Physics · Science General

Heat Transfer Mechanisms

828 Questions

Heat Transfer Mechanisms deal with the movement of thermal energy through conduction, convection, and radiation. It involves practical applications like ocean heat storage and atmospheric heating. These fundamental physics concepts are frequently asked in general science sections.

Thermal conductionHeat convectionThermal radiationSpecific heatStates of matter

Heat Transfer Mechanisms Questions

Multiple choice chemistry non-metals introduction to non-metals occurence of metals occurrence of metals and non metals

Heat conduction is the property of __________.

  1. Non-metals

  2. Metals

  3. Metalloids

  4. All of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Heat conduction is the property of metals. In metals, valance electron is free to flow among the atoms. Because of that metals are such good conductors of electricity. These electrons can also carry energy in the form of heat and thus the metals are conductors of heat.


Hence, the correct option is $B$

Multiple choice movement in plants living world of plants - plant physiology biology

Thermonastic movement is related to

  1. Light

  2. Touch

  3. Chemical

  4. High temperature
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nastic movement is non-directional movement shown by plant part in response to external stimuli. Thermonastic movement is response shown by plant part to high temperature. Photonastic movement is the response to light. Thigmonastic movement is the response to touch. Chemonastic movement is the response to the chemical.

Thus, the correct answer is option D.

Multiple choice evs the unique world of insects and animals sleeping time animal senses sense organs in animals sense organs in humans

The following detects infrared energy (heat)

  1. chemoreceptors

  2. photoreceptors

  3. mechanoreceptors

  4. thermoreceptors
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

(A)Chemoreceptor - Receptor that responds to chemicals.

(B)Photoreceptor - Receptor that responds to light.
(C)Mechanoreceptor - Receptor that responds to pressure, position, acceleration.
(D)Thermoreceptor -Receptor that responds to heat.
So, the correct option is 'Thermoreceptor'.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

Name a medium which is a good insulator of heat.

  1. Still (or trapped) air

  2. Oil

  3. Steam

  4. solid copper
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer 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?

  1. by conduction only

  2. by convection only

  3. by radiation only

  4. by convection and radiation only
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

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

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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. 

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

A hetaed smooth metallic body is allowed to cool in air. Which of the following statements about its heat loss is incorrect?

  1. Convection currents in the air aid the process of heat loss.

  2. Conduction is the main mode of heta loss as the body is a good conductor of heat

  3. The rate of heat loss by thermal radiation is increased due to its metallic surface.

  4. The rate of heat loss decreases as the temperature of teh body nears room temperature
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The statement that the rate of heat loss by radiation is increased due to a metallic surface is incorrect because metallic surfaces (especially smooth ones) have low emissivity, which reduces radiative heat loss. Convection and conduction are standard modes of heat transfer, and heat loss rate naturally decreases as the body approaches ambient temperature.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

A sphere, a cube and a thin circular plate, all of same material and same mass, are initially heated to same high temperature. Choose the correct statement.

  1. The plate will cool fastest and cube the slowest

  2. The sphere will cool faster and cube and the slowest

  3. The plate will cool faster and sphere the slowest

  4. The cube will cool fastest and plate the slowest.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cooling rate is proportional to the surface area to volume ratio (A/V). For a fixed mass and material, the object with the largest surface area will have the highest rate of heat loss. A thin circular plate has the highest surface area, while a sphere has the lowest surface area for a given volume.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

There are two hollow spheres made of different materials, one with double the radius and one fourth wall thickness of the other are filled with ice. If the time taken for melting the ice completely in larger sphere is $25$ minutes and that for smaller sphere is $16$ minutes, the ratio of the thermal conductivity of the larger sphere to the smaller sphere is :

  1. $4:5$
  2. $5:4$
  3. $25:8$
  4. $8:25$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Smaller sphere

Radius $\to \dfrac{R}{2}$. wall thickness $\to 4d$

Larger sphere
Radius $\to R$, wall thickness $\to d$

Vol of ice in smaller sphere $= \dfrac{4}{3} \pi \left(\dfrac{R}{2} - 4d\right)^3$

$m _S = $ Mass of ice in smaller sphere $=\rho _{ice} \times \dfrac{4}{3}\pi \left(\dfrac{R}{2} - 4d\right)^3$

$m _L = $ Mass of ice in larger sphere $= \rho _{ice} \times \dfrac{4}{3} \pi (r-d)^3$

Heat required to melt $m _S = m _sL = \dfrac{4}{3}\pi \left(\dfrac{R}{2} 4d\right)^3\times \rho _{ice} \times L = Q _s$        ...(i)

Heat required to melt $m _L = m _l L = \dfrac{4}{3} \pi (R-d)^3 \times \rho _{ice} \times L = Q _L$          ...(ii)

$\dfrac{Q}{t} = \dfrac{KA}{x} (\Delta T)$

$\dfrac{Q _s}{16} = \dfrac{K _s4\pi\left(\dfrac{R}{2}\right)^2}{4d}\Delta T$      ...(for small sphere)      ...(1)

$\dfrac{A _L}{25} = \dfrac{K _24\pi R^2}{d}\Delta T$        ...(for large sphere)   ....(2)

Dividing eq(1)  by eq(2)
$\therefore \dfrac{Q _L}{25} \times \dfrac{16}{Q _s} = \left(\dfrac{K _L}{K _S}\right)\dfrac{4\pi R^2\Delta T\times 4d}{4\pi\left(\dfrac{R}{2}\right)^2\Delta T \times d}$

$\therefore \dfrac{Q _L}{Q _S} \times \dfrac{16}{25} = \left(\dfrac{K _L}{K _S}\right)\times 16$

but $\dfrac{Q _L}{Q _S} = \dfrac{(R-d)^3}{\left(\dfrac{R}{2}-4d\right)^3}$

here $R > > d$,

$\therefore \dfrac{Q _L}{Q _S} = \dfrac{R^3}{\left(\dfrac{R}{2}\right)^3} = 8$

$\therefore \dfrac{8}{25} = \dfrac{K _L}{K _S}$

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

Read the given statements and select the correct option.
Statement 1: An iron ball at ${35}^{o}C$ is dropped in a mug containing water at $305.15K$. Then the heat will flow from the water to the iron ball.
Statement 2: In convection, heated molecules of a liquid themselves move to carry heat from the hot region to the cold region.

  1. Both statement 1 and 2 are true and statement 2 is the correct explanation of statement 1

  2. Both statement 1 and 2 are true and statement 2 is not the correct explanation of statement 1

  3. Statement 1 is true but statement 2 is false

  4. Statement 1 is false and statement 2 is true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

${35}^{o}C$ is equivalent to $(273.15+35)308.15K$. So iron ball is at higher temperature and heat will flow from iron ball to the water.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

In a room contain air , heat can go from one place to another

  1. By condition only

  2. by convection only

  3. By radiation only

  4. By all the three modes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a room with air, heat transfer occurs via conduction (through the air and objects), convection (movement of air currents), and radiation (electromagnetic waves). All three modes contribute to heat transfer in this environment.

Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

When we touch a steel rod and a paper simultaneously, we feel that the rod is colder because:

  1. iron being a good conductor conducts more heat from our body

  2. paper being a good conductor conducts more heat from our body

  3. more heat flows from the iron to our body

  4. more heat flows from the paper to our body
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When we touch a steel rod and a paper simultaneously in winter, we feel the rod is comparatively colder because steel being a good conductor of heat, heat from our hand flows to steel but there is no transfer of heat from our hand to paper as it is an insulator of heat. So we don't feel cold when we touch a paper but we do when we touch a steel rod.

Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

Which of the following is the very poor conductor of heat ?

  1. Water

  2. Metals

  3. Liquid other than water

  4. Steam
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water is the poor conductor among all. As it is liquid and liquids generally have low heat conductivity than solids. Tighter the molecules are held, more the vibrational energy can transfer between them, heat is no more than vibrating molecules. If we talk about steam, its molecules are less tightly held. But it's important to note that we are talking here of heat conductivity not convection or radiation and contact surface area with heat source.

Multiple choice physics transfer of heat heat and heat transfer heat energy transfer heat energy transfers fundamentals of heat transfer conduction

Assertion (A): Woolen clothes keep the body warm in winter
Reason (R): Air is bad conductor of heat

  1. Both A and R are true,

  2. Both A and R are false

  3. Both A and R are true, R is correct explanation of A

  4. Both A and R are true, R is not correct explanation of A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Woollen clothes effectively separate the body from surrounding air by entrapping a layer of air.
Since both wool and air are bad conductors of heat on varying levels, it creates separation that keeps bodies warm.