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Electromagnetic Fields (EMFs) Explained – Easy To Understand Definitions

Posted by Lloyd Burrell on May 17, 2013 under EMF facts | 29 Comments to Read

I know reading about EMFs can be heavy going.

Even confusing.

It took me a long long time scouring articles, books and websites to get clear on a lot of this.

To demystify things I’ve drawn up a list of definitions.

SIMPLE ones.

These aren’t textbook definitions.

The idea is to explain using terms you can easily understand.

Because the more you understand the more effectively you can deal with EMFs.

If there any definitions missing from this list let me know in the comment box at the bottom of the page and I’ll add them in!

Alternating current

An electrical current that changes strength and direction of flow with a certain regular cycle. For example, 60 Hertz AC is an electrical current that changes its polarity (from positive to negative and back to positive; a complete cycle) sixty times per second.



A unit of measure for electric current. Amperes or amps are quantity. Thought of in terms of water, amps are like gallons or buckets (volts are the pressure – see below).



Amplitude is the measurement of the maximum of peak displacement compared to the zero rest level, that’s to say its the height of the wave. The unit of amplitude varies with the kind of waves we are talking about. E.g. The amplitude of an electric field is measured in V/m.



An antenna is a conductor that can send and receive EMFs such as microwave, radio or satellite signals. A high-gain antenna increases signal strength, a low-gain antenna receives or transmits over a wide angle.  Also called an aerial.



Attenuation is the opposite of amplification. It means reduction in signal strength. For RF shielding products the attenuation is commonly expressed in decibels (dB) at a certain frequency because the attenuation changes according to the frequency.


Attenuation Specification

The attenuation specification for a shielding material indicates how much radiation penetrates through the shield.


Bus or busbar

A bar with screw connections for either neutral or grounding conductors.



As far as electricity goes in the US this refers to the National Electrical Code (NEC), which is revised every three years.



Any material which passes electrical current. Metal is generally used as a conductor – other substances such as the earth or the human body can be good conductors which partly explains the health issues with EMFs.



Typically metal pipes for carrying electrical wiring though they can be made of PVC or other materials. They can act as grounding conductors for electrical circuits in some circumstances.



An electric current is a flow of electric charge through a power line or an electric wire. Like water flows through a pipe an electric current flows in a wire. Where currents flow magnetic fields are produced.


Direct current (DC)

An electric current that flows in one direction only, as opposed to AC which flows back and forth.


Distribution lines

Lines carrying power to neighborhoods (primary distribution) and to one or several buildings (secondary distribution).


Directional EMF Meter

A directional EMF meter can detect EMFs from a given direction as opposed to an omni-directional (or triaxial) meter which at any time gives the reading of the EMFs coming from all directions in a given position. It may be seen as an advantage for a RF meter to be directional because it allows you to determine the direction of the RF source.



English term for ground.


Electric field

A zone of potential difference between oppositely charged conductors or between conductors and ground. It’s measured in volts per meter or V/m. Electric field is a function of voltage and not of current.


Electromagnetic Fields

An electromagnetic field, also called an EMF, is a region of space where electric and magnetic forces interact. Often used to refer to the general phenomena associated with fields spreading out from conductors or antennas, depending on the frequency.


Electromagnetic spectrum

The electromagnetic spectrum or EMF spectrum is used to show the relationship between different types of EMFs according to their frequency and wavelength.



Extremely low frequencies are in the range 1-300 Hz though sometimes defined as being up to 3kHz. Your homes’ electrical wiring (60Hz in US) is in this ELF range.



EMFs are expressed in terms of their frequency and wavelength. Frequency is how many complete waves go by per second. This rate per second is expressed in Hertz (Hz).



A unit used for measuring magnetic field strength (flux density). Milligauss (mG) is more commonly used for measuring health impacts. One gauss equals 1,000 milligauss. Tesla or microTesla is used more commonly in Europe. 1 µT (microtesla) = 10 mG (milligauss)



A device used to measure magnetic field strength.



Used as a verb or noun. As a verb it means to connect in some way to either earth or to a conductor which serves in place of the earth. Sometimes used when the more accurate term would be “bond.” N.B. it is not the earth connection which protects a circuit from a “ground fault,” but a solid connection back to the transformer neutral.



Harmonics and transients are a form of “noise” or “distortion” which attach to the fundamental wave, thereby producing a distorted waveform. Commonly known as dirt electricity.



Used to measure the rate at which charge changes polarity of an AC electric current. One Hertz is one cycle per second.



As a noun it refers to the ungrounded circuit conductor carrying the voltage.



A material which is a poor conductor of electric current.


Magnetic field

A zone of energy which accompanies every electric current. Can be an AC or DC magnetic field (MF) – measured in milligauss.


In the US the FCC (Federal Communications Commission) defines “microwaves” as a subcategory of RF radiation operating at frequencies ranging from about 1 GHz upward



One-thousandth of a gauss (mG).



Or neutral conductor. The common term for a grounded conductor (GC), white in the US.


Non-ionizing radiation

Ionizing radiation has the ability to break molecular bonds, non-ionizing radiation was once considered safe because it can’t do this.


Usually refers to one of the voltage carrying conductors in a power line or in an entrance cable to a building.



The positioning of each phase of the circuit on a utility line with respect to the other phases so as to minimize EMFs through cancellation.



A term for energy which leaves its source and travels. Power frequencies as found in electrical wiring generate negligible radiation. Radio frequencies and above are true radiating sources.


Radio Frequency Radiation (RF)

These are high frequency EMFs in the range 10 MHz-300 GHz. This category of EMFs is transferred through the air; the term “wireless” is often used. They relate essentially to telecommunication devices like cell phones, WiFi etc.



The property of a material to resist the flow of electrical current.  Current flowing through resistance always results in dissipation of energy usually in the form of heat.


Service Drop

The overhead which brings power to a residence or business from the distribution line. It usually attaches to the eave of the building if overhead.



Methods used for reducing EMF exposures.


Short circuit

An unintentional connection between hot and neutral conductors in a circuit or between two hots.


Switched Mode Power Supply (SMPS)

A device used to convert electrical power and commonly found in many modern electrical devices that work at low voltage including smart meters, DECT phone chargers, computers etc. SMPS converts voltage and current (AC to DC) by constantly switching the source on and off to supply the needed voltage at the output. This switching can create dirty electricity. The alternative, linear mode power supply avoids this problem by offering a constant voltage but is less energy efficient and more expensive.

Stray Voltage

A misnomer, neutral current does not stray, it follows all available paths to complete the circuit back to the transformer or substation.


Tri-axial EMF Meter

A tri-axial EMF meter is a meter which gives a reading based on the 3 axes (X,Y and Z). To obtain the equivalent with a single axis meter, in any given location take measurements on the x, y and z axes, square these numbers then add them together and take the square root.



A large unit of measure for magnetic fields. One tesla (T) equals 10,000 gauss. One microtesla equals 10 milligauss.


Three-Phase Service

A service that brings in all three phases from the power line plus the neutral. Common in commercial buildings.
Two-Phase Service

Service that brings in two of the three phases from the power line plus a neutral.  This type of service always produces significant neutral current since the two phases never balance.


Very Low Frequency (VLF)

EMFs in the frequency range of  3 kHz to 30 kHz.



Used to measure electrical potential. Its the electrical force which propels current in a conductor. The usual comparison is with water. A volt is the pressure, like psi in water, but applied to electrons.


Volts per meter

Electric fields are usually measured in volts per meter (V/M).



The distance between waves. As frequency increases,  wavelength decreases, and vice versa. At 60 Hz the wavelength is approximately 3,100 miles. At radio frequency ranges the wavelength is closer to thirty or forty feet.


If you’re looking for more developed definitions I recommend you read Tracing EMFs in Building Wiring and Grounding by Karl Riley, which served as my reference guide in preparing the above.

  • Lucy said,

    Hi Lloyd,

    First of all, thank you for all the information that you freely supply on this site. There is so much useful information on here and I have recommended it to a number of friends concerned with EMF exposure.

    My question is related to the new iMAC computer. I’m a professional graphic designer which unfortunately means I’m on the computer a lot. I’m about to purchase a new desktop computer (iMAC) but I’m wondering if there are certain brands that have better EMF ratings than others.. Is this something you’re aware of? Also, would you say that the bigger the computer the higher exposure to EMFs?

    Many thanks

  • Lloyd said,

    Hi Lucy
    At the moment suppliers are not required to disclose EMF information on computers so the only way you can obtain this information is to measure with an EMF meter. Distance is important…its an effective way of reducing EMF exposures….so whatever enables you to put more distance between the computer components and where you sit is a good thing….the particularity of the iMac is that all the electronic components of the computer are in the screen housing….which means you have to have it at 3/4 feet maximum to be able to see it….for this reason a computer which enables you to set the CPU further away is safer. Bigger does not necessarily mean more EMFs…there’s no rule of thumb here.

  • Lloyd Burrell said,

    Hi Lucy
    Thanks a lot for your donation! Appreciated. Thanks.

  • Marina said,

    Dear Lloyd,

    Also, thank you so much for this and all the information you give us so willingly.

    I am living in a house with electric heat and a digital meter and I was getting surges up to and over 500 on a Stetzerizr Microsurge Meter. I used absorbers to keep the counts down but I don’t have enough absorbers.

    Right now the outlets that have no absorbers are measuring over 1900. In the past week I have gotten extremely ill, I can hardly see, and my gut and head feels like it will explode and I am extremely hot inside. I tested the outlets and I cringed to see readings over 1900 when it should probably not be over 15 for me with 15 heavy metals in me, including mercury.

    A Power employee came and poo pood my meter and the absorbers and had never heard of Graham Stetzer so he will be back on Monday with his meter which is the only meter he trusts. I told him that surges this high go on for hours but at 5:00 am this morning they were all low.

    I need a safe place to live but I am so sick and my adrenals are so low, I’m having a hard time getting my head to think straight.

    Thank you again. I have to get another meter that does not have to be plugged in and more absorbers.

    Life is just too, too complicated!

    Again, thank you!


  • Lloyd said,

    Hi Marina
    GS filters are only feasible up to a point. Given your readings you might want to consider installing a line conditioner, which is a more heavy duty solution. See Send them an email, see what they suggest.

  • Lloyd said,

    Hi Betsy
    The options are either you move house or you continue trying to clean up your electrical supply. If you take the second option, make sure you have eliminated everything in your own home that could be causing this problem, see….then try installing more filters, the manufacturers recommend up to 20. You should get at least a 20% reduction in GS units with each new filter so this will tell whats achievable with the filters. I know the power company employee was ignorant on the issue but you need to send the head office a registered letter. If the power coming into your home already has these high levels of DE they must deal with this – despite what the power company employee said, they are well aware of the issue and have been using industrial filters for decades.

  • Betsy said,

    I just spoke with the distributor for the sola/hd company that you referenced for the hardwired power line conditioners. They referred me to the manufacturer for information. I spoke with a person at the company that makes these products. Basically, he explained to me that the hardwired power conditioners can not be used for general home use if they are going to be connected to anything that has inductive loads like a refrigerator or where there is an initial larger current draw. He said it would cut off the power. He did suggest using the portable power conditioners for things like electronics in a home office or a home theater/tv. I may have not used the correct terms but I think this is the basic information. Do you have any additional comments on this.
    Started my journey after getting sick from a Chicago water smart meter. Since then the gas company has added another one, and now ComEd is on the move to install the electric meters in Chicago. Never in my life did I think something like this would be happening to the worlds population!

  • Linda said,

    Hi Lloyd,
    we just purchased a Trifield 100XE meter. Wow! the scariest was the electrical. We have ceiling cable heat. What are the dangers of this type? The heat is not even on and it went off the meter for electrical,but no magnetic. Short of selling our paid for home (we are 65 and 70)is there a solution? My husband laughed and said maybe we should be wearing tinfoil hats!

  • Lloyd said,

    Hi Linda
    Electric fields are present in a cable when a device is plugged in, even if the device is not switched on and in use – this is why you are getting high readings from your ceiling cable – these EMFs are dangerous. There are 2 solutions 1. shield, most materials shield electric fields or 2. switch off the circuit breaker, so go to your electrical box and cut the power to ceiling cable. If you do decide to shield you need an EMF meter to test before and after shielding.

  • Bill said,

    Is it dangerous to have an antenna for digital TV on the roof of my home. I wondered if it is just another way to pick up harmful EMF radiation. Thanks Bill

  • Lloyd Burrell said,

    Normally a digital TV antenna only receives a signal……it does not transmit….so there danger/exposure is very limited.

  • Susan Burke said,

    Thank you. RF meters emit a frequency that is too high for our bodies. Some meters are referred to as ERT or RF meters. They are still “smart meters”, don’t let the utility company fool you are talk you into believing they are harmless. All of these wireless meters have radio transmission frequency and antennas and according to the FCC part 15, subpart C, they are not supposed to be placed in our homes without proper oversight, regulations, permission and permits. I am initiating a class action lawsuit on long Island against the SCWA for the lack of disclosure and transparency, as they installed on of these meters in our basement without our knowing it and it made me sick for two years. We found it Nov. 3, covered it with aluminum, but then went a step further and disarmed it altogether. It is amazing, my symptoms are all but gone. Just need to keep the use of this computer to a minimum, hardwired the mouse and keyboard, need to hardwire the monitor. Stop the installation of smart meters, learn how to block them or have them removed. Call and fight for this right to be free from smart meters on your homes. Please!

  • Lloyd Burrell said,

    Thanks for sharing Susan. One distinction I’d like to make to avoid confusion:
    RF meter = an EMF meter you use to take readings of radio frequency radiation
    smart meter = wireless utility meter being forcibly installed in peoples homes

  • Christel said,

    I measured a digital TV that was seemingly run from a wifi router/computer and unless there was another source of microwave radiation in that area of the room, the TV seemed to be emitting microwaves. Digital TVs may not emit microwave radiation, but they do cause dirty electricity which causes health problems all by itself. For that you need a Stetzer meter.

  • Lloyd Burrell said,

    Quite right Christel. In my comment to Bill I should have said “the danger/exposure from RF radiation is very limited but the risk of exposure from dirty electricity is a possibility”.

  • George Ainsworth said,


    “In the struggle against lies, art has always won
    and always will …. Lies can stand up against much in the world,
    but not against art.”

    Alexander Solzhenitsyn,
    Noble Prize Acceptance Speech, 1970

    Check out this video on Vimeo,
    The Apologia of Thomas Alva Edison.
    We are about to complete the second part
    of War of the Current, Tesla’s Engine.
    Would love to talk about linking to your
    site from ours when we stream this movie.

    See Tesla’s Engine Facebook page for more info.

    Thank you for what you do.

    George Ainsworth
    Mt. Shasta Film Works

  • Lloyd Burrell said,

    Hi George
    Yours looks to be an interesting and valuable contribution.

  • Gustavo said,

    Hello Lloyd!

    On this article you mention about conduits. I wonder what kind of conduit would be better for blocking EMF from the wires inside them: PVC, iron, copper, aluminum or other material?

    Also, what is a good way to shield a fuse box? My fuse box is in the room where I work and unfortunately I can’t move my office or the fuse box.

    Thanks so much!

  • Mitchell said,

    Thanks for the definitions, very helpful.

    I have a Trifield 100xe meter. Can I measure dirty electricity when this meter is placed in front of a plug?

    If so, would I take the reading from the top scale, then multiply by 10 to get a number that can be compared to what comes out of a Stetzerizer meter?

  • Harsha Vardhana R said,

    Hi Lloyd!

    Thanks for the basics which makes us easier to read any other info on EMF.

    I have heard that Microwave cooking is harmful for health and one needs to stay away. My electrician replied that Induction Cooking is equivalent to MW Cooking and that was a shocker for me.

    Can you please clarify.


  • Lloyd Burrell said,

    There are lots of good reasons not to use a microwave oven…..RF radiation and magnetic fields for starters, I wrote about this in detail see
    Induction hobs are a different animal….. they generate EMFs when an electric current flows through coils under the plate of the cooker top…. heat is generated when the electromagnetic field reacts with the metallic pan on the plate…..the main issue is usually magnetic fields )….gas cookers are a safer alternative.

  • Harsha Vardhana R said,

    Thanks Lloyd,

    Under electric cooking, apart from MW and induction cooking, we have old style electric coils which can heat even a mud-pot. In India I have seen them since birth. Is it safer than Induction? Induction instruments need certain special plates, old-style just heats anything that touches it!

    I am moving towards a new residence with a kitchen, so I would like to have the safest cooking mode too! I am yet to purchase anything!

  • A. Gore said,

    Hi Lloyd, I love what you do and tell lots of people about your site. Re: your new video, I would send it on, but…. What do you mean when you say the ’embroyo ……is not conducive to ….radiation.’ That means it is not affected by it……..which is not the message you want to give? Also not happy with even the slightest encouragement here for me to put their phones so it is touching their heads. Your video suggests it is okay to do that……

    Otherwise I would be very happy to send it on, to many.

  • Michael Janko said,

    Hello Lloyd,
    I am a technophobe, so anything involving computers baffles me. I used to have Time Warner internet cable and an AT&T landline. I got fed up with the constant increase in prices, so I decided to try AT&T U-verse for my internet and phone. I emphasized to the salesperson and to the installer that I didn’t want wifi or anything with strong radiation. He installed a wire around my house so I supposedly wouldn’t need any wifi connection. Since installation I’ve been feeling worse when in the room with my computer and telephone. There is a tower for the U-verse with lights on for power, U-verse, phone 1, broadband, and service. There is a heavy rectangular object on the floor, probably the modem. When I disconnect the cord from the computer, it says that wifi is not available. I wonder if the wifi signal is still broadcasting. I have an electrical/radiation meter that I purchased at It registers at a high level next to any electrical device, but a couple of feet away the reading is way down. Any advice or suggestions?

  • Valerie said,

    Thanks Lloyd the list of definitions is a great help – I’ve got a long way to go but I will get there one step at a time.

    Regards Valerie

  • Keini said,

    Hi Lloyd. Thank you very much for all the information you are giving us. This list of definitions is very useful and will help me to make sense of all on this topic. Best wishes.

  • Hal said,

    To Linda’s comment – ceiling, heating coils. Recently had my girlfriend’s apartment swept for EMFs. Old building (50’s?) with ceiling coils. I’m with you Linda. The reading was shocking in numbers. Problem is, not so much her ceiling – turned off circuit breakers, don’t need heat in Los Angeles, but her floor, which is the ceiling of the tenants below. #s were off the hook. Not only does this design (augmented when electricity was cheap?) emit huge electric numbers from the ceiling of the apartment below her up into my girl’s place, but when the heat is turned on (winter L.A., am, etc.) it’s magnetism as well, the least common but most offensive field. I am severely EMF sensitive, just discovered after years of searching, and have been frying hard from the floor in my girl’s place for six years not knowing why until now. Linda, fortunately for you yours is a house with no one/field below you? Currently no one occupies the apartment beneath my girl so the landlady (a tolerant soul) turned off the breakers below. But when the apartment is re-rented it will be a deal breaker for my girl/us in her place unless the new tenant is as conscious of this plague and its consequences as we are. Fat chance. When the EMF reader guy we hired entered my girl’s apartment he looked around for air vents, saw none, saw the heater dial on the wall, and without knowing us or even getting out his meters yet, said, “you have to move”. Since the breakers below were turned off I stopped frying instantly. And I mean FRYING, sick as a dog from head to toe. Full blown headaches, ground pounding tinnitus, name the affliction, and yes the C word too. EMFs are beyond bad and, it appears, unfortunately cumulative. Electricity can be masked, aesthetics be damned, but not magnetism. God save us all.

  • Hal said,

    Hi Lloyd, thanks for great site. I’ve learned and continue to learn of this fascinating subject. I’ve recently discovered I’m electromagnetic sensitive and may have been accumulating in me and finally presented itself in the last year. I recently experienced a similar situation as Linda with ceiling heater coils and super high numbers in my old apartment bulding. Very challenging especially coming up from the floor from apartment below. I become physically ill and barely able to leave apartment in morning. Once I do, in ten minutes I’m considerably better and able to go to work. Any suggestions besides turning off circuit breakers? I’ve gotten landlady to turn them off in apartment below as it’s not occupied at the moment. I feel 1,000% better but dread the day a new tenant moves in downstairs. Any suggestions?

  • Cynthia said,

    Hi Lloyd,

    What do you think of radiant floor heatng? Is this different from what Hals talking about,or same?

    Thankyou for all the info.

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