Question

Resistance of the wire is measured as $2 \,\Omega$ and $3\, \Omega$ at $10^{\circ} C$ and $30^{\circ} C$ respectively. Temperature $co -$ coefficient of resistance of the material of the wire is :

• A. $0.033^{\circ} C ^{-1}$
• B. $-0.033^{\circ} C ^{-1}$
• C. $0.011^{\circ} C ^{-1}$
• D. $0.055^{\circ} C ^{-1}$

Answer 1

Answer: (A)

$R = R _{0}(1+\alpha \Delta T )$
$3= R _{0}(1+\alpha(30-0))$
$2= R _{0}(1+\alpha(10-0))$
$\frac{3}{2}=\frac{1+30 \alpha}{1+10 \alpha}$
$\alpha=\frac{1}{30}=0.033$