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Mechanical Properties Of Fluids

Question
CBSEENPH11020332

Two conductors have the same resistance a 0°C but their temperature coefficients o resistance are α1 and α2. The respective temperature coefficients of their series parallel combinations are nearly

  • fraction numerator straight alpha subscript 1 space plus straight alpha subscript 2 over denominator 2 end fraction comma space fraction numerator straight alpha subscript 1 space plus space straight alpha subscript 2 over denominator 2 end fraction
  • fraction numerator straight alpha subscript 1 space plus straight alpha subscript 2 over denominator 2 end fraction comma space straight alpha subscript 1 space plus straight alpha subscript 2
  • space straight alpha subscript 1 space plus straight alpha subscript 2 comma space fraction numerator straight alpha subscript 1 space plus straight alpha subscript 2 over denominator 2 end fraction
  • straight alpha subscript 1 space plus straight alpha subscript 2 space comma space fraction numerator straight alpha subscript 1 straight alpha subscript 2 over denominator straight alpha subscript 1 space plus straight alpha subscript 2 end fraction

Solution

A.

fraction numerator straight alpha subscript 1 space plus straight alpha subscript 2 over denominator 2 end fraction comma space fraction numerator straight alpha subscript 1 space plus space straight alpha subscript 2 over denominator 2 end fraction

Re = Ro +Ro
2R(1 + αsΔT)
= R( 1 +α1ΔT) + R(1+α2ΔT)
= αs = α12 / 2
Rp = R x R / R+R
straight R over 2 left parenthesis space 1 space plus space straight alpha subscript straight p increment straight T right parenthesis space equals space fraction numerator straight R space left parenthesis 1 space plus straight alpha subscript 1 increment straight T right parenthesis space straight x space straight R left parenthesis space 1 space plus space straight alpha subscript 2 increment straight T right parenthesis over denominator straight R space left parenthesis 1 space plus straight alpha subscript 1 increment straight T right parenthesis space plus space straight R left parenthesis space 1 space plus space straight alpha subscript 2 increment straight T right parenthesis end fraction
fraction numerator begin display style 1 space plus space straight alpha subscript straight p increment straight T end style over denominator 2 end fraction space equals space open parentheses 1 space plus space straight alpha subscript 1 increment straight T close parentheses left parenthesis 1 space plus space straight alpha subscript 2 increment straight T right parenthesis
space space space space space space space space space space space space space space space space space space space space space space space space space space left square bracket space 1 space plus space left parenthesis straight alpha subscript 1 space plus space straight alpha subscript 2 right parenthesis increment straight T right square bracket to the power of negative 1 end exponent
space equals space left square bracket 1 space plus space left parenthesis straight alpha subscript 1 space plus straight alpha subscript 2 right parenthesis increment straight T right square bracket space left square bracket 2 space plus space open parentheses straight alpha subscript 1 space plus space straight alpha subscript 2 right parenthesis increment straight T close parentheses to the power of negative 1 end exponent
space equals space 1 half space left square bracket space 1 space plus space left parenthesis straight alpha subscript 1 space plus space straight alpha subscript 2 right parenthesis space increment straight T right square bracket space open square brackets 1 minus fraction numerator left parenthesis straight alpha subscript 1 space plus space straight alpha subscript 2 right parenthesis over denominator 2 end fraction increment straight T close square brackets
fraction numerator 1 space plus space straight alpha subscript straight p increment straight T over denominator 2 end fraction space equals space open square brackets 1 plus fraction numerator begin display style left parenthesis straight alpha subscript 1 space plus space straight alpha subscript 2 right parenthesis end style over denominator begin display style 2 end style end fraction increment straight T close square brackets
straight alpha subscript straight p space equals space fraction numerator straight alpha subscript 1 space plus straight alpha subscript 2 over denominator 2 end fraction