Determine the resistance and temperature-coefficient, Electrical Engineering

Determine the resistance and temperature-coefficient:

A platinum coil has a resistance of 3.146 Ω at 40oC and 3.767 Ω at 100oC. Determine the resistance at 0oC and the temperature-coefficient of resistance at 40oC.

Solution

Rt  = R0  + α0  R0  (t - t0 )

Take t0 = initial temperature = 0o.

Rt  = R0  + α0  t R0

= R0 (1 + α0 t )

R100 = R0 (1 + 100 α0) at          t = 100 C          ------- (i)

 

And        R40 = R0 (1 + 40 α0 )         at  t = 40oC           ----------  (ii)

From Eqs. (i) and (ii)

3.767 /3.146    = 1 + 100 α0/1 + 40 α0   ⇒ α = 0.00379 pero C

From Eq. (i)

∴ 3.767 = R0  (1 + 100 × 0.00379)

R0 = 2.732,

α40 =   1/( (1/ α0) + (t2  - t1 ) =1/ (1/0.00379) + (40 - 0) = 1/304 per  o C

Posted Date: 2/4/2013 3:07:39 AM | Location : United States







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