Tag: physics

Questions Related to physics

The vacuum created in simple barometer is known as __________ vacuum
physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure devices to measure pressure

  1. Newton's

  2. Barometric

  3. Torricellian

  4. Archimedes

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Correct Option: C
Explanation:

A simple barometer or a mercury barometer has a glass tube closed at one end with an open mercury-filled reservoir at the base. The weight of the mercury creates a vacuum in the top of the tube known as Torricellian vacuum. 

The liquid used in simple barometer is

physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure devices to measure pressure

  1. Glycerine

  2. Kerosene

  3. Mercury

  4. Halogen

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Correct Option: C
Explanation:

A mercury barometer, or a simple barometer, has a glass tube, of length approximately 100cm, closed at one end with an open mercury-filled reservoir at the base. The weight of the mercury creates a vacuum in the top of the tube known as Torricellian vacuum. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir. High atmospheric pressure places more force on the reservoir, forcing mercury higher in the column. Low pressure allows the mercury to drop to a lower level in the column by lowering the force placed on the reservoir. 

A geyser heats water flowing at the rate of 4 litre per minutes from 30 C to 85 C. If the geyser operates on gas burner then the amount of heat used per minute is :

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

  1. $9.24\times { 10 }^{ 5 }$J

  2. $6.24\times { 10 }^{ 7 }$J

  3. $9.24\times { 10 }^{ 7 }$J

  4. $6.24\times { 10 }^{ 5 }$J

Show answer
Correct Option: A
Explanation:

For one minute

$H=mC\theta$
$=4kg\times 4200\times55\=924000J\=9.24\times 10^5j$

A 2 m long wire of resistance 4 ohm and diameter 0.64 mm is coated with plastic insulation of thickness 0.06 mm, when a current of 5 ampere flows through the wire, find the temperature difference across the insulation in steady state if $k=0.16\times { 10 }^{ -2 }cal/\left( cm{ C }^{ 0 }sec \right) $ 

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

  1. ${ 3 }^{ \circ }C$

  2. ${ 2 }^{ \circ }C$

  3. ${ 4 }^{ \circ }C$

  4. ${ 1 }^{ \circ }C$

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Correct Option: A

M g of ice at ${ 0 }^{ \circ  }C$ is mixed with M g of water at ${ 10 }^{ \circ  }C.$ The final temperature is

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

  1. ${ 8 }^{ \circ }C$

  2. ${ 6 }^{ \circ }C$

  3. ${ 4 }^{ \circ }C$

  4. ${ 0 }^{ \circ }C$

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Correct Option: A

Name a medium which is a good insulator of heat.

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

  1. Still (or trapped) air

  2. Oil

  3. Steam

  4. solid copper

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Correct Option: A
Explanation:
Trapped(still) air is good insulator.
Thermal conductivity of air is small as compared to solid and liquid. Eg- glass conducts 30 times more power per unit distance per unit temperature than air.
The less dense the material, the less thermal conductivity. And gas(air) is least dense than solid and liquid.

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

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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

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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

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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.