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5.2
Looking at the 4 terms in more detail
(1) The net number of particles j flowing out of the volume
∆
V :
dA
j
j,E,
d
d d
N
E
Ω
= Φ Ω
at the surface element dA:
∆
V
∆
S
j,in-out
j,E,
d
d d d
N
A E
Ω
= ΩΦ Ω
ur
ur
j,in-out
j,E,
d
d
d d d
S
N
A E
Ω
= ΩΦ Ω
∫
ur
ur
over the entire surface:
31