Question

A Resistance of R of thermal coefficient of resistivity α(alpha) is connected in parallel with a resistance 3R having thermal coefficient of resistivity 2α(2alpha).Equivalent thermal coefficient or resistivity for the combination is
1. 7α/4 2. 5α/4
3. 9α/4 4.3α/2

Answer 1

Explanation:

equivalent thermal coefficient in parallel is( a2R1+a1R2)/(R1+R2)

=(2aR+3aR)/(R+3R)

=5a/4

ans is option 2

Answer 2

Answer:

option (2)

Explanation:

The equivalent resistance at 0°C is

$\sf \dfrac{R_{10} R_{20}}{R_{10}+R_{20}}$

The equivalent resistance at t°C is

$\sf \dfrac{R_{1}R_{2}}{R_{1}+R_{2}}$

$\sf R_1 = R_{10} (1+α t)$

$\sf R_2 = R_{20} (1+2α t)$

$\sf R = R_{0} (1+α_{eff} t)$

$\sf \alpha_{eff}=\dfrac{5}{4} α$