Electromagnetic shielding is designed to limit the influence of electromagnetic fields and radiation on a device or object. The process uses a barrier made from conductive material containing electric charges of either positive or negative properties at the subatomic particle level. Usually, this material is used to separate the electrical components on the inside of the device from the outside world. Cables also utilize the concept to separate wires from outside environments. When used to block radio frequencies, it is known as RF shielding.
The exact purpose of this shielding is to protect devices from the coupling effect, the transfer of one form of energy to a device that uses a different form. This is commonly caused by radio waves, electrostatic fields, and the full spectrum of electromagnetic radiation. The full level of protection is based on the amount of reduction to the electric and magnetic fields. This depends on the size, shape and orientation of the shielding. No matter the standards in place, however, shielding cannot protect against low-frequency magnetic fields.
A variety of materials can be used as electromagnetic shielding to protect an electrical device. Examples include ionized gas in the form of plasma, metal foam with gas-filled pores, or simply sheet metal. In order for holes within the shielding to be present, they must be considerably smaller than any wavelength from the electromagnetic field. If the shielding contains any openings larger than the wavelength, it cannot effectively prevent the device from becoming compromised.
Household devices often use a different shielding method due to the likelihood of exposure to electromagnetic fields. Plastic enclosures usually use some sort of metallic ink consisting of copper or nickel in a small particular state. This material can be sprayed onto the enclosure, producing a conductive layer of metal that acts as protection. The main reason this layer works is due to its close proximity to the grounding of the device.
Many common day-to-day items contain electromagnetic shielding. One of the most common examples of this is the microwave oven found within most kitchens in the United States. With the metal housing working in unison with the screen on the window, a Faraday cage is created. While some visible light is able to pass through the window screen, waves of other frequencies cannot.