Tag: physics

Questions Related to physics

Which of the following qualities are best suited for handling a cooking utensil?

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. high specific heat and low thermal conductivity

  2. high specific heat and high thermal conductivity

  3. low specific heat and low thermal conductivity

  4. low specific heat and high thermal conductivity

Show answer
Correct Option: A
Explanation:

High specific heat means high energy required to increase temperature.
Hence for a given amount of energy, temperature would be less for high specific heat.
Low conductivity means heat is not conveyed to all portions of the conductor easily.
Hence, handling the instrument would be easy.

If pressure on a gas is increased from $P$ to $2P$, then its heat conductivity

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. increases

  2. decreases

  3. becomes zero

  4. remains unchanged

Show answer
Correct Option: D
Explanation:

Conductivity of gas does not depend on pressure.

Thermal conductivity of a metal rod depends on :

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. area of cross section

  2. temperature gradient

  3. time of flow of heat

  4. none of these

Show answer
Correct Option: D
Explanation:

Thermal conductivity is characteristic to the material and doesn't depend on any of the factors given.
In fact, heat flow depends on the factors given in options list.

Conduction is:

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. the process of transfer of heat which does not require any material medium

  2. the process of transferring heat from molecule to molecule, without the actual movement of molecules

  3. the process in which molecules conduct heat by moving from hotter regions to colder regions

  4. the process in which heat energy moves through the medium of protons

Show answer
Correct Option: B
Explanation:

Conduction is defined as the process of transferring heat from molecule to molecule, without the actual movement of molecules.

The coefficient of thermal conductivity of a metallic rod does not depend upon :

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. the length of the rod

  2. the cross-sectional area of the rod

  3. the temperature difference between the ends of the rod

  4. the nature of the metal

Show answer
Correct Option: A,B,C
Explanation:

Coefficient of $Thermal$ $Conductivity$ is the internal property of the metal and is independent of all the $external$ properties of the material.

So Coefficient of $Thermal$ $Conductivity$ is independent of dimensions, temperatures and other external factors too. It only depend on nature of material.

Conduction is ,

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. the process of transfer of heat which does not require any material medium

  2. the process of transferring heat from molecule to molecule, with out any movement of molecules

  3. the process in which molecules conduct heat by moving from hotter regions to colder regions

  4. the process in which heat energy moves through the medium of protons

Show answer
Correct Option: B
Explanation:

Conduction is the process by which heat or electricity is directly transmitted through the material of a substance without movement of the material.

It is warmer to have two thin blankets than to have single thick blanket because:

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. Thick blankets cannot give more warmth

  2. Two blankets allow more heat to pass through them

  3. Air between the two blankets is a good conductor of heat

  4. Air between the thin blankets does not allow heat to pass through it since it is a bad conductor

Show answer
Correct Option: D
Explanation:

Air is bad conductor of heat, so it does not allow the heat to pass through, while the single thick blanket is a better conductor of heat so it is less effective.

In which mode of transfer of heat molecules pass on heat energy to neighbouring molecules without actually moving from their positions?

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. convection

  2. radiation

  3. conduction

  4. none of these

Show answer
Correct Option: C
Explanation:
Conduction is the mode of heat transfer of heat molecules pass on heat energy to neighbouring molecules without actually moving from their positions.
Conduction is the transfer of heat from one substance to another by direct contact without mixing of masses.

In a steady state the temperature of the ends A and B of a 20 cm long rod AB is 100$^o$C and 0$^o$C. The temperature at the point c distant 9 cm from a is :

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $45^o$C

  2. $55^o$C

  3. $60^o$C

  4. $65^o$C

Show answer
Correct Option: B
Explanation:
Temperature increasing per unit length $=\cfrac{100-0}{20}=5^oC/cm$
Temperature at $9cm$ from $a \\ =100^oC-(5^oC/cm\times 9cm) \\ =55^oC$

Sea and land breezes are caused because of :

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. convection

  2. cyclones

  3. rains

  4. conduction

Show answer
Correct Option: A
Explanation:

All wind is caused by a pressure gradient. In the case of land or sea breeze, the pressure gradient is due to the different heating and cooling rates of the area.

Lake or sea breeze and land breeze are on a comparatively small scale when viewing meteorological events. This is important to note because large scale heating and small scale heating work differently. In the case of small scale heating, the increase in heat causes an increase in volume which in turn lowers the pressure in that area.
In the morning the land heats up much faster than the water. This eventually results in a pressure gradient with a lower pressure on the land due to the quicker heating. Air moves from the water to the land in the form of a sea breeze.

After sunset, the land cools much quicker than the water. As a result, the volume of the air over the water is higher and the pressure decreases. Ar then moves over the water as a land breeze.