Faraday Cage demystified.

Hi folks.

Electricity is the lifeblood of many aspects of our world. Without volts and amps, many of our technological innovations would fail to exist. Even our bodies wouldn't function without an electrical charge zipping through our cells and neurons. But what electricity gives, electricity can take away. Although this form of energy is vital to so much of our lives, it's one of those things that are only good in the right amounts. Too much electricity can electrocute people. Likewise, it can kill our modern electronics and machines.

So what saves linemen working on 765 KV line? What saves us from the high energy radiations inside the microwave oven?

Thanks to Michael Faraday, the brilliant 19th-century scientist, and one of his namesake inventions, the Faraday cage, we humans have developed plenty of ways to control electricity and make it safer for our computers, cars and other inventions and for us, too. Faraday cages shield their contents from static electric fields. An electric field is a force field surrounding a charged particle, such as an electron or proton.

Electromagnetic radiation is all around us. It's in visible and ultraviolet light, in the microwaves that cook our food and even in the FM and AM radio waves that pump music through our radios. But sometimes, this radiation is undesirable and downright disruptive. That's where Faraday cages come in.

It is nothing but a net woven from metal wires and object kept inside is protected from the field present outside or vice versa (microwave ovens case). The gap between the wires should be less than the wavelength of the radiation to be blocked. As a Faraday cage distributes that charge or radiation around the cage's exterior, it cancels out electric charges or radiation within the cage's interior. In short, a Faraday cage is a hollow conductor, in which the charge remains on the external surface of the cage. It works best when grounded as it can direct all induced currents to ground.

A lot of buildings act as Faraday cages too, if only by accident. With their plaster or concrete walls strewn with metal rebar or wire mesh, they often cut down wireless Internet networks and cell phone signals (radio waves have wavelengths in few meters that is more than the distance between the iron strands).But the shielding effect most often benefits humankind. Microwave ovens reverse the effect, trapping waves within a cage and quickly cooking your food. Screened (faraday cage used as coating) TV cables help to maintain a crisp, clear image by reducing interference. (See for yourself in case you find a waste piece of one!)

Power utility linemen often wear specially made suits that exploit the Faraday cage concept. Within these suits, the linemen can work on high-voltage power lines with a much-reduced risk of electrocution.

Governments can protect vital telecommunications equipment from lightning strikes and other electromagnetic interference by building Faraday cages around them.  Also you'll find Faraday cages in the form of MRI (magnetic resonance scanning) rooms. MRI scans rely on powerful magnetic fields to create medically useful scans of the human body. MRI rooms must be shielded to prevent stray electromagnetic fields from affecting a patient's diagnostic images.

All modern armed forces depend on electronics for communications and weapons systems, but there's a catch --these systems are vulnerable to high EMPs (electromagnetic pulses). Electromagnetic bomb (E-bomb) is used to create these pulses and destroy the communication networks of the enemy. To safeguard critical systems, militaries sometimes use faraday cage shielded bunkers and vehicles.

We will talk more about making your own faraday cage and electromagnetic bomb in coming articles. Thank you for your time and please feel free to post about your areas of interest.