Digital Signal Processing Reference
In-Depth Information
2-6
Assume that two infinitely long parallel wires are separated by a distance
of 5 in. with currents that are equal but opposite. Find the current if the
force per unit length is 0.25 N/m.
2-7
Determine the energy needed to assemble three point charges in free space
from infinity to the following (
x
,
y
,
z
) coordinates: (0,0,0), (1mm, 0, 0),
(
1 mm, 0, 0).
2-8
For a parallel-plate capacitor in free space
(ε
r
=
−
1
)
with total change
Q
on one plate and—
Q
on the other with plate areas of
A
separated by
the distance
d
, calculate the external force required to keep the plates
stationary.
2-9
If a plane wave is propagating in the
z
-direction in free space and it
impinges on a planar dielectric medium where
ε
r
=
9
.
6, how much of the
wave is propagated? How much is reflected? If the electric field incident
on the boundary has a value of 60 V/m, how much power is carried in the
initial wave? How much power is reflected and transmitted? Show that
power is conserved.
E
=
br
3
2-10
If the electric field in an area of space is known to be
a
r
(where
b
is a constant) in spherical coordinates, find the charge density
ρ
and the
total charge within a sphere of diameter
d
.
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