Question

The temperature coefficient of resistance for carbon at 0C is -0.0048/C. What is the significance of the minus sign? A carbon resistor has a resistance of 500Ω. Determine its resistance at 50C

Answer 1

Given:

The temperature coefficient of resistance for carbon at 0°C is -0.0048/°C. A carbon resistor has a resistance of 500Ω.

To Find:

What is the significance of the minus sign?  Determine its resistance at 50°C.

Solution:

Meaning of negative sign of coefficient of resistance is that value of resistance decrease with increase in temperature.

$\mathbf{Coefficient\ of\ resistance=\alpha =-0.0048 \ \ \ per\ degree\ centigerate}$

$\mathbf{Resistance\ at\ zero\ degree\ centigerate=R_{0} =500 \\ \ \Omega }$

$\mathbf{Resistance\ at\ 50\ degree\ centigerate=R_{50} =Unknown }$

We know the formula of resistance at different temperature:

$\mathbf{R_{t}=R_{0}(1+\alpha \times t) }$

On putting respective value in above equation:

$\mathbf{R_{50}=500\times (1-0.0048 \times 50) }$

$\mathbf{R_{50}=380 \ \ \Omega }$

Means resistance of carbon at 50°C is 380Ω.

Answer 2

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Means resistance of carbon at 50°C is 380Ω