Tag: transfer of heat

Questions Related to transfer of heat

State whether given statement is True or False
Innermost electrons are free to move :

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

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
False
Innermost electrons are not free to move because they are tightly held by the attractive force by the protons present in the nucleus of the element. Only outermost electrons are free to move in conductors.

When electrons in a material are free to move, the material is:

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

  1. an insulator

  2. a conductor

  3. a semiconductor

  4. none of these

Show answer
Correct Option: B
Explanation:
When electrons in a material are free to move, the material is a conductor.
As only conductors have free electrons present in the outermost shell which are mobile and behave as charge carriers and are conduction electrons.

What is NOT an example of an insulator in the kitchen?

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

  1. An oven mitt

  2. A wooden spoon

  3. Pots and pans

  4. A plastic measuring cup

Show answer
Correct Option: C
Explanation:

Pots and pans are NOT example of insulator, they are conductors of heat, if it was not so; they could not be used for cooking of food. And they are used for cooking; so they are conductors.

Which of the following would normally be the best conductor?

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

  1. Copper

  2. Glass

  3. Steel

  4. Silver

Show answer
Correct Option: D
Explanation:
Among copper, glass, silver and steel, glass is non-metal i.e. insulator; so it has least conductivity.
Conductivity order:
Silver $\gt$ Copper $\gt$ Steel
(in $siemens/m$) at $20^oC$
$62.1\times 10^6 \gt 59.8\times 10^6 \gt 6.21\times 10^6$

Which of these could be used to complete an electrical circuit?

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

  1. A piece of gravel.

  2. A rubber.

  3. A crayon

  4. Scissors made of iron

Show answer
Correct Option: D
Explanation:

Scissors made of iron could be used to complete an electrical circuit. As iron is a metal and conductor so can conduct electricity easily. And others are non-metals. So they could not conduct electricity and can't complete the circuit.

 Pure Water is an insulator.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Pure water consists of no impurities; impurities such as salts of $Mg,Ca,Na$ are behaving here as charge carriers but since they are not present; there are no ions. They are neutral water molecules. So pure water do not conduct electricity.

The outermost electrons are __________ and are called conduction electrons :

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

  1. not free to move in the atom

  2. bound to the protons

  3. static

  4. able to go to nearby atoms

Show answer
Correct Option: D
Explanation:
The outermost electrons are able to go to nearby atoms and are called conduction electrons.
Yes the outermost shell electrons are able to go to nearby atoms only during bond formation (ionic bond). They are free or mobile electrons because of that they conduct electricity so they are called conduction electrons.

Which material is a best conductor?

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

  1. silver

  2. porcelain

  3. rubber

  4. gold

Show answer
Correct Option: A
Explanation:
Out of silver, porcelain, rubber, and gold; porcelain and rubber are non-metals i.e. insulators. So
Now out of silver and gold conductivity of silver ($62.1\times 10^6 siemens/m$) is more than that of gold ($44.2\times 10^6 siemens/m$)

Which metal 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. Gold

  2. Mercury

  3. Lead

  4. Alloys

Show answer
Correct Option: A
Explanation:
As metals contain free electrons, it transfers the energy given in the form of heat rapidly but in non-metals, it takes time to heat. Gold is metal so it is a good conductor of heat and mercury, lead, alloys are non-metals so they are poor conductors of heat.


Mud houses are cooler in summer and warmer in winter because

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

  1. mud is a good conductor of heat

  2. mud is a superconductor of heat

  3. mud is a bad conductor of heat

  4. none of these

Show answer
Correct Option: C
Explanation:

Mud is a bad conductor of heat. It does not allow the heat to transfer from house to atmosphere in winter and atmosphere to house in summer.