Thermometers - class-VII

The above statement is true.

(A) The mercury level should be below $35^{o}C$ or $94^{o}F$ , because minimum reading of a clinical thermometer is $35^{o}C$ hence it must be at lowest level to measure the right temperature .

The range of clinical thermometer is from $35^{o}C$ or $94^{o}F$  to $42^{o}C$ or$108^{o}F$.

The mercury level should be below $35^{o}C$ or $94^{o}F$, because minimum temperature of human body can not be below $35^{o}C$. Hence, it must be at lowest level to measure the temperature of human body correctly.

Bimetallic thermometer include two different metals , bonded together . These two metals have different coefficients of thermal expansion , due to this they expand or contract at different rates , when put into a temperature change together .This is the principle of a bimetallic thermometer .

Water cannot be used in thermometer because of its higher freezing point and lower boiling point than other liquids .  If water is used in a thermometer , it will start phase change at $0^{o}C$ and $100^{o}C$ and will not measure temperature , out of this range . This range is very small as compared  to other liquids as mercury , having freezing point about $-39^{o}C$ and boiling point $356^{o}C$ .

Our body temperature cannot fall below $35^{o}C$ or $95^{o}F$ , because below this temperature body will suffer hypothermia .

Normal body temperature varies by person, age, activity, and time of day. The average normal body temperature is generally accepted as $98.6°F (37°C)$.

A laboratory thermometer is dipped in a beaker containing hot water. As the thermometer is removed the mercury level will fall.

A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the digital sensor in an infrared thermometer) in which some change occurs with a change in temperature, and  2.some means of converting this change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer or the digital readout on an infrared model). Thermometers are widely used in industry to monitor processes, in meteorology, in medicine, and in scientific research.thermometer be dipped inside beaker containing water vertically

A pot of boiling water is actually slightly higher than the boiling point. The boiling point is defined as the temperature at which the vapour pressure is exactly equal to the external pressure. The “Normal Boiling Point” is the boiling point at exactly 1 atm of pressure. If you look closely at a pot of. Piling water you'll notice bubbles rising from the bottom of the pot. Those bubbles are pure water vapour and since they have pushed back the water that is on top of themselves and the air over the water, they must have had a pressure greater than the external pressure to do that. Those bubbles will stop expanding when the pressure just exactly equals the boiling point and will stay there as they finish rising in the pot. This, the steam just above the water will be a better measure of the boiling point because it will not yet have had a chance to cool down.

A laboratory thermometer is dipped in a beaker containing ice. As the thermometer is removed the mercury level will rise.

A laboratory thermometer is a tool used in laboratories to measure temperature with high accuracy. It can be partially or fully immersed in the substance being measured. A laboratory thermometer is recognizable by its long stem with a silver bulb at the end. The silver color in the bulb normally indicates the presence of mercury. Mercury expands as the temperature increases, thus raising the reading, while decreasing temperatures contract the mercury, lowering the reading. Mercury-in-glass thermometers are less used in the 21st century as preference is shifted to other types of thermometers, such as digital, alcohol-filled and organic-based thermometers.

A laboratory thermometer is used for measuring temperatures other than the human body temperature. It ranges from -10˚C to 110˚C. Laboratory thermometers are designed for lab purposes such as checking boiling point, freezing point, or temperature of other substances

Thermoelectric pyrometer is an instrument which uses one or more thermocouples to measure high temperature . 

$\begin{array}{l} By, , u\sin  g, the, , formula \ \dfrac { { { T _{ t } }-{ T _{ fP } } } }{ { { T _{ BP } }-{ T _{ fp } } } } =\dfrac { { T-0 } }{ { 100-0 } }  \ \dfrac { { { T _{ t } }-20 } }{ { 150-20 } } =\dfrac { { 60 } }{ { 100 } }  \ { T _{ t } }-20=\dfrac { { 60\times 130 } }{ { 100 } }  \ { T _{ t } }=78+20 \ ={ 98^{ \circ  } } \ Hence,, the, option, C, , is, the, correct, answer. \end{array}\ $

Alcohol thermometer.
Alcohol expands uniformly.

The mercury thermometer can be used above its boiling point by filling up the space above mercury with nitrogen at high pressure because as pressure increases, boiling point also increases.

In this process, thermal equilibrium will eventually be reached after inserting the thermometer in hot pot. Hence heat is transferred from the water to the thermometer. 

$(x-20)/(80-20) =(C-0)/(100-0)$
$(x-20)/60=(C-0)/100$