
body of the battery and enters the conductor wires through both terminals. For sim-
plicity, the energy current may be assumed to flow in at one end and its value is zero
at the other end.
2.2 Rate Of Radiation Loss Along Conductor Length.
Within the conductor,a photon may leave the body without being absorbed or it may
be absorbed by a lattice atom. It may be assume that, on average, a photon would
be absorbed after traveling a distance of d. As the lattice spacing of solids is in the
order of 1Å, we may make a wild guess of d = 500Å. If a photon is absorbed, the
direction in which another photon would be emitted may be assumed to be random.
If a photon is absorbed at the conductor surface, the probability that it would leave
the conductor is about 0.5. For photons within a distance of d from the surface, the
probability may be α < 0.5. For a cylindrical wire of radius r, the probability that a
photon is within the surface d layer is about 2d/r. So the probability p that a photon
would leave the conductor body is: p = 2αd/r. For aluminum core steel-reinforced
high power transmission line, the radius may be 5cm. Assuming α = 0.3, d = 500Å,
the probability is:p = 2 ∗ 0.3 ∗ 500/10
10
/0.05 = 6 × 10
−7
. The observation is that
most photons deeper within the conductor would be absorbed and re-emitted by the
lattice atoms without leaving the conductor body.
If we trace the photon transmission path,the speed of transmission would be near
light speed, but less, if it is assumed there is a delay in absorption/re-emission. If it is
assumed the direction of re-emission is random, then the path of transmission takes
on the typical characteristic of a random walk. The nodes of the path would have the
greatest probability to be near the origin of transmission based on the normal distri-
bution.
Initiallywhenthe source photonsentersone end ofthe conductor,the photon den-
sity would be greatest at the source end and it decreases along the conductor length as
some power is loss due to surface radiation loss; the energy current would thus lose
intensity along the conductor length. If it is assumed that the conductor has achieved
a steady uniform temperature, then the rate of power loss per unit length is uniform
along the conductor’s length as the rate of radiation is a function of its surface temper-
ature. Thus, the radiation loss is uniform along the conductor’s length. As the rate of
radiation loss is equal to
∆v
∆x
i, the rate of voltage drop along the conductor’s length is
also uniform.
Assuming a steady uniform conductor temperature,there is now the following ob-
servations for a current-carrying conductor with auniform cross-section and ofhomo-
geneous material:
1. the radiation loss per unit length of conductor is constant.
7