Tag: heat and heat transfer

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Questions Related to heat and heat transfer

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

Name a metal among the following having highest heat conductivity .

  1. Silver

  2. Copper

  3. Aluminium

  4. <span>Brass</span>
Reveal answer Fill a bubble to check yourself
A Correct answer
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
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

A good insulator of heat is

  1. copper

  2. mercury

  3. trapped air

  4. iron
Reveal answer Fill a bubble to check yourself
C Correct answer
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

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

Which of the following statement is true?

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Metals conduct heat better than gases.
Order of conduction of heat
Solid $\gt$ Liquid $\gt$ Gas
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

Which of the following is the very poor conductor of heat ?

  1. Water

  2. Metals

  3. Liquid other than water

  4. Steam
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water is the poor conductor among all. As it is liquid and liquids generally have low heat conductivity than solids. Tighter the molecules are held, more the vibrational energy can transfer between them, heat is no more than vibrating molecules. If we talk about steam, its molecules are less tightly held. But it's important to note that we are talking here of heat conductivity not convection or radiation and contact surface area with heat source.

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

Assertion (A): Woolen clothes keep the body warm in winter
Reason (R): Air is bad conductor of heat

  1. Both A and R are true,

  2. Both A and R are false

  3. Both A and R are true, R is correct explanation of A

  4. Both A and R are true, R is not correct explanation of A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Woollen clothes effectively separate the body from surrounding air by entrapping a layer of air.
Since both wool and air are bad conductors of heat on varying levels, it creates separation that keeps bodies warm.

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

A coin is dipped in the molten wax in a glass tube. When we heat the upper part of the glass tube, the wax around the coil will not melt because:

  1. Wax has a very high melting point

  2. Wax is a good conductor of heat

  3. Glass is a good conductor of heat

  4. Wax or glass are bad conductors
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Glass is a bad conductor of heat hence the heat from the upper part of the glass tube will not transfer easily to the lower part. Having said that, even wax is a bad conductor of heat and won't melt easily.