Key Points

Our sense of touch cannot always reliably determine the hotness or coldness of a body. Different hands can perceive the same water as both warm and cool.

Temperature is a reliable measure of the hotness or coldness of a body. A hotter body possesses a higher temperature than a colder body.

A device specifically designed to measure temperature accurately is called a thermometer. It provides an objective reading of hotness or coldness.

There are two primary kinds of thermometers: clinical thermometers, which measure human body temperatures, and laboratory thermometers, used for various other purposes.

Clinical thermometers, often digital, are used to measure human body temperature. They generally use the Celsius scale, where the unit is degree Celsius ($^{\circ}\text{C}$).

The normal temperature of a healthy human body is considered to be $37.0^{\circ}\text{C}$ or $98.6^{\circ}\text{F}$. Individual temperatures may vary slightly from this average.

The three most-used scales of temperature are the Celsius scale (unit $^{\circ}\text{C}$), the Fahrenheit scale (unit $^{\circ}\text{F}$), and the Kelvin scale (unit $\text{K}$).

The SI unit for temperature is kelvin, denoted by $\text{K}$. Temperature in Kelvin scale can be converted from Celsius using the formula $\text{K} = {^{\circ}\text{C}} + 273.15$.

Always wash the thermometer tip with soap and water before and after use, reset it, and ensure the digital display portion is kept out of water while washing.

Laboratory thermometers typically have a wide temperature range, often from $-10^{\circ}\text{C}$ to $110^{\circ}\text{C}$. They are used for measuring temperatures of substances in experiments.

When measuring temperature with a laboratory thermometer, immerse its bulb fully without touching the bottom or sides of the container, hold it vertically, and read the temperature while it is still immersed.

Air temperature is a crucial weather parameter, with maximum and minimum temperatures monitored daily at weather stations globally. This data aids in making accurate weather forecasts.

Anna Mani (1918-2001) was an Indian scientist, known as the 'Weather Woman of India,' who developed numerous weather measurement instruments, significantly reducing India's dependence on foreign instruments.

The temperature of human beings does not normally fall below $35^{\circ}\text{C}$ or rise above $42^{\circ}\text{C}$. This narrow range is why clinical thermometers have a specific limited scale.

To read a thermometer accurately, it is essential to determine the smallest value each division represents. This is calculated by dividing the temperature difference between two bigger marks by the number of smaller divisions between them.