Tag: physics

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Questions Related to physics

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Which of the following is not a valid reason for using cotton clothes in Summer ?

  1. Cotton clothes attract cool air.

  2. Cotton clothes absorb sweat from the body.

  3. Cotton exposes the sweat to atmosphere for evaporation

  4. Cotton is light in weight.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

We wear cotton clothes during summer as cotton absorbs sweat from the body exposing to the atmosphere for easy evaporation. As we tend to sweat more during summer and cotton fabric absorb sweat and help body to cool down. Cotton allows better air circulation which helps to absorb and removing body moisture caused by sweat via evaporation cotton fabric is very light in weight.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Why do we wear cotton clothes in Summer ?

  1. Cotton is a bad conductor of heat and doesn't allow passage of warmer air near body.

  2. Cotton is a good conductor of heat and allows body heat to escape in the atmosphere.

  3. Cotton absorbs sweat from the body, exposing it to atmosphere for easy evaporation

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

We wear cotton clothes during summer as cotton absorbs sweat from the body, exposing to the atmosphere for easy evaporation. As we tend to sweat more during summer and cotton fabric absorbs sweat and help body to cool down. Cotton allows better air circulation which helps to absorb and removing body moisture caused by sweat via evaporation.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Which of the following is a wrong pair of clothes worn during a particular season ?

  1. Cotton clothes during summer

  2. Woolen clothes during winter

  3. Dark colored clothes during summer

  4. Polyester raincoats during Rainy season
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dark coloured clothes during summer is a wrong pair of clothes. As during summer, heat present in the atmosphere and surrounding is too much. And when dark colored clothes are the worm, as we know dark color absorbs more heat than any other color. So it will increase the heat felt by our body during summer.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Wool is used in making garments used in winter because

  1. Wool is a good conductor of heat

  2. Wool is a bad conductor of heat

  3. Air, trapped in between the wool fibres, prevents the flow of heat from our body to the cold surroundings.

  4. Both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Wool is used in making garments used in winter because wool is bad conductor of heat; it insulates the body from the surrounding. And the air which is trapped in between the wool fibers; prevents the flow of heat from our body to the cool surrounding. As air is the bad conductor of heat too it also insulates the body with wool.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Which of the following fabrics is preferred for winter garments ?

  1. Nylon

  2. Cotton

  3. Wool

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

Wool is the fabric that is preferred for winter garments. As wool is bad conductor of heat. It insulates the body from the surrounding. And the air which is trapped in between the wool fibers; it prevents the flow of heat from our body to cool surrounding.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Which of the following is not a reason for using woolen clothes in Winter ?

  1. Wool is an insulator of heat.

  2. It traps a layer of air in its fabric.

  3. Air being an insulator doesn't allow body heat to escape into the atmosphere.

  4. All the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Reason behind using woolen clothes during winter is that wool is the bad conductor of heat, it insulates the body from the surrounding. And the air which is trapped between woolen fabrics, prevents the flow of heat from the body as air is a bad conductor of heat too. So as a result the heat present in the body remains trapped in the body, it can't escape to atmosphere.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

How does air trapped by the woolen fabric help ?

  1. Air is a good conductor of heat and allows warm air to come near body

  2. Air is a bad conductor of heat and allows body heat to escape into atmosphere

  3. Air is a bad conductor of heat and doesn't allow body heat to escape into atmosphere

  4. Air is a good conductor of heat and doesn't allow cool air to come near body.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Air trapped by the woolen fabric help us during winter. As air is bad conductor of heat and doesn't allow body heat to escape into atmosphere. The heat stored inside the body does not goes out as wool and air acts as a layer of insulator. And body heat is not escaped from the body.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Which of the following circular rods (given radius r and length l), each made of the same material and whose ends are maintained at the same temperature will conduct most heat?

  1. $r=r _0;l=l _0$
  2. $r=2r _0;l=l _0$
  3. $r=r _0;l=2l _0$
  4. $r=2r _0;l=2l _0$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Heat is given by $H=KA\Delta \theta _x=K\pi r^2 \dfrac{\Delta \theta} {l}$

For option B the value of $H$ will be more.

Multiple choice physics electro-magnetism applications of electromagnets

A permanent magnet in the shape of a thin cylinder of length $10$cm has magnetisation (M) $=10^6$A $m^{-1}$. It's magnetization current $I _M$ is?

  1. $10^5$A
  2. $10^6$A
  3. $10^7$A
  4. $10^8$A
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given:

 The length of the thin cylinder is $10\ cm$.
The magnetization of the magnet is $10^6 A/m$

The magnetization current is given by:
$I _M=M\times l$

$I _M=10^6\times 0.1$

$\Rightarrow10^5\ A$