Can EMF Travel Through Drywall or Sheetrock?

Current

• An electromotive force is the voltage created by a generator or a battery. It's not really a force in the conventional sense of the word, but you can think about it as a force in the sense that it creates and sustains a current. Drywall and sheetrock are very poor conductors of electricity, so you cannot induce a substantial electromotive force in drywall or sheetrock with a battery or generator -- the material has a high resistance to the flow of current.

Fields

• An electromagnetic field is the combination of an electric field and a magnetic field produced by moving electric charges -- for example, by the electrons traveling through a current-carrying wire. Electromagnetic fields propagate at the speed of light and can penetrate solid objects. Some materials, however, can become polarized by an electric field and thereby create an internal field, which reduces the strength of the external field inside the material. These materials are called dielectrics, and the dielectric constant is a measure of their polarizability.

Behavior

• Like most materials employed in construction, drywall has a relatively low dielectric constants, although their behavior is complex. Nonetheless, electromagnetic fields can indeed travel through drywall and sheetrock -- and indeed, you've probably made use of electromagnetic fields in drywall if you've ever worked with an electronic stud finder, which detects the change in an electromagnetic field that takes place when it passes over a stud. The wooden stud changes the dielectric constant and thus the behavior of the field, causing a light on the stud finder to switch on.

Waves

• Electromagnetic radiation is formed from both electric and magnetic fields, and its ability to travel through drywall depends on the wavelength. Most radiation with wavelengths in the radio region of the spectrum, for example, can travel through drywall, which is why you can listen to the radio inside your house. Radiation with wavelengths in the visible region of the spectrum, however, cannot. Some wavelengths of infrared, by contrast, penetrate drywall better than others.