Heat - Class 7 Physics - Extra Questions

At what temperature does water begin to expand when cooled ?

When liquid water is cooled, it contracts like one would expect until a temperature of approximately $$4^{\circ}C$$ is reached. After that, it expands slightly until it reaches the freezing point, and then when it freezes it expands by approximately $$9%$$.


Name three bad conductors of heat.

Conductors - transfer of heat takes place; allow heat to pass through them
Bad conductors of heat i.e. insulators:
  1. Glass
  2. Plastic
  3. Rubber
  4. Wood 


Give reason : we wear a number of garments in winter rather than one thick garment 

When we wear a number of garments, there are extra layers of air trapped between each garment which act as an insulator and do not allow the heat from the body to flow out. Thus we feel more warm and comfortable by wearing a number of garments than wearing a thick single garment.


Give reason : An iron chair feels colder than a wooden chair in winter 

A chair made of iron appears colder because iron being a good conductor of heat, it looses its heat to the surrounding at night. But the wooden chair remains the same because wood is a bad conductor of heat and so no heat is lost from it.


Give reason as to why woolen clothes are more preferable in winter.

Woolen clothes contains a large amount of trapped air. Since air is a bad conductor of heat it does not allow the body heat to flow out, as a result of which, we feel warm and comfortable. 


A cold steel spoon is dipped in a cup of hot milk. It transfer heat to its other end by the process of ___________.

Conduction.

Conduction is the movement of heat through a substance by the collision of molecules. This process continues until heat energy from the warmer object spreads throughout the cooler object, like the heat from the milk spreading throughout the metal spoon dipped in it.



Which of the following is the worst conductor of heat
(A) Asbestos         (B) Rubber
(B) Plastic             (C) Graphite

 Plastic, Rubber and Asbestos are worst conductors of heat. because they don't have a proper structure in place. All these materials don't have a proper lattice structure.


Fill in the blanks:                    
We use a _____________ for measuring the temperature of a body.

We use a thermometer for measuring the temperature of a body.

Explanation:

  • Thermometer is used to measure the temperature of a body.

  • It shows the temperature in degrees Fahrenheit (°F) or degrees Celsius (°C).



Name a liquid which is a good conductor of heat.

Mercury is a good conductor of heat.


Poor conductors are known as ____. 

$$\textbf{Insulators}$$
An electrical insulator is a material in which the electron does not flow freely or the atom of the insulator have tightly bound electrons whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. 


Name the instrument used to measure the temperature of a body.

To measure the temperature of a body with the help of a thermometer.


A temperature is an objective comparative measure of how hot or cold a body is. Its S.I. unit is kelvin $$(K).$$ Type 1 for true and 0 for false.

A temperature is an objective comparative measure of how hot or cold a body is.  Its S.I. unit is kelvin $$(K).$$ So the given statement is true.


Why are the mud houses provided with thatched roofs?

Mud is a bad conductor of heat and so is the air trapped in the thatched roof. In summer the heat from outside is not allowed to flow in and hence it keeps cool. Similarly in winter, the heat from inside does not flow out and it keeps the house warm.


What is a Thermostat?

The thermostat is the device to detect the variation of temperature in a system. Which wants to maintain the constant temperature. For example, it is used to control the flow of electric current to a heating or cooling unit or of a heated or coaled gas. The thermostat generates signals usually electrical when the temperature varies from the desired value. It is also used in some type of fire detection warning system.


Name three good conductors of heat

Most metals are the good conductors of heat,
Gold, Silver, Copper, Aluminium, Iron etc are good heat conductors as well as electrical conductors.


Describe a Pyrometer.

Pyrometer is a instrument for measurement of temperature. Most of pyrometer measured relatively high temperature such as encountered in furnaces. Pyrometers are closely related to bolometer and thermistor and are used in thermometry. On the basis of how it works, it has mainly four types :
$$1.$$ Radiation pyrometer.
$$2.$$ Optical pyrometer.
$$3.$$ Resistance pyrometer
$$4.$$ Thermocouple pyrometer.



Define Temperature of a body.

Temperature is the measure of degree of its hotness or coldness of a body.


Describe the construction of a laboratory thermometer.

Laboratory thermometer consists of a bulb with a long capillary tube.The wall of the bulb is made thinner and the capillary tube is made narrower in order to make the thermometer more sensitive.
Mercury thermometer can be used to measure both hot and cold substances.Usually,laboratory thermometer is made in Celsius scale ranging from $$-10°C\quad to\quad 110°C$$.It is used to measure temperature with high accuracy.It is constructed on the basis of mercury based thermometers.


Why does a clinical thermometer have a kink?

The kink is there to prevent the mercury to fall back. When we hold the thermometer to measure the graduation, if the kink is not there, we will be unable to read the graduation as the mercury level will fall.
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Give reason as to why a newly made quilt is warmer than an old one.

A new quilt is warmer because the air which is trapped inside the cotton or woollen clothing acts as an insulator and does not allow the transfer of heat. However, when the quilt gets older, the air spacing of the cotton or wool gets compressed it no longer remains a good insulator. Hence, the person does not feel warm.


Laboratory thermometers have a range of  $$-10^oC$$ to $$_______$$$$^\circ$$C 

Laboratory thermometers have a range of $$-10^oC$$ to $$110^oC$$.
These types of thermometers are used in the lab to measure the freezing point, the boiling point of water, and other laboratory purposes. 


State four reasons for using mercury as a thermometric liquid.

Reasons for using mercury as a thermometric liquid are :
(a)  Mercury has uniform contraction and expansion 
(b) Mercury does not stick to the sides of the capillary tube 
Thus it helps in recording accurate temperature 
(c) Mercury is opaque and shining Thus it can be easily seen as a fine thread in the capillary tube
(d) It has high boiling point $$ \displaystyle 257^{\circ}C $$ and low freezing point ($$ \displaystyle -39^{\circ}C $$) so it can be used to measured and only wide range of temperatures 


The degree of hotness and coldness of the body is called ____________.

The degree of hotness and coldness of the body is called temperature. The temperature decides the flow of heat. The heat is always flows from higher temperature to lower temperature. 


The degree of hotness or coldness of a body is called __________ (heat/temperature).

Temperature is known as the degree of hotness or coldness of a body.


Temperature is expressed in __________(degree centrigrade $$OR$$  joule).

The most commonly used scales are the Celsius scale, denoted in °C (informally, degrees centigrade), the Fahrenheit scale (°F), and the Kelvin scale. The kelvin (K) is the unit of temperature in the International System of Units (SI), in which temperature is one of the seven fundamental base quantities.


State similarities and differences between the laboratory thermometer and the clinical thermometer.

Similarities:
  1. Bulbs contain mercury.
  2. Glass tubes are long, narrow and uniform.

Differences:
  1. The clinical thermometer is used to measure body temperature, however, laboratory thermometer is not used for the purpose of measuring body temperature.
  2. The temperature range of clinical thermometers is 35°C to 42°C and that of laboratory thermometers is -10°C to 110°C.
  3. The least count of both the thermometers is different.
  4. The clinical thermometer is can be tilted while reading the temperature values whereas laboratory thermometer need to be kept upright.


Is ebonite handles would not permit heat to be conducted from hot utensil to hand?

Yes, Ebonite is bad conductor of heat and thus it will not conduct the heat from utensils to hand. 


The ............... of the body rises, when it is heated.

The temperature of body rises, when it is heated


What is the use of kink in clinical thermometer?

Kink  in  the Mercury thermometer helps to prevents the falling of mercury present in capillary  tube into bulb. It ensures that the user takes the correct reading of temperature.

That's  the reason a person before taking  a new reading must give a sudden shake to the clinical thermometer so that the mercury level comes to normal .

Hence Kink in mercury thermometer plays a important  role without which appropriate reading of temperature is not possible.


Clothes of ________ (dark, white) colors absorb heat better than clothes of light colors.

A black object absorbs all wavelengths of light and reflects none and that's why it appears black. Consequently, black absorbs the most heat. Objects that are white, on the other hand, reflect all wavelengths of light and that's why they appear white to us, therefore absorb the least heat.


Temperature of boiling water cannot be measured by a ________ (clinical, laboratory) thermometer.

Clinical.


Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing?

Explanation: One thick piece of clothing do not have a layer of air inside it. When there is more than one layers of cloth there will be a layer of air be present between layers. Air acts as insulator of heat. This layer prevents our body heat to escape in the surroundings. More layers of thin clothes will allow more air to get trapped and as a result, we will not feel cold. So wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.


A laboratory thermometer A is kept $$7\,cm$$ away,an the side of the flame while a similar thermometer.B is kept $$7\,cm$$ above the flame as shown in figure,which of the thermometer $$A$$ and $$B$$ , will show a greater rise in temperature.Give reason for your answer.

Air near candle gets heated up and after this it rises by convection so the thermometer $$B$$ will receive more heat than the thermometer $$A$$ So, according to the given condition thermometer $$B$$ will show a greater rise in temperature.


What is the difference in the temperatures and thermometers?

Solution:-

Temperature is a measure of the degree of hotness and coldness of an object while thermometer is a device used for measuring temperatures.


What is temperature?

Temperature is a physical property of matter that quantitatively expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder. Temperature is measured with a thermometer.


To keep her soup warm Paheli wrapped the container in which it was kept with a woollen cloth Can she apply the same method to keep a glass of cold drink cool? Give reason for your answer.

Woollen is a bad conductor of heat, that is it is an insulator. So, when Paheli uses a woollen cloth to wrap the cold drink bottle, it will work and keep the cold drink cool as there will be no transfer of heat from the outer atmosphere.


At a camp site there are tents of two shades - one made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give reason for your choice. Would you like to prefer the same tent during winter?

On a hot summer afternoon, a tent made up from white fabric will be better option as compared to the tent made up from black fabric.
Black colour is a good absorber and bad reflector of heat (sun light). On the other hand, white colour is bad absorber and an excellent reflector of heat (sun light).
So, on a hot summer afternoon a tent made up of white fabric will be preferred and on a cold winter afternoon a tent made up of black fabric will be preferred.


Fill in the blanks:
The thermometer used to measure the human body temperature is called the .............. thermometer.

The thermometer used to measure the human body temperature is called the clinical thermometer.


Is the bulb of a thermometer made of diathermic walls or adiabatic walls?

Adiabatic walls does not allow to pass heat into mercury of bulb and diathermic allows to conducts heat through it. So in the bulb of thermometer diathermic walls are used.


Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.

The jute is an insulating material and it helps ice not to melt so quickly. So, shopkeepers selling ice blocks usually cover them with jute sacks. Sometimes they use other insulating material such as saw dust, sack, newspaper, to cover an ice.


Why is it advised not to hold the thermometer by its bulb while reading it?

It is advised not to hold the thermometer by its bulb while reading it because if we hold a thermometer by its bulb, the mercury in the bulb will expand due to our body temperature and effect the actual reading.


You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so?

The jerks given to the thermometer before using it in order to get an accurate reading, the jerks allow the mercury level to flow into the bulb, below from the normal temperature.


Fill in the blanks:            
A person is said to have fever if his body temperature is more than _________.

A person is said to have a fever if his body temperature is more than 98.6°F.

Explanation:

  • According to some studies, the normal body temperature can range from 97°F (36.1°C) to 98.6°F (37.2°C).

  • If your body temperature is more than 98.6°F, that means you are having a fever. 



What does the temperature measure ?

Temperature measures the degree of coldness and hotness of a body.


Fill in the blanks:                   
The temperature of a normal human body is _________.

The temperature of a normal human body is $$37^0 $$ C


Write the temperature of melting ice.

The temperature of melting ice is constant and its value is $$= 0^\circ C$$


Write down the body temperature of a healthy person.

  • A healthy person's temperature is 98.6 degrees Fahrenheit (37.0 degrees Celsius).



What is meant by the term temperature.

Temperature is a quantity which tells the thermal state of a body (i.e. the degree of hotness or coldness). It determines the direction of flow of heat when the two bodies at different temperatures are placed in contact, which is from higher temperature to lower temperature body.


The S.I. unit of temperature is ____________.

The S.I. unit of temperature is Kelvin.

Explanation:

  • The kelvin (K) is the SI unit of temperature.

  • However, the degree Celsius (°C) is another temperature unit. 

  • Subtract 273.15 from the numerical value of the temperature expressed in kelvin to get the temperature in degrees Celsius.




Name the S.I. unit and one common unit of temperature. Write their symbols also.

The S.I. unit of temperature is kelvin (symbol K).
Common unit of temperature is degree centigrade (symbol $$^\circ C$$)


Select a good and bad conductor of heat from the following:
copper, mercury, wood, iron, air, saw-dust, cardboard, silver, plastic, wool.

Part-1: Good conductors  

  • The  substances which allow the heat to pass through them easily are good conductors  of  heat.

  • Mercury, copper, silver, iron. 

  • The  above mentioned substances allow the heat to pass through them easily.


Part-2: Bad conductors 

  • The  substances which  do not allow the heat to pass through them easily are bad conductors  of  heat

  • Wood, air, saw dust, plastic, wool, cardboard. 

  • The  above mentioned substances do not allow the heat to pass through them easily.



Name a liquid which is a good conductor of heat.

Mercury is the only liquid which is good conductor of heat. That is why it is also used in a mercury thermometer.
We know that most metals are good conductors of heat as solid at room temperature. But mercury is the only good conductor of heat in a liquid state.


Why is an oven made of double walls with the space in between filled with cork?

  • As cork is a good insulator of heat.

  • The space between double walls of an oven is filled with cork.

  • This prevents the heat of the oven from escaping.




Explain why we wear woolen clothes in winter.

  • Woolen clothing contains fine pores that are filled with air. 

  • Both wool and air are poor heat conductors. 

  • As a result, we wear woollen clothes in the winter because they prevent heat transfer from the body to the environment, keeping the body warm.




What are the good and bad conductors of heat? Give two examples of each.

Part-1: Good  conductors

  • The  substances which allow the heat to pass through them easily are good conductors  of  heat.

  • Examples: Copper and iron are the best examples of good conductors. 


Part-2: Bad  conductors

  • The  substances which  do not allow the heat to pass through them easily are bad conductors  of  heat

  • Examples: Wood and cloth are the best example of bad conductors. 




Name a solid which is a good conductor of heat.

Aluminium is a good conductor of heat.


In summer, ice is kept wrapped in a gunny bag. Explain the reason.

  • The ice is kept wrapped in a gunny bag or covered with sawdust during the summer. 

  • The heat is insulated by the air that fills the fine pores of the gunny bag or saw dust. 

  • The air prevents heat from the outside from reaching the ice. 

  • As a result, the ice does not melt as quickly.




Explain why the water pipes are covered with cotton during very cold weather.

  • The water pipes are covered with cotton during extremely cold weather because air is trapped in the fine pores of the cotton. 

  • The heat is insulated by the cotton and the air. 

  • They do not transfer heat from the inside of the pipes to the outside air. 

  • As a result, cotton keeps the water in the pipes from freezing.




Why are quilts filled with fluffy cotton?

  • Fluffy cotton is used to fill quilts because cotton fibres have fine pores that trap air. 

  • Cotton and air are insulators of heat.

  • They prevent heat from leaving our bodies and thus keep us warm. 

  • Because there is no air trapped in the cotton in old quilts, the newly made quilts are warmer than the old ones.



Why is tea kettle provided with an ebonite handle?

Tea kettles are provided with wooden or ebonite handles. The wood or the ebonite being the insulator of heat, does not pass heat from the utensils to our hand. Thus, we can hold utensils or pans comfortably by their handles. 


Write the names of two conductors and insulators.

  • Conductors - Copper, Iron,
  • Insulators - Plastic, Rubber.


Why do we prefer to wear white or light coloured clothes in summer and black or dark coloured clothes in winter?

  • The  white  clothes  reflect most  of  the  sun’s heat  and  absorb  very  little  of  the  sun’s heat,  thus they keep  our  body cool.

  • While the black  or  dark-colored  clothes  absorb  most  of  the  sun’s heat  and  keep  our  body warm.

  • That's the reason we  prefer  to  wear  white  or  light  coloured  clothes  in  summer  and  black or  dark coloured  clothes.




Explain the conduction mode of heat transfer'

In conduction, the heat transfer takes place at the molecular level without actual movement of molecules, from the hottest to the coldest surface.
In the process of heat transfer, the molecules pump into their neighbors and transfer the energy to them which continue as long as heat is still being added
The transfer between bodies continue unit the temperature different decays and a state knows as thermal equilibrium occurs.
Greater the value thermal conductivity K of body better is its heat conducting capability 
For insulator this value of K is zero.


Define temperature and name its S.I. unit.

The quantity which determines the direction of flow of heat between two bodies kept in contact is called temperature. 
S.I. unit kelvin (K).


Why does a piece of ice when touched with hand, appear cool? Explain.

Ice exist zero or below zero degrees Celcius. but our body temperature is 37$$^o$$ C. Due to temperature differences, heat started to flow from our body to ice. Hence Ice feels colder on touching. 


Temperature is measured in degree _______.

Temperature is measured in degree Celsius.
Temperature is a measure of the degree of hotness of an object.


Give scientific reasons:
Before use, the clinical thermometer is jerked

Before use, the clinical thermometer is jerked so that the mercury flows back into the bulb


Why is ice packed in sawdust? Explain.

Ice is packed in sawdust because it prevents ice from melting. Sawdust is a bad conductor of heat. The air filled in the fine pores of saw dust is an insulator of heat. This air does not allow heat from outside to pass to the ice thereby preventing its melting.


Fill in the blanks
A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of______

Conduction occurs when two object at different temperatures are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature. Conduction is the movement of heat through a substance by the collision of molecules. At the place where the two object touch, the faster-moving molecules of the warmer object collide with the slower moving molecules of the cooler object. As they collide, the faster molecules give up some of their energy to the slower molecules. The slower molecules gain more thermal energy and collide with other molecules in the cooler object. This process continues until heat energy from the warmer object spreads throughout the cooler object, like the heat from the milk spreading throughout the metal spoon dipped in it. Hence, Option A is correct.



Fill in the blanks :
Temperature of boiling water cannot be measured by a ______ thermometer.

Temperature of boiling water cannot be measured by a $$\textbf{Clinical thermometer}$$ The reason behind this is the range of clinical thermometer varies between only 35° C to 42° C.


Define Conduction.

The process by which heat flows from the hotter end to colder end in solids is known as Conduction. The heat energy is transmitted through collision between neighboring atoms or molecules. All metals are good conductors of heat. 


Draw a diagram of clinical thermometer.


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Why is a person able to remove a piece of dry aluminum foil from a hot oven with bare fingers, whereas a burn results if there is moisture on the foil?

With dry aluminum, the thermal conductivity of aluminum is much greater than that of (dry) skin. This means that the heat energy in the aluminum can more readily be transferred to the atmosphere than to your fingers. In essence, your skin acts as a thermal insulator. If the aluminum is wet, it can wet the outer layer of your skin to make it into a good thermal conductor; then more energy from the aluminum can transfer to you. 
 In practical terms, when you let go of a hot, dry piece of aluminum foil, the energy transfer by heat immediately ends. When you let go of a hot and wet piece of aluminum foil, the hot water sticks to your skin, continuing the heat transfer, and resulting in more energy transfer by heat to you! 


What are insulators ? Give example.

An electrical insulator is a material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials, semiconductors, and conductors conduct electric current more easily.
Eg: Wood, plastic, etc.,


What are Conductors ? give example. 

A conductor is any piece of material that easily allows heat or electricity to pass through it. Many different materials can be conductors but metals are the best conducting materials that are available to us. A conductor allows electrons to flow freely across its surface. For example - silver, aluminium, copper, etc.


The clinical thermometer is used to measure the temperature of _____ only.

The clinical thermometer is designed to measure the temperature of $$\textbf{human body}$$ only. The temperature of human body normally does not go below 35oC or above 42oC . That is the reason that this thermometer has the range 35oC to 42oC.


It is the morning of a day that will become hot. You just purchased drinks for a picnic and are loading them,with ice, into a chest in the back of your car. (a) You wrap a wool blanket around the chest. Does doing so help to keep the beverages cool, or should you expect the wool blanket to warm them up? Explain your answer. (b) Your younger sister suggests you wrap her up in another wool blanket to keep her cool on the hot day like the ice chest. Explain your response to her.

(a) Yes, wrap the blanket around the ice chest. The environment is warmer than the ice, so the blanket prevents energy transfer by heat from the environment to the ice. 

(b) Explain to your little sister that her body is warmer than the environment and requires energy transfer by heat into the air to remain at a fixed temperature. The blanket will prevent this conduction and cause her to feel warmer, not cool like the ice. 


Give reasons.
(a) After a hot sunny day, we sprinkle water on the roof or open ground.
(b) Perspiration keeps our body cold.
(c) Ice is rubbed on burnt part of the skin

Part (a) on hot sunny day, we sprinkle water on roof or open ground because the water can absorb the heat and get converted into vapours.

Since water absorb heat so temperature of surrounding fell down and we get cooling.

Part (b) As perspiration takes place it will gives sweat, sweat will absorb the heat from our body it makes your skin feel cooler when its wet.

Hence in evaporation of sweat will cause absorption of heat making your body cold.

Part (c) Ice has latent heat, it will absorb the heat from burnt skin. Ice get converted into liquid. So it will absorb heat and gives relaxation from burning.


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What are the precautions to be taken while using a clinical thermometer.

1. Precautions to be taken while using a clinical tehermometer
2. Thermometer should be washed before and after each use, preferably with an antiseptic solution
3. do not wash the thermometer with hot water
4. ensure that before use the mercury level is below $${35}^{o}C$$
5. Read the thermometer keeping the level of mercury along the line of sight.
6. Handle the thermometer with care, as you handle any glass articles
7. Don't hold the thermometer by the bulb while reading it.


Write the principle on which the thermometer is made.

Thermometer is based on the principle that a liquid expands on heating and contracts on cooling. These liquid thermometers are based on the principal of thermal expansion.


What do you understand by the term temperature ? Distinguish between laboratory and clinical thermometers.

Degree of hotness or coldness of an object is called its temperature.
Laboratory thermometerClinical thermometer
(i) It is used to measure temperatures for scientific purposes in a laboratory.
(ii) The kink is not present.
(iii) The lower fixed point is -$$10^\circ C$$ 
and upper fixed point is $$110^\circ C.$$		(i) It is used to measure temperature of the human body.
(ii) a slight bend or kink is present near the bulb.
(iii) The lower fixed point is $$35^\circ C$$ or $$95^\circ F$$ and the upper fixed point is $$42^\circ C$$ or $$108^\circ F.$$

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Mention the two special features of clinical thermometer.

The capillary has a narrow bend called constriction. The range of clinical thermometer is between $${35}^{o}C$$ and $${42}^{o}C$$


Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.

Explanation

As we know air is the bad conductor of heat and when we wear more layers cloths than air trapped in between and heat does not allow to escape from that trapped air layer and we feel more hotter in this.




Fill in the blanks:
The normal temperature of human body is .......$$^\circ C$$ or ......... $$^\circ F.$$

The temperature of a normal human body is 37

°C.

Explanation:

  • The average normal body temperature is 98.6 degrees Fahrenheit (37 degrees Celsius). 

  • According to some studies, the normal body temperature can range from 97°F (36.1°C) to 99°F (37.2°C).



Draw a neat labelled diagram of a laboratory thermometer.

Labeled diagram of of a laboratory thermometer is shown in the figure below:





State the three units of temperature.

  • The  S.I.  unit  of  temperature  is  kelvin  or  K.  

  • And the  other  most  common  unit  of  temperature is degree  Celsius  (°C)  and  degree  Fahrenheit  (°F). 





Write the construction of clinical thermometer.

Construction: It consists of a cylindrical bulb B which is filled with mercury. A capillary tube T of uniform and fine bore is attached to the bulb. Just above the bulb at point C the tube is made narrow and bent. Since the temperature of human body varies from 95°F to 110°F, the thermometer is calibrated in this temperature range. Each degree is divided into five small equal divisions. Besides, as the temperature of a healthy man is 98.4°F, so special bold or red mark is made on the surface of the thermometer at 98.4°F.
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What are the precautions should we take while using the clinical thermometer ?

The precautions should we take while using the clinical thermometer are:
1. Thermometer should be washed before and after use, preferably with an antiseptic solution. 
2. Ensure that before use the mercury level is below $$35^\circ C.$$ 
3. Read the thermometer keeping the level of mercury along the line of sight. 
4. Handle the thermometer with care. If it hits against some hard object, it can break.
5. Don't hold the thermometer by the bulb while reading it. 


How is the temperature read in the clinical thermometer?

The temperature of a healthy human body is approximately 37°C.
The temperature of human body is measured with the help of a clinical thermometer which can measure temperatures in range of 35°C to 42°C.
 To measure the temperature a person has to hold the tip of the thermometer either under the armpit or in the mouth under his tongue for a minute. Then we observe the number against the point at which the mercury column stop rising further. This number indicates the body temperature of the person.


Why are traditional clinical thermometers shook before checking temperature?

The thermometer are shook before checking the temperature levels, so that the mercury comes back to its initial point i.e. where it had been before the temperature was taken.


Why does the clinical thermometer has a range?

The clinical thermometer is designed
to measure the temperature of human
body only. The temperature of human
body normally does not go below 35 C
or above 42 C. That is the reason
that this thermometer has the range
35 C to 42 C.


Class 7 Physics Extra Questions