Direct Energy, 2018a

Appendices 353
κ describes the ability of heat to ow, and it was introduced in Sec. 8.6.3.
Both of these ideas were discussed in the context of thermoelectric devices
because understandingthese devices requires the understandingof the ow
of both electrons and heat. Example values for electrical conductivity and
thermal conductivity are given in Table 8.4.
While not identical, the terms wave vector and wave function are worth
distinguishing. The term wave vector was introduced in Sec. 6.4 with the
idea of reciprocal space. Functions such as energy or charge density can be
described as varyingwith respect to position specied by the vector −→ r in
units of meters. These functions can also be described as varyingwith respect
to spatial frequency specied by the wave vector −→ k in units 1 m .Wave
function ψ was introduced in Section 11.7, and it is a fundamental idea of
quantum mechanics. The wave function is a measure of the probability of
ndingan electron or other quantity in a particular state.
Appendix D: Specic Energies
Table 14.4 lists the specic energy of various materials and devices. These
are representative values, not values for specic devices. Batteries by dierent
manufacturers, for example, will have a range of specic energy values,
and these values are often detailed in a datasheet. See the listed references
for additional information on the assumptions made. Two types of values
are listed for batteries. Both theoretical specic energy values for the chemical
reactions and specic energy values for practical devices. The notation
(th) indicates theoretical values while (pr) indicates practical values. NMH
is an abbreviation for Nickel Metal Hydride batteries.