Question

Resistance of tungsten wire at ${150}^o$C is $133\Omega$. Its resistance temperature coefficient is $0.0045{/}^o$C. The resistance of this wire at ${500}^o$C will be?

• A. $180\Omega$
• B. $225\Omega$
• C. $258.8\Omega$
• D. $317\Omega$

Answer 1

The correct option is C $258.8\Omega$

$\frac{R_t}{R_t}=\frac{1+\propto t}{1+\propto t}$

$\frac{133}{R_t}=\frac{1+0.0045\left(150\right)}{1+0.0045\left(500\right)}$

$\frac{133}{R_t}=\frac{1+0.675}{1+2.25}$

$\frac{133}{R_t}=\frac{1.67}{3.25}$

$R_t=\frac{3.25\times 133}{1.67}=\frac{432.25}{1.67}$$=258.8\Omega$