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

State True or False :
Good conductors of heat are also good conductors of electricity. 

  1. True

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

Usually, good conductors of heat are also good conductors of electricity. However, this is not always true. One of the exceptions is mica. Mica is good conductor of heat but bad conductor of electricity.

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

Conductors become hot easily because they have:

  1. high specific capacity

  2. low specific heat capacity

  3. high freezing point

  4. low freezing point
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Specific heat capacity is the amount of heat required to raise the temperature of a unit mass by one degree. Materials with low specific heat capacity require less energy to increase their temperature, thus they become hot easily.

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

In general, metals have very low :

  1. Boiling Point

  2. Freezing Point

  3. Melting Point

  4. Specific Heat Capacity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In conduction, heat is transferred by the vibrations of molecules. The density of conductors is large, it means molecules are close to each other, because of that they can easily transfer the heat quickly through the whole conductor, therefore unit mass of conductors require small heat to raise their temperature through $1^{o}$ i.e. conductors have very low specific heat. 

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

Specific heat capacity is ______ for conductors of heat and _______ for insulators of heat.

  1. low, low

  2. low, high

  3. high, high

  4. high, low
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Q=ms\Delta T$,

where 
$Q: \text{the amount of heat delivered to a body}$
$m: \text{mass of the body}$
$s: \text{specific heat capacity of the body}$
$\Delta T: \text{Change in temperature of the body}$

If $Q\ \text{and}\ m$ are constant, 
$\Delta T \propto \dfrac{1}{s}$

So for small $s, \Delta T$ is more and hence it is better conductor of heat.

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

Graphite is a conductor of electricity because

  1. it has free valence electrons.

  2. it is a non-metal form of Carbon.

  3. it is an allotrope of Carbon.

  4. Both A and B.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Graphite is a conductor of electricity because it has free valence electrons.
Graphite displays the property of both metal and non-metal. Like a metal, graphite is good conductor of electricity due to mobility of electrons in outer valence shells.
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

Overhead cables are insulated from pylons through

  1. plastic.

  2. ceramics and glass.

  3. rubber.

  4. PVC.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Examples of ceramics are clay, bricks, tiles, glass, and cement.
Overhead cable is insulated from pylons through ceramics and glass.
The overhead power lines that are supported by pylons are not covered in insulating materials. However, ceramics or glass insulators are fitted between pylons and wires. This stops electricity flowing down the metal pylons to the ground, where it could hurt or even kill people or animals.
Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

In conductors outer electrons :

  1. are not tightly bound to the nucleus

  2. are tightly bound to the nucleus

  3. never becomes free electrons

  4. are always free to move
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Conductors can easily conduct electricity because they are loosely bound to the nucleus and they are not engaged in chemical bonding. Conductors have free electrons.