The resistance of the wire at 20⁰C is 20 Ω and 500⁰C is 60 Ω. At which temperature its
resistance will be 25 Ω ?
(a) 50⁰C
(b) 60⁰C
(c) 70⁰C
(d) 80⁰C
Answers
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15
Answer:
(D) 80
Explanation:
WKT : R = R0 [ 1 + a( T2 - T1 ) ]
Here,
R=60
R0=20
T2=500
T1=20
Therefore 60 = 20 [ 1 + a( 500 - 20 ) ]
or a = [ (60/20) - 1 ] / 480 = 2 / 480 = 1 / 240
So, now for resistance R = 25
25 = 20 [ 1 + (1/240) *( T-20 ) ]
(where T is the new temperature (ans) )
or,
T = { [ (25/20) - 1 ] / (1/240) } + 20
T = 60 + 20
T = 80.
Correct?
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