball suspended by a silk thread through an opening on a charged metal can. The ball was not attracted to the walls of the container as expected. This proved the scientific fact that no electric field resides within a charged hollow conductor
How does it Work
When a Faraday cage is placed in an external electric field, then the electrons on the conductor redistribute themselves in such a way that they neutralize the effect of the field in the interiors of the conductor. As a result, any object within the cavity of the conductor remains shielded from electric field effects.
Faraday Cage to Restrict EMP
An EMP or electromagnetic pulse is a short burst of electromagnetic energy. This natural or man-made phenomenon can disrupt or damage various electronic equipment, even aircraft structures and buildings when associated with high levels of energy. A Faraday cage can save your gizmos from its hazardous fluctuating electric fields.
Faraday Cage for Cell Phone
You can keep your cell phone safe from lightning with the help of these specialized cages. Additionally, in case you seek privacy, the radio signals which are essential for communication of the mobile device are also guarded by it. This makes your cell phone, potentially dead, unable to receive or send any signal.
You might argue that why not just switch off your phone to achieve the end? Well, certain technologists say that a turned off phone might get turned on spontaneously on receiving certain data through the Internet on a wired Ethernet network or by pressing certain emergency keys. That is something which the meshed enclosure will not allow. The meshed enclosure comes to the rescue by blocking all radio, GPS, satellite, Bluetooth and Wifi signals.
Faraday Cage Wallet
Faraday cages in the shape of wallets act as good RFID blockers for your ATM cards, driver’s license, credit cards and passports. These articles of our daily use commonly have RFID chips in them which can be maliciously intercepted or scanned to track down your personal particulars.
Faraday Cage Bag
Any ordinary shopping bag, pocketed garment, pouch or backpack with an inner lining of multiple layers of aluminium foil can act as Faraday bags. If electronically tagged items are carried in such bags, they skip detection by security panels at store exits or electronic toll collection devices. This property, unfortunately, can be used unethically by shoplifters and dishonest persons wanting to avoid toll tax.
Microwave Faraday Cage
If you look closely at a microwave door, you will find a metallic mesh on the inside.The remaining three walls are made of solid metal. If the diameter of the holes meet the qualifying criteria, the equipment can function as a Faraday cage. Though most of the commercial Faraday cages are made of copper, the aluminium or steel window screens of microwaves can significantly block bulk electromagnetic radiation.
Faraday Cage House
Proximity to high tension wires, power lines, cell towers and dozens of electronic devices makes your house an abode of electromagnetic radiation, which, according to some technologists could disturb an individual’s sleep pattern. Though its contribution to causing cancer is debatable, still, many people prefer to include a metallic mesh in their building material, to keep their homes safe from any electromagnetic disturbance. EMF bed canopy sheets fulfill the same purpose.
Faraday Cage Car
The metallic body of a car behaves like a portable Faraday cage and can effectively protect you against lightning while driving. However, it should be borne in mind that convertibles lack a metallic roof, compromising on the Faraday cage effect. Same goes for cars made of poor conductors or insulators.
In case a lightning strikes your car, some of the current can also pass through the metal appendages and electrical equipments of the vehicle such as door handles, foot pedals, cell phone chargers, GPS units, etc. Hence, ensure safety under such conditions by folding your hands on your lap to avoid touching anything metallic in the car. No touching the radio or talking on cell phone either. Once the current has passed through the vehicle and entered the ground, you might exit the car, not before that.
Faraday Cage Suit
Linemen wear suits designed as Faraday cages while working with high voltage power lines, to protect themselves from getting electrocuted.
Some people wear hats lined with aluminium foils nurturing the belief that it protects the brain from electromagnetic radiation, brain reading and brain control. This is only limited to followers of some ritualistic practices.
In addition to these, though some companies claim to sell protective clothing with inbuilt Faraday cages, wearing them is not recommended by some experts due to harmful effects of heat buildup in the body and effective inability to protect all parts of the body from electromagnetic radiations. Some paints also come impregnated with aluminium and copper fibres preventing radio wave transmissions.
MRI scans take the help of this structure to get accurate data from the scanned patient. Aircrafts are frequently struck by lightning but are still safe to travel in due to their aluminium hulls which act as the cage. Nested meshes offer an even better safeguard. Tests have shown that even the high levels of electricity produced by Tesla coils can be stopped by this device. Experiments on electrophysiology are conducted in chambers having the said property. Generators are placed within Faraday cage boxes for smooth performance.
Keeping in view the hoard of benefits to mankind, the device can be termed as an important invention in the field of Physics with an ever widening effect on our daily lives.
Article was last reviewed on Wednesday, December 6, 2017