Tag: fundamentals of heat transfer

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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.

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

In conductors, electrons can flow because their

    1. ions are free

    2. protons are free

    3. electrons are free and mobile

    4. negative ions are free
    Reveal answer Fill a bubble to check yourself
    C Correct answer
    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.

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

    An insulator is a non-metallic substance which :

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

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

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

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

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

    Poor conductors of electricity consist of

    1. silver

    2. aluminum

    3. distilled water

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

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

    Why is electrical wiring usually made from copper?

    1. Because copper is shiny.

    2. Because copper conducts electricity.

    3. Because copper is not magnetic

    4. none of these
    Reveal answer Fill a bubble to check yourself
    B Correct answer
    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.

    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 materials is an electrical conductor?

    1. Silver

    2. Silver-coloured plastic

    3. Cork

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