Tag: heat energy transfers

Questions Related to heat energy transfers

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.

A material that does NOT let electricity pass through it is called ...

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

  1. an electrical conductor

  2. an electrical insulator

  3. an electrical appliance

  4. none of these

Show answer
Correct Option: B
Explanation:
A material that does not allow to electricity to pass through, it is called an electrical insulator.
They do not have free electrons present in their outer most shell which would work as charge carriers for conduction of electricity.

Materials that allow electrons to flow through them are known as

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

  1. Insulator

  2. Conductors

  3. Electrolytes

  4. Bases

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Correct Option: B
Explanation:

Materials that allow electrons to flow through them are known as conductors because they consist of free electrons.

Which of these is a good electrical conductor?

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

  1. Water

  2. Sweat

  3. The human body

  4. All of the above

Show answer
Correct Option: D
Explanation:
Water is a good electrical conductor but not distilled water. Tap water, Sea water, rain water etc. conduct electricity as they consists of impurities; salts of $Ca, \; Mg,\; Na$ which behave as charge carriers.

Sweat conducts electricity although it is mainly water, it still consists of lot of minerals, lactic acid, urea; in short, it is an ionic liquid (electrolyte)

Human body consists of $75 $% of water and also consists of many minerals and salts. So human body also conducts electricity.

State whether given statement is True or False
In a superconductor, electricity will flow for a long time and then stop.

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

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
False
Superconductors are those materials which have exactly zero resistance and expulsion of magnetic flux occurs when they are cooled below certain temperatures.

State whether given statement is True or False
Innermost electrons are free to move :

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

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
False
Innermost electrons are not free to move because they are tightly held by the attractive force by the protons present in the nucleus of the element. Only outermost electrons are free to move in conductors.

When electrons in a material are free to move, the material is:

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

  1. an insulator

  2. a conductor

  3. a semiconductor

  4. none of these

Show answer
Correct Option: B
Explanation:
When electrons in a material are free to move, the material is a conductor.
As only conductors have free electrons present in the outermost shell which are mobile and behave as charge carriers and are conduction electrons.

What is NOT an example of an insulator in the kitchen?

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

  1. An oven mitt

  2. A wooden spoon

  3. Pots and pans

  4. A plastic measuring cup

Show answer
Correct Option: C
Explanation:

Pots and pans are NOT example of insulator, they are conductors of heat, if it was not so; they could not be used for cooking of food. And they are used for cooking; so they are conductors.

Which of the following would normally be the best conductor?

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

  1. Copper

  2. Glass

  3. Steel

  4. Silver

Show answer
Correct Option: D
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 $20^oC$
$62.1\times 10^6 \gt 59.8\times 10^6 \gt 6.21\times 10^6$

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

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

  1. A piece of gravel.

  2. A rubber.

  3. A crayon

  4. Scissors made of iron

Show answer
Correct Option: D
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.