Tag: transfer of heat

Questions Related to transfer of heat

A cotton sheet is ironed with hot electricity. How is energy transferred through the metal base of the iron to the sheet?

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. by conduction only

  2. by convection only

  3. by radiation only

  4. by convection and radiation only

Show answer
Correct Option: A
Explanation:
Conduction occurs when two objects at different temperatures are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature.
The iron and cotton sheet is in contact with each other so, there is conduction between them.

Energy transformation while ironing clothes takes out their wrinkles and makes them smooth. This takes the heat, which is one type of energy. In the iron, electrical energy is used, and it is transformed into heat energy.

In the following solids thermal conductivity is maximum for :

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. copper

  2. aluminium

  3. gold

  4. silver

Show answer
Correct Option: D
Explanation:

This is a knowledge based question; also remember that copper is used in electrical wiring only because it is cheaper than silver; copper has lower conductivity than silver.

Two layers of cloth of equal thickness provide warmer covering than a single layer of cloth of double the thickness, because they :

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. behave like a thermos

  2. have lesser thickness

  3. allow heat from atmosphere to the body

  4. enclose between them a layer of air

Show answer
Correct Option: D
Explanation:

Air is a bad conductor of heat, hence if layer of air is isolated between two layers of cloth, warmer covering will be provided than if only one layer of cloth, where only body is isolated from surrounding air by cloth. 

Thermoflasks and doors of refrigerators have two layered structure with an insulator in between so as:

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. to allow more heat to pass through it

  2. not to let heat flow through it

  3. to make it stronger

  4. to beautify it

Show answer
Correct Option: B
Explanation:

Insulator between the two layers prevent the heat exchange.

Mercury is generally used in thermometer because it has a

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. High fluidity

  2. High density

  3. High coefficient of expansion

  4. High specific heat

Show answer
Correct Option: C
Explanation:

Most metals are good conductors of heat and they are solids at room temperature. Mercury is the only one in liquid state at room temperature. It's used in thermometers because it has high coefficient of expansion. Hence, the slightest change in temperature is notable when it's used in a thermometer.

Which of the following is a good conductor of heat?

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. Plastic

  2. Mercury

  3. Water

  4. Alcohol

Show answer
Correct Option: B
Explanation:

Mercury is categorized under metasl and we know that metals conduct heat better than non-metals.

So mercury is the answer.

State whether given statement is True or False
To prevent heat conduction to our hands, handle of cooking vessels are made of bad conductors.

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. True

  2. False

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Correct Option: A
Explanation:

Good conductor will transfer the heat from vessel's handle to our hands and let our hands burn. So, bad conductor of heat, materials is used for manufacturing of vessel's handle.

What type of conductor should we used to make water pipes in cold countries?

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. Good conductor

  2. Poor conductor or bad conductor

  3. Material does not help in such cases

  4. None of the above

Show answer
Correct Option: B
Explanation:

Poor conductor should be used, so that they will not allow heat to pass from water inside the pipe to outside atmosphere to prevent water from freezing. It will help pipes from busting.

State whether given statement is True or False
Woollen yard is a bad conductor of heat. 

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Woollen sweaters keeps us warm in winter as the air gets trapped in woollen yard.

On a cold day when a room temperature is $15^oC$, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of $15^oC$, because

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. metals have higher thermal capacity than plastics

  2. plastics have a lower density than metals

  3. metals are good conductor of heat

  4. plastics have a higher thermal conductivity than metals

Show answer
Correct Option: C
Explanation:

On a cold day when a room temperature is $15^oC$, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of $15^oC$ because metals are good conductor of heat, so they could absorb and release heat in a better way than insulators.