Question

The resistance of a field coil measures 50$\Omega$ at 20?C and 65$\Omega$ at 70?C. The temperature coefficient of resistance is

• A. 0.0086/?C
• B. 0.0068/?C
• C. 0.0096/?C
• D. 0.0999/?C

Answer 1

Answer: (B)

0.0068/?C

Answer 2

The value of temperature coefficient of resistance is given by
$\alpha=\frac{R_2-R_1}{R_1(t_2-t_1)}=\frac{65-50}{50(70-20)}$
$(t_1$ and $t_2$ are in ?C)
$\Rightarrow \alpha=\frac{15}{50?50}=0.006/?C$