Tag: conduction

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Questions Related to conduction

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 would normally be the best conductor?

  1. Copper

  2. Glass

  3. Steel

  4. Silver
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $20^oC$
$62.1\times 10^6 \gt 59.8\times 10^6 \gt 6.21\times 10^6$
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

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

  1. A piece of gravel.

  2. A rubber.

  3. A crayon

  4. Scissors made of iron
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

 Pure Water is an insulator.

  1. True

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

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

The outermost electrons are __________ and are called conduction electrons :

  1. not free to move in the atom

  2. bound to the protons

  3. static

  4. able to go to nearby atoms
Reveal answer Fill a bubble to check yourself
D Correct answer
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.
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

Which material is a best conductor?

  1. silver

  2. porcelain

  3. rubber

  4. gold
Reveal answer Fill a bubble to check yourself
A Correct answer
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 ($44.2\times 10^6 siemens/m$)
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

Which metal is a good conductor of heat?

  1. Gold

  2. Mercury

  3. Lead

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


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

Mud houses are cooler in summer and warmer in winter because

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

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

In case of conductors and insulators, if an electric field is applied then conduction current density$\vec{(J)}$ is:

  1. in the direction of electron flow.

  2. in the direction of proton flow.

  3. in the direction of electric field.

  4. against the direction of electric field.
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation
Current density, $\overrightarrow { J } =\cfrac { I }{ \overrightarrow { A }  } $
Current flows in direction of flow of protons. And the direction of electric field is in the direction of flow of electrons.
And the direction of current density is in the direction of proton flow, so from above statements, current density is also in the direction of electric field.
Multiple choice physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

Three rods of identical cross-sectional area and made from the same metal from the sides of an isosceles triangles ABC, right-angled at B. The point A and B are maintained at temperatures T and $(\sqrt{2})$T respectively. In the steady state, the temperature of the point C is $T _C$. Assuming that only heat conduction takes place, $T _C/T$ is?

  1. $\dfrac{1}{2\left(\sqrt{2}-1\right)}$

  2. $\dfrac{3}{\sqrt{2}+1}$

  3. $\dfrac{1}{\sqrt{3}\left(\sqrt{2}-1\right)}$

  4. $\dfrac{1}{\sqrt{2}+1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the steady-state heat flow condition (sum of heat currents at junction C is zero), the heat currents from A to C and B to C must balance. Given the geometry and thermal resistance, the calculation leads to the ratio 3/(sqrt(2)+1).