Is power lost in a circuit always lost as heat?

[Nirios]

A simple thought experiment could provide an analogy. Imagine water in a long closed pipe with a piston at the end, and imagine this piston is connected to a paddle on the surface of a lake. If you move the water back and forth in the pipe in an oscillating manner the piston at the end will move back and forth with the water pressure, which will move the paddle in the lake. The paddle moving in the lake will generate waves in the water that will radiate outwards and carry energy away. No water is actually flowing in this example, neither flowing out of the pipe, nor flowing away from the paddle (waves move through water, but the water stays where it is).

It follows that you will have to do work moving the water back and forth in the pipe to provide the energy to move the paddle in the water and generate the waves. We could say that the water in the pipe is coupled to the paddle.

There is a similar kind of situation with electromagnetic radiation. The charged electrons moving back and forth in the antenna generate moving electric and magnetic fields, which couple together to form electromagnetic waves carrying energy away from the antenna. By analogy with the water example, you have to do work moving the electrons back and forth to provide the energy carried away by the waves.

I know almost nothing about RF and that is one of the best analogies I've heard/read for antennas.

So when does your online RF class start??  I'll be the first to signup. 

[ResR]

I have an Ectaco Takser-E (Made in Estonia) used as a tabletop clock, 1995 era distance reader for power meters. It works fine, but it fills empty FM/AM/SW frequencies with constant noise of 50Hz modulated ~600Hz sound with 2Hz clipping. So sometimes energy is lost as RF energy.
http://sphotos-e.ak.fbcdn.net/hphotos-ak-prn1/45023_406002672812512_718706042_n.jpg
I connected Schurter 5110.1033.1 with X-rated 0,1uF 275VAC capacitor soldered to output of the filter to mains cable as close to the device as possible and it didn't had any effect so the device itself transmits the RF energy.
(Also it gets warm and heats up anything that is placed on it to 30...35°C)

[4to20Milliamps]

More stuff to ponder:

Attenuation and absorption

http://en.wikipedia.org/wiki/Attenuation

http://en.wikipedia.org/wiki/Absorption_(electromagnetic_radiation)

[CarlG]

Sorry, really of topic, but...

.... exceeding the speed of light. 

There's nothing strange about exceeding the speed of light. E.g. there is Cherenkov radiation, which is emitted when a particle moves in a medium at a speed faster than the speed of light in that medium. Well known in particle physics, Cherenkov radiation is used as part of event detection mechanisms.

Also, if I remember correctly, in RF transmission lines, you can have a (reactive) wave front propagating faster than the speed of light (in vacuum), created ar the intersection of two superimposed waves. I'm no expert in RF so I may have got it wrong, but that's basically how it was explained in some class att the university.

It's only the speed of light in vacuum that is a definite barrier for an object with a mass;)

[nukie]

Is sound a product if rf energy? Humming is also power lost.

[ignator]

Sorry, really of topic, but...

.... exceeding the speed of light. 

There's nothing strange about exceeding the speed of light. E.g. there is Cherenkov radiation, which is emitted when a particle moves in a medium at a speed faster than the speed of light in that medium. Well known in particle physics, Cherenkov radiation is used as part of event detection mechanisms.

Also, if I remember correctly, in RF transmission lines, you can have a (reactive) wave front propagating faster than the speed of light (in vacuum), created ar the intersection of two superimposed waves. I'm no expert in RF so I may have got it wrong, but that's basically how it was explained in some class att the university.

It's only the speed of light in vacuum that is a definite barrier for an object with a mass;)

To quote wikipedia "Cherenkov radiation results when a charged particle, most commonly an electron, travels through a dielectric (electrically polarizable) medium with a speed greater than that at which light would otherwise propagate in the same medium".
Cherenkov radiation does  not exceed the speed of light, it occurs when an electron (in this case) traveling in a medium (in this case water), and the electron exceeds the phase velocity  of light in the medium, the phase velocity is  comparing their two speeds, light in water is .75c (1.33 is index of refraction for water, the recipical is the relative speed decrease of the light in water), and the electrons are moving typically at .95c, this radiation is energy caused by the electrons motion through the medium.  As the electron is loosing energy, it's velocity is decreasing (this keeps this germane to this thread), and this light absorbed is energy, and results in heat.