Tag: transfer of heat

Questions Related to transfer of heat

a corked bottle full of water when frozen will break because.

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. The volume of water increases on freezing

  2. The volume of water decreases on freezing

  3. The bottle contracts on freezing

  4. Glass is a bad conductor of heat

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Correct Option: A
Explanation:
A corked bottle of water on being frozen at $0^{\circ}$ undergoes anomalous expansion of water between $4^{\circ}$ and $0^{\circ}$ wherein density of water increases on cooling , causing expansion due to orderly hydrogen bonding, this increasing volume cracks the bottle.
$Density=\cfrac{Mass}{Volume}$
$\Rightarrow D\propto \cfrac{1}{V}$
$\Rightarrow D\uparrow\Rightarrow V\downarrow$

Read the given statements and select the correct option.
Statement 1: An iron ball at ${35}^{o}C$ is dropped in a mug containing water at $305.15K$. Then the heat will flow from the water to the iron ball.
Statement 2: In convection, heated molecules of a liquid themselves move to carry heat from the hot region to the cold region.

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. Both statement 1 and 2 are true and statement 2 is the correct explanation of statement 1

  2. Both statement 1 and 2 are true and statement 2 is not the correct explanation of statement 1

  3. Statement 1 is true but statement 2 is false

  4. Statement 1 is false and statement 2 is true

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Correct Option: D
Explanation:

${35}^{o}C$ is equivalent to $(273.15+35)308.15K$. So iron ball is at higher temperature and heat will flow from iron ball to the water.

In a room contain air , heat can go from one place to another

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. By condition only

  2. by convection only

  3. By radiation only

  4. By all the three modes

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Correct Option: D

Which of the following is a good conductor of heat?

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. Steel

  2. Glass

  3. Wood

  4. Rubber

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Correct Option: A
Explanation:

Steel being an alloy of metals, it has free electrons in its atoms. They start moving along with the heat flow and help in the conduction of heat. All metals are good conductors. The other three being non-metals, do not have free electrons. Hence they are bad conductors

Heat travels much faster in insulators than in conductors.

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. True

  2. False

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Correct Option: B
Explanation:
The statement if false, heat travels much faster in insulators than in conductors.
Heat travels faster in conductor. Insulators donot even conduct heat, When heat is consumed by the conductor, it has 3 modes of transfer of heat conduction, convection and radiation.

Which of the following is/are bad conductors of heat?

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. Glass

  2. Aluminium

  3. Iron

  4. Wood

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Correct Option: A,D
Explanation:

All metals are good conductors while non-metals are bad conductors of heat.

Name a metal among the following having highest heat conductivity .

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. Silver

  2. Copper

  3. Aluminium

  4. Brass

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Correct Option: A
Explanation:
Following are the thermal conductivities of the following metals and alloys: ( in $wK/m$ )
$Silver-430 \\ Copper-400 \\ Aluminium-235 \\ Brass-109$
Order of thermal (heat) conductivity:
$Silver \gt Copper \gt Aluminium \gt Brass$
So, Silver has highest thermal conductivity

When we touch a steel rod and a paper simultaneously, we feel that the rod is colder because:

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. iron being a good conductor conducts more heat from our body

  2. paper being a good conductor conducts more heat from our body

  3. more heat flows from the iron to our body

  4. more heat flows from the paper to our body

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Correct Option: A
Explanation:

When we touch a steel rod and a paper simultaneously in winter, we feel the rod is comparatively colder because steel being a good conductor of heat, heat from our hand flows to steel but there is no transfer of heat from our hand to paper as it is an insulator of heat. So we don't feel cold when we touch a paper but we do when we touch a steel rod.

A good insulator of heat is

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. copper

  2. mercury

  3. trapped air

  4. iron

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Correct Option: C
Explanation:

A thermal conductor is a material that allows energy in the form of heat, to be transferred within the material, without any movement of the material itself. Eg. Metals.

An insulator is a material that does not allow a transfer of electricity or energy. Materials that are poor thermal conductors can also be described as being good thermal insulators.Eg. trapped air

Which of the following statement is true?

physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

  1. Metals are bad conductors of heat

  2. In gases, heat is transferred by conduction

  3. In conduction, molecules move from hotter to colder parts transmitting energy

  4. Metals conduct heat better than the gases.

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Correct Option: D
Explanation:
Metals conduct heat better than gases.
Order of conduction of heat
Solid $\gt$ Liquid $\gt$ Gas