Tag: heat - measurement

Questions Related to heat - measurement

One litre of water at $30^{o}C$ is mixed with one litre of water at $50^{o}C$. The temperature of the mixture will be

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. 80C

  2. more than 50C but less than 80C

  3. 20C

  4. between 30C and 50C

Show answer
Correct Option: D
Explanation:
Let the first volume of water be V1. Let the second volume of water be V2. Let the initial temperature of the first volume of water be θ1. Let the initial temperature of the second volume of water be θ2.

Let the energy required to heat a unit volume of water by unit temperature by C.

So, if the final temperature is θfinal, we have

heat gained by the first volume of water

$=V _1×C×(θ _{final}−θ _1)$

and

heat lost by the second volume of water

$=V _2×C×(θ _2−θ _{final}).$

By the law of conservation of energy,

heat lost = heat gained

∴$V _1×C×(θ _{final}−θ _1)=V _2×C×(θ _2−θ _{final})$

∴$V _1θ _{final}−V _1θ _1=V _2θ _2−V _2θ _{final}$

∴$θ _{final}=V _1θ _1+V _2θ _2V _1+V _2$

Substituting the given values,

$θ _{final}=\dfrac{30+50}{2}=40^∘C$.

The answer is option D

Human body temperature is well measured by 

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. A clinical thermometer

  2. A laboratory thermometer

  3. Thermostat

  4. Both A & B can be used

Show answer
Correct Option: A
Explanation:
A clinical thermometer is a thermometer used to measure human body temperature. Most old ones use mercury thermometer. It is accurate and sensitive, because it has a narrow place where the mercury level rises very fast.

These thermometers are used in clinics by doctors, so they are also called a doctor's thermometers or medical thermometers. Most of them show both Celsius scale and Fahrenheit temperature scales. The scale runs from 35 degree Celsius to 42 degree Celsius.

Medical thermometers are cleaned before and after each use, with alcohol.

It has a kink which does not allow the mercury level to fall on its own.

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

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. rise

  2. fall

  3. it may rise or fall depending upon how much water is kept inside the beaker

  4. neither rise nor fall

Show answer
Correct Option: B
Explanation:

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

As the temperature of hot water is much higher than the room temperature th level of mercury rises but when it is removed then the thermometer comes down as the temperature of room is less than the temperature of hot water hence level will fall

Choose the correct option

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Temperature of a water kept inside a beaker is measured when the laboratory thermometer is held inside the water

  2. Temperature of a water kept inside a beaker is measured when the laboratory thermometer is removed from the water

  3. Temperature of our body is measured when the clinical thermometer is kept inside the mouth

  4. Temperature of our body is measured when the clinical thermometer is removed from the mouth

Show answer
Correct Option: A,D
Explanation:
A.Temperature of a water kept inside a beaker is measured when the laboratory thermometer is held inside the water.This gives accurately the temperature of water in beaker.
B
Temperature of a water kept inside a beaker is measured when the laboratory thermometer is removed from the water.This method is wrong as thermometer reading will be drop as it removed from the beaker.Hence this will give error in reading.
C
Temperature of our body is measured when the clinical thermometer is kept inside the mouth.In the clinical thermometers the maximum temperature is first allowed to reach then we remove the thermometer and  take the reading.Hence temperature inside mouth gives error in reading 
D
Temperature of our body is measured when the clinical thermometer is removed from the mouth.In the clinical thermometers the maximum temperature is first allowed to reach then we remove the thermometer and  take the reading.Hence this method is correct.

A clinical thermometer can not be used to measure

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Room temperature

  2. Human body temperature

  3. Temperature of a boiling water

  4. Temperature of a lake water

Show answer
Correct Option: C
Explanation:
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 $35^oC$ to $43^oC$ (or $ 95^oF$ to $109^oF). $
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.
Hence cannot be used to measure temperature of boiling water which is about $100^oC$

How should a thermometer be dipped inside beaker containing water

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Vertically

  2. Tilted

  3. Any of the above way

  4. None of the above way

Show answer
Correct Option: A
Explanation:

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

Choose the correct option 

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. A clinical thermometer should be washed using water before and after use

  2. A clinical thermometer should be washed using antiseptic solution before and after use

  3. A clinical thermometer can be used after it is heated by fire

  4. None of the above

Show answer
Correct Option: B
Explanation:
A clinical thermometer is a thermometer used to measure human body temperature. Most old ones use mercury thermometer. It is accurate and sensitive, because it has a narrow place where the mercury level rises very fast.

These thermometers are used in clinics by doctors, so they are also called a doctor's thermometers or medical thermometers. Most of them show both Celsius scale and Fahrenheit temperature scales. The scale runs from 35 degree Celsius to 42 degree Celsius.

Medical thermometers are cleaned before and after each use, with alcohol.

It has a kink which does not allow the mercury level to fall on its own.

Choose the wrong statement when we measure the temperature of a water kept in a beaker: 

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Thermometer should be kept vertical so that the bulb does not touch sides or bottom of the beaker

  2. Thermometer should be kept vertical so that the bulb touches the bottom of the beaker

  3. Thermometer should not be kept tilted so that the bulb touches sides or bottom of the beaker

  4. Thermometer should be kept tilted without touching bottom or sides of the beaker

Show answer
Correct Option: A
Explanation:

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.


Hence Option A is correct

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

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. rise

  2. fall

  3. either rise or fall depending upon how much ice is kept inside the beaker

  4. neither rise nor fall

Show answer
Correct Option: A
Explanation:

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

The temperature of ice is about 0 degree celsius and temperature of  room is abut 34 degree when thermometer is removed mercury will expand and level will rise.

A laboratory thermometer can not be used to measure

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Temperature of ice

  2. Temperature of pond water

  3. Temperature of human body

  4. Temperature of boiling water

Show answer
Correct Option: C
Explanation:
Laboratory thermometer are used to take measurements in laboratories mainly. They can't be used to measure body temperature of a human. It is because of two reasons.  :
$(1)$ Due to vast difference in the range of operating temperature.
$(2)$ Due to difference in time for which the indicated temperature is held at that level.
Hence, the answer is Temperature of human body.