MCQ Questions for Class 7 Physics Heat Quiz 7

Statement-1
Radiation involves transfer of heat by electromagnetic waves.
Statement-2
Electromagnetic waves do not required any material medium for propagation.

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Statement-1 is true, Statement-2 is true and Statement-2 is the correct explanation for Statement-1.
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Statement-1 is true, Statement-2 is true but Statement-2 is not the correct explanation for Staement-1.
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Statement-1 is true, Statement-2 is false.
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Statement-1 is false, Statement-2 is true.

The lowest attainable fahrenheit temperature is

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$-100^{\circ} F$
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$-459.4^{\circ} F$
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$-300^{\circ} F$
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$-373.2^{\circ} F$

Explanation

The lowest possible temperature, or absolute zero as it is called is

- {459.4}^{o} F

$-459.4^{o} F$ . By international agreement, absolute zero is taken as −273.15 degrees on the Celsius scale (International System of Units), which equals

- {459.4}^{o} F

$-459.4^{o} F$ degrees on the Fahrenheit scale

Hence, option B is correct.

For an ideal conductor, thermal resistance is :

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unity
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infinity
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zero
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1000

The process in which rate of transfer of heat is maximum is :

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conduction
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convection
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radiation
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in all these, heat is transferred with the same speed

Explanation

Step 1

$\textbf{Step 1}$ :

There are three modes of transmission of heat. They are Conduction, convection and radiation.

Conduction: In this mode of transmission. heat dissipates from one place to another by molecular vibration. It is relevant to solid only. Conduction needs a medium to transfer heat.

Convection: Heat is transferred from one place to another by the transfer of molecules. It happens only in liquids or gases. It also needs a medium to transfer heat.

Radiation: It transfers heat in the form of electromagnetic waves. It can heat any form of material. It doesn't need any medium for the transfer of heat.

Step 2

$\textbf{Step 2}$ :

We know that radiation travels with the speed of light. So, the rate of heat transfer is maximum in radiation in the form of electromagnetic radiation.

Thus option C is correct.

Which of the follwing is the smallest rise in temperature?

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$1^{\circ}F$
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$1K$
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$1^{\circ}C$
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All are of equal value

Explanation

There are 180 divisions in the Fahrenheit scale between the ice point and steam point while there are only 100 divisions in a Celsius scale.

And one scale division of a Kelvin scale is same as that of a Celsius scale.

So, $1^0F$ indicates a smaller rise in temperature than $1^0C$ and $1K$ .

If we place our hand below a lighted electric bulb. We feel warmer because of :

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convection
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radiation
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conduction
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both A and B

The temperature at which a body does not radiate energy

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$0^{0}$ C
0%
$0\ K$
0%
$273\ K$
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$4^{0}$ C

Explanation

Energy radiated becomes

0

$0$ only when absolute temperature becomes

0

$0$ .

Solids get heated by

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Conduction
0%
Convection
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Radiation
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None

Name the temperature scale used in S.I. system.

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Kelvin scale
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Celsius scale
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Fahrenheit scale
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All of the above

Which metal is a good conductor of heat?

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Gold
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Carbon
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Lead
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Alloys

The thermodynamic scale of temperature was given by

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Dewar
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Fahrenheit
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Kelvin
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Carnot

State true or false:

The more is the temperature difference of hot and cold body more slowly the heat flows from it into the cold body

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True
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False

Choose the correct experiment to demonstrate the transfer of heat by the process of conduction.

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Take two metal blocks of same size & shape and heat one of them to a considerable temperature, then allow both the blocks to touch each other, after a while, you will see the other block gets heated due to contact.
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Take two metal blocks of same size & shape and heat one of them to a considerable temperature, then keep the blocks separate, after a while you will see the other block gets heated due to contact.
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Take two metal blocks of same size & shape and heat one of them to a considerable temperature, then allow both the blocks to touch each other after the block get cooled down, after a while you will see the other block gets heated due to contact.
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None of above

The measure of degree of hotness or coldness of a body is called:

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Heat energy
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Celsius
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Kelvin
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Temperature

Complete the following sentences:
(a) Metals are ............. conductors of heat, while gases are ............ conductors of heat.
(b) Water is a ............ conductor of heat, while silver is a ................ conductor of heat.
(c) Silver is ............... conductor of heat than iron.

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(a) good, bad

(b) very poor, good

(c) a better
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(a) good, bad

(b) very good, good

(c) a better
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(a) bad, good

(b) very poor, good

(c) a better
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(a) good, bad

(b) very poor, bad

(c) a better

When two bodies at different temperatures are placed in thermal contact with each other, heat flows from the body at a higher temperature until they both acquire the same temperature. Assuming that there is no loss of heat to the surroundings, then:

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The heat gained by the hotter body will be equal to the heat lost by the colder body
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The heat gained by the hotter body will be less than the heat lost by the colder body
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The heat gained by the hotter body will be greater than the heat lost by the colder body
0%
The heat lost by the hotter body will be equal to the heat gained by the colder body.

The range of a clinical thermometer is

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0-100 $^0$ C
0%
32-214 $^0$ F
0%
0-1273 $^0$ C
0%
35-42 $^0$ C

Explanation

A clinical thermometer is used to measure the body temperature which normally remains between

35^{\circ}

$35^{\circ}$ C and

42^{\circ}

$42^{\circ}$ C.

The rise in temperature of a substance depends on

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the quantity of heat supplied
0%
the mass of the substance
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the nature of the substance
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all the above

A red hot brick is placed on an iron tripod stand which stands on a large block of copper. The brick loses heat by:

0%
conduction
0%
conduction and radiation
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conduction and convection
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conduction, convection, and radiation

Suppose a liquid in a container is heated at the top rather than at the bottom. What is the main process by which the rest of the liquid becomes hot ?

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Conduction
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Evaporation
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Sublimation
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None of these

At low temperatures ................. type of thermometer is used.

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mercury thermometer
0%
water thermometer
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alcohol thermometer
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thermometers cannot be used

Explanation

Alcohol thermometer.

Reason:

Alcohol expands uniformly.
It has a low freezing point ( $-115^oC$ ) therefore it is very suitable for the place where the temperature gets very low.
It is an easily available cheap liquid, which is safe to use.
Alcohol is cheaper than mercury, and if you break the thermometer, it is not toxic.

When you heat a bowl of water, we can observe that water starts circulating. This demonstrates:

0%
conduction
0%
convection
0%
radiation
0%
none

In the diagram shown, will the convection current be clockwise or anticlockwise on the left part of the figure?

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Anticlockwise
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Clockwise
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Will keep on changing
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Can't be said

The water in an open pond remains cool even in hot summer because

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of continuous evaporation of water
0%
water radiates heat more rapidly than the atmosphere
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water being bad conductor absorbs heat less rapidly than the atmosphere
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None of these

It is hotter over the top of fire than at the same distance on the sides because of:

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Convection of heat
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Conduction of heat
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Radiation of heat
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All of the above

Air is a good conductor of heat.

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True
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False

Which of the following is the coldest temperature possible?

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0K
0%
$0^{\circ}$ C
0%
$0^{\circ}$ F
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$-273^{\circ}$ F

The most commonly used thermometric substance is

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water
0%
alcohol
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mercury
0%
steam

Mud houses are cooler in summer and warmer in winter because

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mud is a good conductor of heat
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mud is a superconductor of heat
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mud is a bad conductor of heat
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none of these

Woollen sweaters keep us warm because:

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Wool is a poor conductor of heat
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Air is trapped in between the fibres
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Both A and B
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None of these

CBSE Questions for Class 7 Physics Heat Quiz 7 - MCQExams.com

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Practice Class 7 Physics Quiz Questions and Answers

CBSE Questions for Class 7 Physics Heat Quiz 7 - MCQExams.com

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Practice Class 7 Physics Quiz Questions and Answers

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