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WBJEE 2017 Physics Solved Paper
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© examsnet.com
Question : 16
Total: 40
Consider the circuit shown in the figure. The value of the resistance X for which the thermal power generated in it ispractically independent of small variation of its resistance is
X
=
R
X
=
R
3
R
2
X
=
2
R
Validate
Solution:
i
=
E
(
R
+
R
x
R
+
x
)
V
R
x
=
E
R
x
R
+
x
(
R
+
R
x
R
+
x
)
=
E
x
(
R
+
2
x
)
P
x
=
V
R
x
2
x
=
E
2
x
(
R
+
2
x
)
2
d
P
x
d
x
=
E
2
(
R
−
2
x
)
(
R
+
2
x
)
3
⇒
d
P
x
=
E
2
(
R
−
2
x
)
(
R
+
2
x
)
3
d
x
(
d
P
x
)
wil be zero for all (dx) if
x
=
R
2
© examsnet.com
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