# What will happen to the reading if the bulb of a thermometer is suddenly introduced in a hot...

## Question:

What will happen to the reading if the bulb of a thermometer is suddenly introduced in a hot water bath?

## Thermal Expansion.

Most objects increase in volume when the temperature rises. Most liquids also have this same tendency. This physical phenomenon must be taken into account when designing oil pipelines due to their great length and environmental thermal changes.

If the bulb of a thermometer is quickly submerged in hot water, the volume of mercury will expand according to the following expression:

{eq}\Delta V = V_i\,\beta\,\Delta T {/eq}

Where: {eq}\Delta V {/eq} is the change in volume. {eq}V_i {/eq} is the initial volume. {eq}\beta {/eq} is the coefficient of volumetric expansion. {eq}\Delta T {/eq} is the change in temperature.

As can be seen from the above equation, the volume change of mercury is proportional to the temperature change and therefore the column of mercury indicating the temperature would rise rapidly to the temperature of the hot water bath. 