Thermometer Reading Temperature, Kinds of Thermometers, Temperature Sensors in Thermometer (For CBSE, ICSE, IAS, NET, NRA 2022)

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Thermometer Reading Temperature

  • We come across objects that are hot or cold, in our day-to-day life.
  • On a hot summer day, we get relief from eating an ice cream and similarly in chilly winters from a cup of hot milk.
  • Sometimes, the need arises to find out how hot or how cold an object is, which we usually can find out by simply touching the objects.
  • Water at normal temperature appears hot when compared to the ice while it feels cold when compared to boiling water.
  • To find the exact measure of this hotness, the concept of temperature was introduced.


Thermometer Degree
  • Temperature is defined as the measure of the degree of hotness or coolness of an object. The device used for measuring temperature is called a thermometer.
  • Temperature was measured by a thermometer, when somebody in the family suffered from fever, the thermometers that measure body temperature is called clinical thermometer.
  • A thermometer looks like the one shown in the above figure.
  • It consists of a long narrow uniform tube made of glass. It has a bulb at one end which contains mercury.
  • Outside the bulb is a small shining thread of mercury.
  • When we rotate the mercury, we see two scales one with °C and the other with °F as the parameter.

What is a Normal Body Temperature?

  • Normal body temperature is about 98.6 degrees Fahrenheit or 37 degrees Celsius .
  • Normal temperature often varies from to ( to ) .
  • A normal temperature is Lower in the morning and increases during the day. It reaches its high in the late afternoon or evening.

Kinds of Thermometers

Kinds of Thermometers
  • Digital thermometers (best to use)
  • Glass (not recommended)
  • Fever strips (not recommended)

Temperature Sensors in Thermometer

  • The expansion of mercury due to heat is what tells us the temperature.
  • If we calculate the expansion of mercury per degree change in temperature; then we can calibrate the thermometers with a scale based on the expansion.
  • This is how a thermometer works. In honor of Fahrenheit՚s discovery, we have named the temperature scale after him.
  • The temperature sensors are so calibrated that the numbers on the thermometers represent the temperature of the body.
  • The Fahrenheit scale is used in the North America and a few other countries and the Celsius scale is used by the rest of the world. Below you will find the formulae for its conversion;

Reading a Thermometer


  • The thermometer is washed with water at normal temperature.
  • Check to see what type of thermometer you have.
  • Check the tip of a glass thermometer to make sure it is not broken or cracked. Do not use a broken or cracked thermometer.
  • Hold the thermometer at eye level with the numbers facing you.
  • It is given a few jerks. We notice that the jerks bring the level of mercury down. We make sure that it falls below the mark or the mark, the normal human body temperature.
  • The thermometer has then kept under the tongue or under the arms in order to get the reading on the thermometer.
  • Look for the numbers and measuring scale of black lines These vertical (up and down) lines stand for degrees of temperature. Most thermometers have two scales for temperature, Fahrenheit and Celsius. Read the numbers for (degrees of Fahrenheit) .
    • Each long line is for temperature.
    • The four shorter lines between each long line are for (two tenths) of a degree of temperature.

Thermometer Readings

Thermometer Readings
  • Look for the line of fluid running along between the numbers and the vertical black lines.
  • Read the number that is closest to where the column of fluid ends.

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