Content Curator
Theremometer is a universal device that is used to measure temperature. As we all know, temperature is the unit to measure heat. Temperature can be measured using units, like Celsius (˚C), Kelvin (K), and Fahrenheit (˚F). Depending on the type of usage, thermometers are classified into various types from clinical thermometers to digital laboratory thermometers. Thermometers are used extensively in laboratories for research purposes, by doctors to monitor the body temperature of patients, for cooking and even in automobile industries.
Also Read: Temperature formula
| Table of Content |
Key Terms: Thermometer, Clinical Thermometer, Mercury, Thermocouple, Celsius, Kelvin, Heat, Celsius, Fahrenheit
What is a Thermometer?
[Click Here for Sample Questions]
A thermometer is a device that is used to measure temperature. Temperature can be defined as a measurable extent of either hotness or coldness. In fact, it can be expressed as a mathematical representation of heat. The different units to measure temperatures are Celsius (˚C), Kelvin (K), and Fahrenheit (˚F).
- Thermometers are devices that detects temperature or the temperature difference (the degree of hotness or coldness of an object).
- Thermometers are frequently used to monitor processes in technology and industry, as well as in meteorology, medicine, and scientific study.
A thermometer contains two essential components:
- Temperature Sensors
- Graduated Scale
Temperature Sensor
It records the changes in temperature. For example, the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer
Graduated Scale
It consists of numerical values which are expressed in degrees Celsius, Fahrenheit or Kelvin. For example we can see a scale that is marked on a mercury-in-glass thermometer or the digital readout on an infrared model.
Clinical Mercury Thermometer
Read More:
Uses of Thermometer
[Click Here for Previous Year Questions]
A thermometer's primary function is to measure the temperature of a body, object, surroundings or atmosphere. The following are some examples of thermometer applications and uses:
- Domestic purposes
- Laboratory purposes
- In automobiles
- In industries
- In restaurants
Thermometers for Domestic Purpose
- Thermometers are used to check the temperature of water before bathing.
- It is also used to check the temperature of food items for cooking.
- Temperature of grill stands, ovens, and other heating appliances can also be checked using thermometer to avoid accidents and burns.
Thermometer for Laboratory Purpose
- Thermometers are used widely for research purpose in laboratories.
- It is used to mark the temperature of a solution.
- It is also used to measure atmospheric or room temperature to carry out experiments.
Uses of Thermometers in Automobiles
- Infrared thermometers can measure the temperature of cables, hoses, or other equipment for car repair and service enhancements.
- It is also used for measuring the temperatures of various car parts such as tyres, under the hood, engines, transmission, brakes, and clutches, etc.
Uses of Thermometers in Industries
- Checking for air leaks and inadequately insulated areas is important in various industries to verify safety standards.
- The requirement for insulation can be determined by measuring the temperature of the inner and outer surfaces of the walls and if the difference is high, the walls require suitable insulation.
Thermometers are used in Restaurants
- Big restaurants use thermometers to monitor the temperature of the oil and the dishes for cooking and baking.
- Simply testing the sample with an infrared thermometer will give the results of the entire batch.
- Thermometers verify that semi-solid dishes have achieved the desired temperature, which kills any microorganisms present.
Frequently Asked QuestionsQues. “Mercury a good choice for thermometer.” State reason. (3 marks) Ans. Mercury can be found in liquid state at room temperature and typically comes with the highest expansion coefficient. Therefore, even the slightest temperature change is assumed significant. Likewise, mercury’s boiling point makes it suitable for the measurement of higher temperatures. One of the other reasons why mercury is used in thermometers is mainly because it does not stick to the surface of the glass and also similarly has a shiny appearance. Ques. Whhy are clinical thermometers mostly replaced today with digital thermometers? (1 mark) Ans. One of the main reasons why clinical thermometers are being replaced with digital thermometers is because mercury is a very toxic element. Hence, these thermometers are now replaced by digital thermometers. |
Types of Thermometer
[Click Here for Sample Questions]
The following are the most common thermometer types:
Clinical and Medical Thermometer
- Body temperature is measured with a clinical thermometer.
- Clinical thermometers consist of a glass tube filled with mercury which expands when temperature increases.
- The level at which mercury stops is marked against a graduated Celsius or Fahrenheit scale.
- The majority of thermometers manufactured in the twentieth century are mercury thermometers.
- They are sensitive and precise.
- These thermometers are also known as doctor's thermometers since they are used in clinics by doctors.
- It is used to determine the temperature of a person's body in the range of 35 °C to 42 °C.
- Medical thermometers are cleaned with alcohol before and after each use.
Laboratory thermometers
- For experimental purposes, laboratory thermometers are used to determine the room temperature of heated solids and liquids.
- It detects temperatures between 5 and 110 degrees Celsius, as well as greater temperatures.
Digital thermometers
- Digital thermometers use an electrical circuit to measure temperature.
- They send the data they collect to a microprocessor, which analyses it and displays it numerically on a digital screen.
- They are simple to operate, quick, precise, and affordable.
- Digital thermometers are high-precision thermometers that are used to measure the temperature of a body.
Infrared Ear thermometers
- Body heat is measured in the form of infrared energy emitted by a heat source using infrared thermometers.
- The tympanic membrane temperature, or eardrum temperature, is the temperature in the ear.
- This is one of the methods for taking your body temperature through your ear.
- This method of taking temperature is preferred for children.
- In adults, the typical ear temperature is 99.5 degrees Fahrenheit (37.5 degrees Celsius).
- Infrared ear thermometers should not be over-squeezed or used on ears that are too waxy.
Mercury thermometers
- It has a temperature range of -35°C to +500°C and has a linear expansion property (with compressed nitrogen).
- This type of thermometer takes longer to read the temperature than the others, and the reading is frequently more challenging, particularly for the elderly or visually handicapped.
Alcohol in Glass thermometers
- It is made of sealed glass and shows the temperature on a graduated scale by the level at which mercury or alcohol reaches.
- Temperature variations cause these liquids to dilate and contract.
- These thermometers now incorporate coloured alcohol because of the risk of mercury contact.
Platinum Resistance Thermometers
- These take temperature readings using a platinum wire connected to an electrical resistance that changes with temperature.
- It is commonly used to measure outside temperatures and is extremely accurate, though slow.
- The resistance of the material in these thermometers increases in direct proportion to the increase in temperature. It detects temperatures between 500 K and 2300 K.
Thermocouple Thermometers
- These thermometers are commonly used in laboratories to swiftly measure temperature.
- They measure temperature by using an electrical resistance.
- This resistance provides a voltage that fluctuates depending on the temperature of the connection.
Plastic Strip Thermometer
- Plastic strip thermometers are used to detect the temperature of a child’s body.
- Certain plastic strips attached to a baby's forehead can assess temperature changes in real-time by providing a colourimetric scale that tells us if a child has a fever or not.
- However, such a measurement is only indicative and not accurate.
Types of Thermometer
Read More:
Things to Remember
- A thermometer is a device that is used to measure temperature.
- The thermometer comprises a small glass tube with a thin liquid column that rises and lowers in response to temperature changes.
- Thermometers are frequently used to monitor scientific processes in laboratories.
- Body temperature is measured with a medical or clinical thermometer.
- Laboratory thermometer is used to determine the room temperature of heated solids and liquids.
- Infrared thermometers can take readings from a distance.
- Restaurants use thermometers to monitor the temperature of the dishes for baking and cooking.
Previous Year Questions
Sample Questions
Ques: What is the purpose of the kink in a mercury clinical thermometer? (1 Mark)
Ans: The kink in the mercury clinical thermometer is used to prevent the mercury from flowing back to the bulb before taking the reading in the temperature.
Ques: State the limitation of clinical thermometer. (1 Mark)
Ans: The clinical thermometer cannot measure the temperature of more than 42°C.
If it is kept in the sun or near a flame, then it can break.
Ques: How can we measure the temperature of other objects rather than the human body? (1 Mark)
Ans: Temperature of other objects can be measured with laboratory thermometer because clinical thermometer cannot give readings above than 42°C.
Ques: You may have noticed that a few sharp jerks are given to the clinical thermometer before using it. Why is it done so? (1 Mark)
Ans: Jerks are given to a clinical thermometer before using it, so that the mercury level settles down below normal temperature. It will help in measuring the accurate temperature of the body.
Ques: Write the advantages of an alcohol thermometer over a mercury thermometer. (2 Marks)
Ans: The advantages of alcohol thermometer over mercury thermometer are as follows:
- Alcohol thermometers are cheaper than mercury thermometers.
- They are less harmful.
- Alcohol thermometers can measure lower than mercury thermometers. They can measure temperatures down to -115°C.
Ques: Write two characteristic features of an alcohol thermometer. (2 Marks)
Ans: The two features of an alcohol thermometer are:
- They are cheaper and less harmful.
- Alcohol thermometers can measure temperatures down to -115°C.
Ques: What are the precautions that one must follow while handling thermometers? (3 Marks)
Ans: Following are the precautions that must be followed while handling the thermometers:
- Cleanse the thermometer properly before use.
- Dip it into an antiseptic liquid before and after use.
- It should be handled with care as the thermometer can easily break and the mercury inside is a toxic substance.
- Avoid touching the bulb of the thermometer either before measuring the temperature or during measurement.
Ques: Which Kind of Substance should Be Used in Glass Thermometers? (3 Marks)
Ans: Some substances have the ability to modify their properties as a function of temperature. Thermometric materials are substances that show a change in temperature. Some compounds, for example, expand when heated, while others alter colour, electric resistance, and so on. Almost all substances expand when heated. Liquids expand when heated, making them ideal thermometric materials. The thermometric substance used in most common thermometers is a suitable liquid.
Ques: Which properties should be present in thermometric liquid? (3 Marks)
Ans: The qualities of a thermometric liquid should be as follows:
- It must be clearly visible.
- It should have a consistent rate of thermal expansion.
- Its freezing point should be low.
- Its boiling point should be high.
- It must not moisten the glass.
- It should be a good heat conductor.
- Its specific heat capacity should be low.
Ques: Why is mercury used in thermometers instead of water? (3 Marks)
Ans: Mercury is used in Thermometer because:
- It has a low freezing point of -39 degrees Celsius.
- It has a very high boiling point of 357 degrees Celsius.
- It expands linearly.
- It provides precise measurements.
- It is a good conductor of heat.
- Quick response time
- It has a wide temperature range.
For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates
Also Read:
Comments