132
CHAPTER 18
18.55
(a) For the first measurement, the equivalent circuit is
as shown in Figure 1. From this,
1
2
ab
yy
y
RRRR R
==+=
so
1
1
2
y
RR
=
(1)
For the second measurement, the equivalent circuit
is shown in Figure 2. This gives
2
1
2
ac
y
x
RR RR
==
+
(2)
Substitute (1) into (2) to obtain
21
11
22
x
R
=+
, or
1
4
x
R
=−
(b) If
R
, then
12
13
and
6.0
R
=Ω
= Ω
2.8
x
R
=
Ω
Since this exceeds the limit of 2.0
Ω
, the antenna is
inadequately grounded .
18.56
Assume a set of currents as shown in the circuit
diagram at the right. Applying Kirchhoff’s loop
rule to the leftmost loop gives
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This document was uploaded on 10/20/2011.
 Spring '09
 Physics, Current, Work

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