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564
Temperature
P19.54
The angle of bending
θ
, between tangents to the two ends of the strip, is
equal to the angle the strip subtends at its center of curvature. (The angles
are equal because their sides are perpendicular, right side to the right side
and left side to left side.)
(a)
The definition of radian measure gives
LL
r
i
+=
∆
11
and
r
i
∆
22
By subtraction,
∆∆
r
r
21 2
1
−=−
bg
ααθ
αα
21
LT
r
r
ii
i
∆
∆
∆
−=
=
−
FIG. P19.54
(b)
In the expression from part (a),
is directly proportional to
∆
T
and also to
−
.
Therefore
is zero when either of these quantities becomes zero.
(c)
The material that expands more when heated contracts more when cooled, so the bimetallic
strip bends the other way. It is fun to demonstrate this with liquid nitrogen.
(d)
π
=
−
=
×−
×°
°
=×
°
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .
 Fall '11
 Staff
 Physics

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