Tag: heat and heat transfer

Questions Related to heat and heat transfer

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

    Show answer
    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

    Show answer
    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

    Show answer
    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

    Show answer
    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

    Show answer
    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

    Show answer
    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

    Show answer
    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.

    Why are insulators important in an electrical circuit?

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

    1. They make the circuit safe to touch.

    2. Electricity will only flow through insulators.

    3. Light bulbs and buzzers are only made of insulating materials.

    4. All of the .above

    Show answer
    Correct Option: A
    Explanation:

    Insulators are used in circuits, as they don't conduct electricity, they are used for insulation of wire, switches, plugs, etc. So that circuit could be made shock free and safe to touch.

    Why are electrical plugs made of plastic?

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

    1. Plastic is stronger than all other materials.

    2. Plastic is a good electrical conductor.

    3. Plastic protects people from electricity.

    4. Only plastic can be made into the right shape for a plug

    Show answer
    Correct Option: C
    Explanation:

    Electrical plugs are made up of plastic because plastic protects people from electricity. As we know that plastic is an electrical insulator readily available and cheap. So as to make the plugs shock free, they are made up of plastic.

    Why is electrical wiring usually covered with a layer of plastic?

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

    1. To make it look pretty

    2. To help electricity flow along the wire

    3. To make it safe

    4. none of these

    Show answer
    Correct Option: C
    Explanation:

    Electrical wiring is usually covered with layer of plastic to make it safe. As we know that plastic is an electrical insulator and it is readily available and cheap. So as to insulate the electricity carrying wire, to make it shock free. It is covered with layer of plastic.