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Question
Why cannot a clinical thermometer be used to measure high temperature?
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Solution
Clinical Thermometer (or doctor's thermometer) is used for measuring a person's temperature.
The temperature range that is marked on a clinical thermometer is about 35∘ C to 43∘ C (or 95∘ F to 109∘ F).
After a clinical thermometer has been used to record a patient's temperature, the mercury is prevented from contracting into the glass bulb by the constriction (kink) unless the thermometer is jerked.
The thermometer is the device used to measure temperature.
The extremely fine tube (narrow bore) of a thermometer is called a capillary.
The boiling point of water (or condensing point of steam) is 100∘ C or 212∘ F or 373 K.
The freezing point of water (or melting point of ice) is 0∘ C or 32∘ F or 273 K.
These temperatures are typically used in the calibration of thermometers and are known as the fixed points.
The temperature range that is typically marked on a laboratory thermometer is −10∘ C to 110∘ C.
Alcohol, which is used as a thermometric liquid, has the following characteristic properties :
1. Alcohol has a very low freezing point of about −112∘ C and hence is suitable in thermometers to record very low temperatures.
2. Alcohol has a low boiling point of about 78∘ C and therefore cannot be used to measure high temperatures.
3. Alcohol can be colored brightly (by adding a dye, generally red) and then it is clearly visible through the glass.
4. Alcohol expands more than mercury.
5. Alcohol is fairly inexpensive.
6. Alcohol wets glass.
7. Alcohol is not a good conductor of heat.
Mercury, which is used as a thermometric liquid, has the following characteristic properties :
1. Mercury has a high boiling point of about 357∘ C and therefore can be used to measure temperatures as high as 357∘ C.
2. Mercury has a freezing point of about −39∘ C and hence is suitable in thermometers to record low temperatures (although not very low temperatures).
3. Mercury is opaque and has a shining silvery color of its own, making it clearly visible in the capillary tube of a thermometer.
4. Mercury needs very little heat to expand and so it can easily measure the temperature of a body without causing a decrease in the body's temperature.
5. Mercury does not stick to the side of the glass capillary tube of a thermometer. Therefore, it allows accurate temperature measurement.
6. Mercury is a good conductor of heat.
7. Mercury is relatively expensive.
The temperature range that is marked on a clinical thermometer is about 35∘ C to 43∘ C (or 95∘ F to 109∘ F).
After a clinical thermometer has been used to record a patient's temperature, the mercury is prevented from contracting into the glass bulb by the constriction (kink) unless the thermometer is jerked.
The thermometer is the device used to measure temperature.
The extremely fine tube (narrow bore) of a thermometer is called a capillary.
The boiling point of water (or condensing point of steam) is 100∘ C or 212∘ F or 373 K.
The freezing point of water (or melting point of ice) is 0∘ C or 32∘ F or 273 K.
These temperatures are typically used in the calibration of thermometers and are known as the fixed points.
The temperature range that is typically marked on a laboratory thermometer is −10∘ C to 110∘ C.
Alcohol, which is used as a thermometric liquid, has the following characteristic properties :
1. Alcohol has a very low freezing point of about −112∘ C and hence is suitable in thermometers to record very low temperatures.
2. Alcohol has a low boiling point of about 78∘ C and therefore cannot be used to measure high temperatures.
3. Alcohol can be colored brightly (by adding a dye, generally red) and then it is clearly visible through the glass.
4. Alcohol expands more than mercury.
5. Alcohol is fairly inexpensive.
6. Alcohol wets glass.
7. Alcohol is not a good conductor of heat.
Mercury, which is used as a thermometric liquid, has the following characteristic properties :
1. Mercury has a high boiling point of about 357∘ C and therefore can be used to measure temperatures as high as 357∘ C.
2. Mercury has a freezing point of about −39∘ C and hence is suitable in thermometers to record low temperatures (although not very low temperatures).
3. Mercury is opaque and has a shining silvery color of its own, making it clearly visible in the capillary tube of a thermometer.
4. Mercury needs very little heat to expand and so it can easily measure the temperature of a body without causing a decrease in the body's temperature.
5. Mercury does not stick to the side of the glass capillary tube of a thermometer. Therefore, it allows accurate temperature measurement.
6. Mercury is a good conductor of heat.
7. Mercury is relatively expensive.
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