Question

A platinum RTD has a resistance of 100 ohms at 100°C. If the temperature coefficient is 0.004 / °C, what would be the change in resistance if the temperature rise is 50 °C?
1. 10 Ω
2. 15 Ω
3. 20 Ω
4. 25 Ω

Answer 1

Correct Answer - Option 3 : 20 Ω

Concept:

The resistance of the conductor changes when the temperature of that conductor changes.

New resistance is given by:

\({{R}_{t}}={{R}_{0}}\left( 1+α \text{ }\!\!Δ\!\!\text{ }T \right)\)

Where Rt = the resistance of the conductor after temperature changes

R0 = the resistance of the conductor before temperature changes

α = temperature coefficient

ΔT = final temperature – initial temperature

Calculation:

Given:

R_O = 100 ohm

α =  0.004 / °C

ΔT = 100°C - 50°C = 50°C

R_t = 100(1 + 0.004 x 50)

R_t = 120 ohm

So total change in resistance is: 

ΔR = 120 - 100 = 20 Ohm