# What electricity really is

I purely by chance read something on quora digest that electricity isn't the flow of electrons but photons that are ejected from free electrons then re absorbed by another free electron this process makes them vibrate  and move forward a fraction of an inch. Now I know there was a discussion  about this on here a while back so what was the final conclussion. I know its a tough subject ide like to get my head round it of course its made harder because I can't understand the maths.

Parents
• A couple of questions on that theory:

• Where do the electrons get enough energy to release a photon?  Imagine a copper wire sitting in a bath of liquid nitrogen, connected to a supply of <1 volt.  There's very little energy to excite the electrons, so that they can then release photons.
• How do the electrons know which way to emit the photons?  If it's random, then there will be no overall current.
• You won't find it in any commonly accepted standard text. Such an assumption is neither necessary nor desirable as a part of the standard model of electromagnetic theory.

Mike.

(I am, originally by training at least, a physicist, although an experimental one, rather than a theoretician , so in the eyes of some an engineer/2)

• The problem physicists have is electromagnetic power/energy is massless so cannot be weighed or measured apart from equivalents in retrospect which are not 3D. Time in frequency is measured alright But they should be able to find the shape of a volume of EM energy I am hoping??

• Can The shape of a volume of (EM) energy not already be determined using various existing methods ?

• The problem physicists have is electromagnetic power/energy is massless

If e = mc², them m = e/c².

• We electrical engineers know that power/energy must be balanced or a Cosine reduction in power and appearance of quantum Var's is witnessed.

If a physics formula of electromagnetic light energy does not have a Cosine or more correctly a Sine symbol then it cannot correctly describe a 3D volume unit of density.

• Could you elaborate on what is meant by ‘quantum Vars’ this isn’t a standard term as far as I am aware. Is this some crossover into quantum mechanics ?

• Quantum electro dynamics I think is just physicists way of explain  imaginary VARs in 2 directions only.

• So what ? yes of course it does - its not a problem for physicists, more for folk who do not understand what physics is or how to use it  to describe reality. In general the change in mass of something when it acquires terrestrial thermo-chemical  sort of energies is negligible,  The change in mass of my car when parked in the drive compared to the higher mass when pelting down the M3 or similar is utterly dwarfed the change in mass due to the thermal change in its volume altering the amount of air inside, the steady addition or subtraction of odd dust particles, dead flies on the grill, mud on the tyres or whatever.

Consider a car with a rest mass of 1 tonne (1000kilos) , Now let us move it at 30m/sec (3600 sec per hour) 96km per hour, nearer to 60 mph than 70, honestly officer.

Energy is 1/2.m*v^2 = 500,000*30*30 = 450MJ

Mass change is E/c^2 = 0.000000005 kg = 0.005 milii-grams >  about 1% of the weight of ink in a single printed full stop.

It only starts to noticeably increase the mass  (making it harder to accelerate) when the speed of the car gets to about 1% of 'c' which would really be going some, even for Mrs MAPJ1 driving.

Mike.

• Good thinking Mike, have you ever tried to work out the difference in weight of a 12 volt battery  flat to full charge and its affect on specific gravity ??

• Well there are several changes in a car battery between flat (2 lead plates and some acid) and charged. Not least the formation of  lead oxide on the positive plate, changes in electrolyte density and so on.  There is of course an energy related  change in mass in terms of how that battery accelerates due to a given force, or indeed if the battery were in outer space and attracting smaller items to orbit around it, but again like the car, practically this is utterly dwarfed by the (in)accuracy to which you can measure the weight of the thing in the first place and then correctly discount all the other effects.

The only time I have ever really had to consider relativity for real was for part of some medical kit that was designed for accelerating protons. In that the drift tubes between the RF resonator cavities had to allow for the 'speed limit' and did not get shorter at the high energy end of the machine quite as fast (as the protons di not get quite as fast) as normal Newtonian mechanics might have predicted. Even then just using special (Lorenz contraction) relativity was quite enough precision.

Most of the time, all the relativity and QED  stuff is a diddy correction on traditional mechanics and EM. Normal quantum mechanics however you rely upon  every time you operate a transistor - and there are millions of those in many of the 'chips' in the device you use to read this forum. (the non mathematical holes and electrons model gets you a long way with qualitative arm waving explanations, but to actually design new semiconductor devices rather than just to use ones made by others, and to accurately understand & predict behaviour of band gaps at junctions etc, sadly, needs the full maths, -which is where I usually find myself deferring to a colleague ..)

Mike