Temperature Scales

Temperature Scales

1. Celsius scale:The lower and upper fixed points are 0⁰C and 100⁰C.  The fundamental interval is divided into 100 equal parts.
2. Fahrenheit scale:The lower  and upper fixed points are 32⁰F and 212⁰F.  The fundamental interval is divided into 180 equal parts.
3. Absolute scale/Thermodynamic scale:The lower and upper fixed points are 273k and 373k.  The fundamental interval is divided into 100 equal parts.

The absolute scale of temperature is thermodynamic scale because it gives us the idea of the lowest possible temperature or absolute zero with the value of –273⁰C.

−273oC=ok=273k

The absolute zero is the lowest possible temperature below which nothing can be cooled since temperature is the measure of the average or mean kinetic energy of the molecules of a substance.  It follows that as we subtract heat from a substance, its temperature drops and hence its kinetic energy until it eventually becomes zero under which the molecules remain stationary.

To convert from one scale to another, use interpolation technique.

Unknown temperature – Lower fixed pointUpper fixed point – Lower fixed point=Known temperature – Lower fixed pointUpper fixed point – Lower fixed point20−0100−0=θ−32212−32θ−32=20×180100=36θ−32=36θ=36+32=68oF