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88
CHAPTER 17
Thus,
()
28
any combination of length and diameter satisfying the relation
4.8
10
m
d
−
=×
l
1.0 m
=
l
will
be suitable. A typical combination might be
and
82
4
4.8
10
m
2.2
10
m
0.22 mm
d
−−
=
×
=
Yes
3
cm
() ( )
, such heating elements could easily be made from less than 0.5
of Nichrome.
The volume of material required for the typical wire given above is
63
2
24
7
3
3
10 cm
2.2
10
m
1.0 m
1.5
10
m
0.15 cm
1 m
VA
d
ππ
==
=
×
= ×
=
ll
3
17.47
The energy that must be added to the water is
6
J1
k
W
h
200 kg
4 186
80 C
15 C
15 kWh
kg
C
3.60
10 J
Em
cT
=∆
=
°
−
°
=
⋅°
×
and the cost is
( )
15 kWh
$0.080 kWh
$1.2
t
E rate

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