The resistance of a field coil measures 50Ω at 20ºC and 65Ω at 70ºC. The temperature coefficient of resistance is

Question

The resistance of a field coil measures 50Ω at 20ºC and 65Ω at 70ºC. The temperature coefficient of resistance is (A) 0.0086/ºC (B) 0.0068/ºC (C) 0.0096/ºC (D) 0.0999/ºC

Tardigrade Admin · Accepted Answer

The value of temperature coefficient of resistance is given by α=(R2-R1/R1(t2-t1))=(65-50/50(70-20)) (t1 and t2 are in Â°C) ⇒ α=(15/50Ã50)=0.006/Â°C

Q. The resistance of a field coil measures 50 $Ω$ at 20ºC and 65 $Ω$ at 70ºC. The temperature coefficient of resistance is

0.0086/ºC

0.0068/ºC

0.0096/ºC

0.0999/ºC

The value of temperature coefficient of resistance is given by
$α = \frac{R _{2} - R _{1}}{R _{1} ( t _{2} - t _{1} )} = \frac{65 - 50}{50 ( 70 - 20 )}$
$(t_{1}$ and $t_{2}$ are in °C)
$\Rightarrow α = \frac{15}{50 \times 50} = 0.006/° C$

Q. The resistance of a field coil measures 50Ω at 20ºC and 65Ω at 70ºC. The temperature coefficient of resistance is