Heat Test

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Heat Test - 29

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Weekly Quiz Competition

Question 1
1 / -0

$$500 g$$ of hot water at $${ 60 }^{ \circ }C$$ is kept in the open till its temperature falls to $${ 40 }^{ \circ }C$$. Calculate the heat energy lost to the surroundings by the water. ( specific heat of water = 4200 J $${ { kg }^{ -1 } }^{ \circ }{ C }^{ -1 }$$)

A
$$2400 J$$

B
$$5000 J$$

C
$$40000 J$$

D
$$42000 J$$

Solution

Given , $$m=500g=0.5kg , \theta_{1}=60^{0}C , \theta_{2}=40^{0}C$$
We have , specific heat of water $$c=4200J/kg-^{o}C$$
Now , heat lost to the surroundings by the water is given by the definition of specific heat c ,
$$Q=mc\Delta \theta=mc(\theta_{1}-\theta_{2})$$
or $$Q=0.5\times4200\times(60-40)=42000J$$
Question 2
1 / -0

Before using the clinical thermometer mercury level should be below:

A
$$ 45 ^\circ C$$

B
$$ 35 ^\circ C$$

C
$$ 95 ^\circ C$$

D
$$ 55 ^\circ C$$

Solution

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.
Question 3
1 / -0

On a cold day when a room temperature is $$15^oC$$, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of $$15^oC$$, because

A
metals have higher thermal capacity than plastics

B
plastics have a lower density than metals

C
metals are good conductor of heat

D
plastics have a higher thermal conductivity than metals

Solution

On a cold day when a room temperature is $$15^oC$$, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of $$15^oC$$ because metals are good conductor of heat, so they could absorb and release heat in a better way than insulators.
Question 4
1 / -0

The degree of hotness or coldness of a body is ......... .

A
Temprature

B
Coldness

C
Thermometer

D
Heat

Solution

The degree of hotness or coldness of a body is Temperature.
Example
Boiling water seems much hotter than ice because boiling water temperature is at $$100^{\circ}C$$ and ice temperature is at $$0^{\circ}C$$.
Question 5
1 / -0

Lake water never completely freezes because

A
Principle of conduction prevents it

B
Principle of convection prevents it

C
both of the above

D
none of the above

Solution

Lake water never completely freezes because principle of convection prevents it.
Warm water gets more dense when it gets colder and therefore sinks. This fact may lead to fact that ice should form on bottom of lake first. But water colder than $$4^oC$$ begins expanding and become less dense as it gets closer. As a result, close to freezing, colder water floats on top and warmer water sinks to bottom. Eventually, the coldest water, which has floated to top of lake in wintery condition freezes to form ice layer. When the water freezes to ice, the ice becomes significantly less dense than water can continues to float on lake's surface. And then lake never completely freezes. So, in this manner; principle of convection prevents it.
Question 6
1 / -0

Among the following what should not be done while or before using a clinical thermometer?

A
Ensure that before use the mercury level is below $$35\ ^0C$$.

B
Wash the thermometer with hot water.

C
Handle the thermometer with care, as you handle any glass articles.

D
Don't hold the thermometer by the bulb while reading it.

Solution

(A) The mercury level should be below $$35^{o}C$$ or $$94^{o}F$$ because the minimum reading of a clinical thermometer is $$35^{o}C$$ hence it must be at the lowest level to measure the right temperature.
(B) If we wash the thermometer with hot water, the mercury will expand due to heat given by hot water and will rise to a higher temperature. If the water is very hot, it may result in damage to the thermometer. Hence it must not be done.
(C) It must be handled with care as being made of glass and mercury inside it is poisonous.
(D) If we hold the bulb by our hand, the thermometer will take the heat from the hand and will show a wrong reading hence we should not hold it by the bulb
,
Question 7
1 / -0

In experiment of heat transfer by convection, water inside the pipe completely gets heated (with the application of heat source). This can be explained best by which of the following statements,

A
Differences in densities produced between the bottom and the top of water , in turn produce the driving force which continuously circulates the water.

B
A continuous conductive channel is produced between the different layers of water in the pipe which circulates the heat.

C
both the above explains correctly

D
all of the above

Solution

When the water in below part of pipe is heated, its density decreases. Hence less density water moves up (shown in red) and cooler water with more density comes down (shown in blue). It is nothing but convection as convection is mode of heat transfer in which heat is transferred in fluid (liquid or gas) by molecular motion.
Question 8
1 / -0

Boiling water can be measured by

A
Clinical thermometer

B
Laboratory thermometer

C
Both may be used conveniently

D
Both of them can not be used

Solution

Laboratory thermometers are used to measure temperatures or temperature changes with a high degree of precision. That's why these are mainly used in laboratories. For exp : To measure boiling points of solutions, water etc. They are made up of glass , the strength of which, is increased through thermal tempering or annealing. Types : liquid-in-glass, bimetallic strip, infrared based thermometer.
Hence, the answer is Laboratory thermometer.
Question 9
1 / -0

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

A
rise

B
fall

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

D
neither rise nor fall

Solution

As the temperature of hot water is much higher than the room temperature the level of mercury rises but when it is removed from the beaker, the mercury level starts descending as the temperature of the room is less than the temperature of hot water.
Question 10
1 / -0

What is the measurement of temperature in Celsius scale in the above figure?

A
$$25^oC$$

B
$$30^oC$$

C
$$26^oC$$

D
$$29^oC$$

Solution

The main scale reading of thermometer reads $$30^oC$$ and sub scale reading is zero.
the sub scale reading has 5 division on it and between them it has $$10^o$$
Hence each division measures about $$\dfrac{10^o}{5}=2^o$$
Therefore reading of thermometer is $$30^oC+0\times2^o=30^oC$$

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Heat Test - 29

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Heat Test - 29

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Question 1

$$2400 J$$

$$5000 J$$

$$40000 J$$

$$42000 J$$

Solution

Question 2

$$ 45 ^\circ C$$

$$ 35 ^\circ C$$

$$ 95 ^\circ C$$

$$ 55 ^\circ C$$

Solution

Question 3

metals have higher thermal capacity than plastics

plastics have a lower density than metals

metals are good conductor of heat

plastics have a higher thermal conductivity than metals

Solution

Question 4

Temprature

Coldness

Thermometer

Heat

Solution

Question 5

Principle of conduction prevents it

Principle of convection prevents it

both of the above

none of the above

Solution

Question 6

Ensure that before use the mercury level is below $$35\ ^0C$$.

Wash the thermometer with hot water.

Handle the thermometer with care, as you handle any glass articles.

Don't hold the thermometer by the bulb while reading it.

Solution

Question 7

Differences in densities produced between the bottom and the top of water , in turn produce the driving force which continuously circulates the water.

A continuous conductive channel is produced between the different layers of water in the pipe which circulates the heat.

both the above explains correctly

all of the above

Solution

Question 8

Clinical thermometer

Laboratory thermometer

Both may be used conveniently

Both of them can not be used

Solution

Question 9

rise

fall

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

neither rise nor fall

Solution

Question 10

$$25^oC$$

$$30^oC$$

$$26^oC$$

$$29^oC$$

Solution

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