Question

Name three kinds of temperature-measuring devices that work on the principle of thermal expansion. Explain how each works and what their typical characteristics are.

Answer 1

Thermal expansion is the process, which is responsible for changes in shape, size for volume of matter as a response to the variation in temperature. When temperature increases, particles get more kinetic energy.. thereby needs more space.. and resulting in the consumption of more space. Therefore due to thermal expansion, an object is expanded or gets larger in size.

This phenomenon of thermal expansion,is deployed in several devices for measuring the temperature. Mainly thermometer is used for measuring body temperature. Several kinds of thermometers are,medical thermometers, infrared thermometers, Mercury thermometers, pyrometers..etc.

MEDICAL THERMOMETERS

Used for body temperature measuring. Thermometers, which are manufactured in the 20th century are, Mercury thermometers. These are having higher sensitivity and accuracy.. a narrow place is provided for the faster rising movement of Mercury inside it. For preventing falling on its own, a kink is provided on the tube. Usually doctors are using this kind of thermometer, hence it is called doctors thermometers.it measures the body temperature at a range of 35 to 45 degree Celsius. Before and after usage,medical thermometer Rs are cleaned using alcohol.

DIGITAL THERMOMETERS.

Temperature measurement using electronic circuits is used here. The captured information is fed into the microchip, and after going to various processes, numerical values are displayed on the screen. These are more advanced, inexpensive, fast and accurate thermometers. Tip of the thermometer is placed on specific product places, and wait until an alarm beeps. After that temperature value is displayed on the screen. Metallic tip is cleaned using alcohol or cotton.

INFRARED EAR THERMOMETERS.

This type of thermometers are used to detect the temperature of eardrum. With the help of a heat source,body heat is captured in the form of infrared energy. This is according to the laws saying that, precise temperature calculation can be done, by using the radioactive emission of a object, using its emission spectrum... Without any direct contact. Tip of the thermometer is placed inside ear and pointed towards nose, displays temperature value on screen. These are fast, accurate but a bit expensive.

THERMOSTATS

Switching function of an electrical circuit, whether it is open or closed depending upon, the temperature is processed in a simple control system called thermostats. It works under the principle of thermal expansion. Matter gets bigger in size when heated up and shrinks, when freezed. These are very efficient and ease devices.

THERMISTORS

These are resistors used in electrical circuits, whose resistance is temperature dependent. Widely used in temperature sensors.. with NTC thermistors, resistance is inversely proportional to temperature. With PTC thermistors.. resistance is directly proportional to temperature. These resistors are connected in series with a circuit. It protects the circuit from over current issues, resettable fuses. With limited temperature range, thermistors are having greater precision.

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