Why thermometer can measure temperature

People often judge how hot or cold things are based on their feelings, but such judgments are usually inaccurate due to the existence of many factors. If you want to know the true temperature of an object accurately, you need a thermometer.

The earliest manufacturer of the thermometer was the Italian scientist Galileo. Galileo made a glass tube with a spherical end and air in the middle, and the other end of the tube was placed in the liquid with the opening facing down. When the temperature rises, the air in the tube expands due to heat. Under the same conditions, the thermal expansion of the liquid is not as great as the gas, so the height of the liquid level in the tube will be reduced. Similarly, when the temperature decreases, the liquid level in the tube will rise, but such a thermometer is not very accurate due to the influence of atmospheric pressure changes.

The thermometer we are using now is made entirely by the principle of thermal expansion and contraction of liquid: under the same conditions, the thermal expansion of liquid is greater than that of solid, so when the temperature changes, the liquid level in the glass tube Rise or fall; and because the inner diameter of the glass tube of the thermometer is very thin, the liquid volume change shows a significant height change in the thin tube, so the specific value of the temperature can be read from the scale on the glass tube. The liquid in the thermometer is generally mercury, kerosene and alcohol.