0

Uses of good and poor conductors in daily life - class-VI

Description: uses of good and poor conductors in daily life
Number of Questions: 41
Created by:
Tags: temperature and heat clothes - our necessity evs - i thermal properties of matter heat properties of bulk matter physics heat transfer transfer of heat
Attempted 0/41 Correct 0 Score 0

If we keep pop corn in a pressure cooker on a flame, heat is transferred from flame to corn by :

  1. Conduction

  2. Radiation

  3. Convection

  4. None


Correct Option: A
Explanation:

The direct contact of cooker and corn is an example of conduction.

The molecules of medium vibrate about their mean positions during heat transfer in the process of

  1. Conduction

  2. Radiation

  3. Convection

  4. None


Correct Option: A
Explanation:

The molecules of medium transfer heat as they vibrate about mean position in conduction.
The molecules of medium absorb heat, they rise and other molecules of medium come to take their place convection
In radiation, medium does not play role.

Air is a bad conductor of heat because:

  1. it's molecules are in continuous contact with each other.

  2. it's molecules are not in continuous contact with each other

  3. it's molecules absorb all the heat

  4. it's molecules are moving randomly due to Brownian motion


Correct Option: B
Explanation:
Air is a bad conductor of heat because it's molecules are not in continuous contact with each other.
Air molecules are too far to disperse heat energy to one another efficiently. Heat is conducted by molecules and atoms that are very closely bonded together and vibrating at high frequency.

.................. surface absorbs more heat than any other surface under identical conditions.

  1. White & Shiny

  2. White & Rough 

  3. Black & Rough

  4. Yellow & Shiny


Correct Option: C
Explanation:
Black & rough surface absorbs more heat than any other surface under identical conditions.
Black surface absorbs all the radiations more easily than any surface as its absorptivity is $1$.

The heat transfer in air is poor because

  1. it take place mainly due to convection

  2. it take place mainly due to conduction

  3. it take place mainly due to radiation

  4. all of the above


Correct Option: A
Explanation:

Air is a gas and its molecules are far apart from each other. So, this is not a good condition for conduction. Also, air being a non-metal doesn't have free electrons for conduction. Hence option B is not applicable.

C is also not applicable because radiation doesn't need any medium. Air being a fluid, convection can take place through it. But convection is not a very fast mode of transfer of heat.

Seema is planning a trip to Kashmir this summer. Which of the following clothes should she definitely pack?

  1. Denim Jacket

  2. Leather pants

  3. Woolen sweater

  4. Cotton shirt


Correct Option: C
Explanation:

She must pack the woolen sweater, because even in summer; Kashmir's climate will definitely too much cool. As wool is good insulator of heat; it insulates body from the surrounding. And the air which is trapped between woolen fabrics. It prevents the flow of heat from the body; as air is also bad conductor of heat. So as a result the heat present in the body remains trapped in the body; it can't escape to atmosphere.

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.


Correct Option: A
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.

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


Correct Option: C
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.

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


Correct Option: C
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.

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


Correct Option: D
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.

Which of the following fabrics is preferred for winter garments ?

  1. Nylon

  2. Cotton

  3. Wool

  4. Silk


Correct Option: C
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.

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


Correct Option: D
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.

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.


Correct Option: C
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.

When a metal conductor connected to left gap of a meter bridge is heated, the balancing point.

  1. Shifts towards right

  2. Shifts towards left

  3. Remains unchanged

  4. Remains at zero


Correct Option: A
Explanation:

When resistor is heated its resistance increases hence the balancing point will shift towards right.

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. $r=2r _0;l=2l _0$


Correct Option: B
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.

A shining metallic ball with a small black spot on its surface is heated to very high temperature and then quickly taken to a dark room. Then.

  1. Both appear equally bright

  2. The spot appears brighter than the ball

  3. The spot appears darker than the ball

  4. Both are invisible in the dark room


Correct Option: B

If object A and object B has no transfer of heat, then they both are in

  1. Catalytic

  2. Thermal equilibrium

  3. Expansion

  4. None


Correct Option: B
Explanation:

$Object \ A \rightleftharpoons Object\ B$
Both are at same temperature or there is not temperature difference between them.

Good conductor of heat is

  1. Hydrogen

  2. Oxygen

  3. Nitrogen

  4. None


Correct Option: D
Explanation:

All of them are gases, which are not good conductors of heat.

Air is a _______ conductor of electricity.

  1. Good

  2. Bad

  3. Both

  4. None


Correct Option: B
Explanation:

All gases are poor conductor of heat. Air is a very poor conductor of heat.

Air is a good conductor of heat. True or false.

  1. True

  2. False


Correct Option: B
Explanation:
False
Air is bad conductor of heat. It is due to the air trapped between the cotton molecules which gives warmth on taking quilt in winter It is due to air molecules trapped between wool fabrics which provide warmth to body during winter season.

Wearing black clothes in summer is more preferable. True or false.

  1. True

  2. False


Correct Option: B
Explanation:
False
Wearing black clothes in summer is not preferable as during summer there is more heat present in the atmosphere and black clothes absorb more heat comparatively. So, black clothes are not preferable during summer.

State whether given statement is True or False
Two thin blankets are more warmer than one thick blanket

  1. True

  2. False


Correct Option: A
Explanation:
The blanket do not insulate; actually air insulates.
Air is trapped in the space between two thin blankets. Since air is insulator of heat, it prevents the escape of body heat. The air can't pass deeper and the layers will stop the air in two thin blankets where as there are no layers and air can pass deeper in one thick blanket. That's why two thin blankets are usually warmer than one thick blanket.

Good conductors of heat is

  1. Copper

  2. Water

  3. Wood

  4. Glass


Correct Option: A
Explanation:

Substances become bad conductors of heat when they contain a large number of free electrons. This is because the electrons contained in atom of these elements are not closely bond to nucleus.

Why tubes of a boiler are covered with layer of asbestos?

  1. Asbestos is bad conductor of heat

  2. Asbestos is good conductor of heat

  3. Neither A nor B

  4. None


Correct Option: A
Explanation:

The tubes are covered with asbestos layer in order to prevent heat less by conduction.

Which of the following materials is used to make clinical thermometer?

  1. Magnet

  2. Mercury

  3. Copper

  4. Titanium


Correct Option: B
Explanation:

Mercury because it has low freezing point and high boiling point so it can be used over wide range of temperature.

The thermometric liquid should be a

  1. Bad conductor of heat

  2. Good conductor of heat

  3. It should be of high freezing point

  4. It should be of low boiling point


Correct Option: B
Explanation:

The thermometric liquid should be of high MP and BP and good conductor of heat, so it quickly absorbs heat to obtain temperature of object.

A cold steel serving spoon is dipped in hot mushroom soup. It transfers heat to its other end by process of

  1. Convection

  2. Conduction

  3. Radiation

  4. None


Correct Option: B
Explanation:

Conduction: Process of transfer of heat by contacting one body with other. In this process, heat transfer takes place without moving the particles.

Metal floors cool more than a wood floor in winters because:
  1. Metal conducts heat more readily than wood

  2. Wood conducts heat more readily than metal

  3. Metal has a higher specific heat than wood

  4. The temperature of the wood is higher than the temperature of the metal

  5. The temperature of the metal is higher than the temperature of the wood


Correct Option: A
Explanation:

Metals are good conductor of heat whereas wood does not conduct heat at all.

Thus in winters, metal floors cool more than a wood floor.

Which of the following is a good conductor of heat?

  1. Water and glass

  2. Plastic and copper

  3. Copper and glass

  4. Copper


Correct Option: D

__and__are good conductors of heat

  1. Silver, Copper

  2. Wood,Plastic

  3. Glass,Paper

  4. Pure water,Iron


Correct Option: A
Explanation:
Silver and copper are good conductors of heat.
$\because$ Silver and copper are only metals present there and as we know metals have conductivity of heat and electricity than non-metal and metalloids. So, silver and copper are god conductors of heat.

State the correct statement

  1. When we heat an object, it becomes hot

  2. When we heat an object, it expands in size

  3. When we heat an object, it changes its such such as water boils to form water vapour

  4. All of them are true


Correct Option: D
Explanation:

When we heat an object, it changes its shape, nature and it becomes hot, the temperature increases due to movement of atoms.

Bad conductor of heat is

  1. Copper

  2. Steel

  3. Silver

  4. None


Correct Option: D
Explanation:

All of them, being metals, are good conductors.

The ............ the conductor, the more rapidly does heat transfer takes place.

  1. better

  2. worse

  3. thinner

  4. thicker


Correct Option: A
Explanation:

The better the conductor, the more rapidly does heat transfer takes place .


Better conductor means more thermal conductivity; more the thermal conductivity; more rapidly the heat transfer takes place.

The reason for providing copper bottoms in steel pans is :

  1. aesthet, carly looks good

  2. that copper is better conductor than steel

  3. that copper is not a good conductor than steel

  4. None of the above 


Correct Option: B
Explanation:

Copper bottoms are provided in steel pans because copper is better conductor of heat than steel.

Thermal conductivity of copper is highest ($38600w/mK$) while that of steel is lowest ($1245w/mK$).

Four rods of same material but with different radii and lengths are used to connect two reservoirs of heat with the same temperature difference. Which one will conduct more heat

  1. r=1 cm, 1=1 cm

  2. r=1 cm, 1= 2 cm

  3. r= 1 cm, $1=\frac{1}{2}m$

  4. $r=\frac{1}{2}cm$, $1=\frac{1}{2}m$


Correct Option: C

Which of the following arrangements is correct on the basis of conductivity of materials?

  1. Silver > copper > aluminium > tungsten

  2. Silver > aluminium > copper > tungsten

  3. Copper > silver >tungsten> aluminium

  4. Silver > tungsten > copper > aluminium


Correct Option: C

What will be the conductivity of pure silicon crystal at 300 K temperature if  electron cottoer pair at this temperature is $ 1.072 \times 10^{10} /cm^3 $ and $ \mu _n = 1350 cn^2 /V-s and \mu _p = 480 cm^2/ V-s $ ?

  1. $ 3.14 \times 10^{-4} mho /cm $

  2. $ 3.14 \times 10^{-5} mho /cm $

  3. $ 3.14 \times 10^{-6} mho /cm $

  4. $ 3.14 \times 10^{3} mho /cm $


Correct Option: A

 Inorder to have a difference of $25 \,cm$ in their length at all temperatures, the lengths of iron and copper rods at $0^o C$ are $(\alpha _{iron} = 12 \times 10^{-6} {^oC}^{-1}, \alpha _{copper} = 17 \times 10^{-6} {^oC}^{-r})$

  1. $85 \,cm, 110 \,cm$

  2. $50 \,cm, 25 \,cm$

  3. $85 \,cm, 60 \,cm$

  4. $60 \,cm, 85 \,cm$


Correct Option: C

The heat capacity of a body depends on 

  1. the heat given

  2. the temperature rasied

  3. the mass of the body

  4. the material of he body.


Correct Option: C

In a steady state of thermal conduction, temperature of the ends $A$ and $B$ of a $20cm$ long rod are $100^oC$ and $0^oC$, respectively. What will be the temperature of the rod at a distance of $6cm$ from the end $A$ of the rod?

  1. $-30^oC$

  2. $70^oC$

  3. $5^oC$

  4. None of the above


Correct Option: B

Which of the following is a bad conductor of heat?

  1. Gold

  2. Wood

  3. Silver

  4. Iron


Correct Option: B
- Hide questions