Tag: fundamentals of heat transfer

Questions Related to fundamentals of heat transfer

Easy to shape materials like ceramics are used as

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

  1. conductors.

  2. insulators.

  3. electrodes.

  4. catalysts.

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Correct Option: B
Explanation:
Glass, tiles, pottery, porcelain, brick, cement etc. are ceramics.
They are obviously insulators of heat.

Overhead cables are insulated from pylons through

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

  1. plastic.

  2. ceramics and glass.

  3. rubber.

  4. PVC.

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Correct Option: B
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.

In conductors outer electrons :

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

  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

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Correct Option: A
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.

In conductors, electrons can flow because their

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

    1. ions are free

    2. protons are free

    3. electrons are free and mobile

    4. negative ions are free

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    Correct Option: C
    Explanation:

    In conductors, electrons can flow because their electrons are free and mobile metals have free electrons present in outermost orbit i.e. they are mobile in nature. This is the fact due to which they could produce electricity.

    An insulator is a non-metallic substance which :

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

    1.  allows heat to pass through it

    2. has extremely low resistance to the flow of charge through them

    3. has extremely high resistance to the flow of charge through them

    4. increases current in the circuit

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    Correct Option: C
    Explanation:

    An electrical insulator is a material whose internal electric charges do not flow freely because of extremely high resistance. Very little electric current will flow through it under the influence of an electric field.

    Metals are good conductors of electricity than non-metals because:

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

    1. Metals have free electrons which can move from atom to atom easily

    2. Non-metals have free electrons which can move from atom to atom easily

    3. Metals have bound electrons which cannot move easily

    4. Non-metals have bound electrons which cannot move easily

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    Correct Option: A,D
    Explanation:

    Metals have free electrons which can move from atom to atom easily, whereas non-metals do not, their electrons are 'bound' meaning they cannot move easily. That's why metal are usually good conductors than non-metals.

    Poor conductors of electricity consist of

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

    1. silver

    2. aluminum

    3. distilled water

    4. copper

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    Correct Option: C
    Explanation:

    Pure water or distilled water doesnot conduct electricity but tap water, rain water or sea water conduct electricity. For electricity to travel through a liquid movement of charge must take place through the liquid. In tap water, rain water or sea water, there are impurities such as salt of $Na,Mg \; and \; Ca$. They behave as the charge carriers for conduction of electricity. But in distilled water there are no impurities i.e. no ions. There are only neutral water molecules. So, distilled water doesnot conduct electricity.

    Why is electrical wiring usually made from copper?

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

    1. Because copper is shiny.

    2. Because copper conducts electricity.

    3. Because copper is not magnetic

    4. none of these

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    Correct Option: B
    Explanation:

    Copper is usually used for copper wiring because copper conducts electricity. Because electrical conductivity of copper is good enough and it is cheap too. So it is used in wiring.

    Which of the following materials is an electrical conductor?

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

    1. Silver

    2. Silver-coloured plastic

    3. Cork

    4. Rubber

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    Correct Option: A
    Explanation:
    As we know that generally, metals are conductors and non-metals are insulators. That is metal conduct electricity more than that of non-metal.
    SIlver is the only metal present in the list, so it is the only electrical conductor.
    All others are non-metals.

    Which of the following materials is an electrical insulator?

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

    1. Aluminium

    2. Gold

    3. Rubber

    4. all of these

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    Correct Option: C
    Explanation:
    As we know that generally, non-metals are insulators and metals are conductors.
    As rubber is the only non-metal in the list, so it is an electrical insulator.