Thermal convection is the process of the transfer of heat through a fluid body, either in a liquid or gas state, by action of the movement of the fluid. This phenomenon occurs because the warmer and less-dense areas of the fluid rise while the cooler and dense ones sink, creating a circulating flowRead more
Thermal convection is the process of the transfer of heat through a fluid body, either in a liquid or gas state, by action of the movement of the fluid. This phenomenon occurs because the warmer and less-dense areas of the fluid rise while the cooler and dense ones sink, creating a circulating flow that helps distribute the heat, and some common phenomena including:
1. Atmospheric Circulation (Wind Patterns)
– Atmospheric circulation is primarily induced by unequal heating of the Earth’s surface by the Sun, which induces variations in temperature and pressure in the atmosphere. The warm air that is adjacent to the surface rises because of being less dense. The colder air from greater heights sinks downward, creating the mechanism of convection currents and subsequently wind. Wind patterns comprise trade winds, westerlies, and polar winds.
These currents move the air around, forming the basis for many weather conditions like cloud development, thunderstorms, and hurricanes.
2. Ocean Currents
– Convection in the oceans is an important mechanism for distributing heat around the globe. Warm water near the equator becomes less dense and rises, while colder water from the polar regions sinks. This circulation, called the “thermohaline circulation” or “global conveyor belt,” helps regulate Earth’s climate by transferring heat from the equator to the poles.
– This process affects the distribution of nutrients, impacts marine life, and is involved in climate phenomena such as El Niño.
3. Mantle Convection (Plate Tectonics)
– The mantle of the Earth is convective as heat from the core rises, cools, and sinks in a continuous cycle. This is what drives the motion of tectonic plates on the Earth’s surface, leading to earthquakes, volcanic eruptions, and mountain building.
– Mantle convection is one of the driving forces behind plate tectonics, which shapes the surface of the Earth over geological time.
4. Heating Systems (Radiators)
Many house heating systems work with radiators, using the principle of thermal convection for distributing heat through the room. The radiator will warm the surrounding air, expanding it and lowering its density, so it tends to rise upwards. Meanwhile, cooler air in the environment will sink in to replace this. This creates an ongoing cycle in which warm air is rising and cooler air is falling, circulating the heat throughout the room.
5. Convection in Liquids (Boiling Water)
As this water in a pot heats, the water toward the bottom has heated and reduced in density by rising up the sides to take its place by cooler, heavier water coming in from the top to displace it. By this means of convection circulation, it works to equal out the heating going on through each portion of this body of liquid eventually causing all water to attain this uniform temperature state that eventually it boils.
6. Volcanic Eruptions
– Convection currents in the Earth’s mantle can lead to the rise of molten rock, or magma, toward the Earth’s surface. When the pressure is sufficient, magma erupts through volcanoes, creating lava flows, ash clouds, and other volcanic phenomena.
– The process of mantle convection and magma movement is crucial to understanding the dynamics of volcanic activity.
7. Cloud Formation (Convection in the Atmosphere)
– In the atmosphere, convection is responsible for the formation of clouds. When warm air at the Earth’s surface rises, it cools as it ascends. If the air cools to the point where it reaches its dew point, condensation occurs, forming water droplets or ice crystals that make up clouds.
– This cycle may result in the formation of thunderstorms, provided that upward convection with warm air is strong enough.
8. Convection in the Outer Core of Earth (Formation of Magnetic Field)
The Earth’s outer core is made up of liquid iron and nickel, which is responsible for the generation of the Earth’s magnetic field through the dynamo effect. Heat from the inner core causes the molten metals to rise, cool, and sink, creating electric currents that produce the magnetic field protecting Earth from solar radiation.
Heat is a form of energy transferred from one body to another due to a temperature difference between them. It always flows from the body with higher temperature to the body with lower temperature. Heat causes a change in temperature, phase, or state of a substance. The amount of heat transferred deRead more
Heat is a form of energy transferred from one body to another due to a temperature difference between them. It always flows from the body with higher temperature to the body with lower temperature. Heat causes a change in temperature, phase, or state of a substance.
The amount of heat transferred depends on the mass of the substance, its specific heat capacity, or its ability to store heat, and the temperature change. Heat is measured in joules (J) in the SI system. Other units like calories are also used, where 1 calorie equals 4.18 joules.
Three main processes are through which heat transfer occurs: conduction – direct contact, convection – fluid movement, and radiation – energy transfer through electromagnetic waves. It is used in many natural phenomena and technological processes, including cooking, weather conditions, and heating industrial installations.
Work done in the stretching of a wire is described by the relation, W = (1/2) F * l Where, - Force applied is represented by F. - Elongation is depicted by l Thus, the work done will be Fl/2.
Work done in the stretching of a wire is described by the relation,
W = (1/2) F * l
Where,
– Force applied is represented by F.
– Elongation is depicted by l
Thus, the work done will be Fl/2.
When a load W is applied to a wire, it elongates by length l. However, when two weights W each are hung at the two ends of the wire over a pulley, the effective force applied on the wire is still 2W. This results in the wire elongating by 2l. Click here: https://www.tiwariacademy.com/ncert-solutionsRead more
When a load W is applied to a wire, it elongates by length l. However, when two weights W each are hung at the two ends of the wire over a pulley, the effective force applied on the wire is still 2W. This results in the wire elongating by 2l.
The coefficients of linear expansion (α), superficial expansion (β), and cubical expansion (γ) are interrelated based on the effect of temperature change on the length, area, and volume of a material. 1. Linear Expansion (α): The change in length (ΔL) for a material due to temperature change is giveRead more
The coefficients of linear expansion (α), superficial expansion (β), and cubical expansion (γ) are interrelated based on the effect of temperature change on the length, area, and volume of a material.
1. Linear Expansion (α):
The change in length (ΔL) for a material due to temperature change is given by:
ΔL = α L ΔT
where α is the coefficient of linear expansion, L is the original length, and ΔT is the temperature change.
2. Superficial Expansion (β):
The change in area (ΔA) for a material due to temperature change is given by:
ΔA = β A ΔT
where β is the coefficient of superficial expansion, A is the original area, and ΔT is the temperature change.
Since area is related to length by A = L², the relation between β and α is:
β = 2α
3. Cubical Expansion (γ):
The change in volume (ΔV) for a material due to temperature change is given by:
ΔV = γ V ΔT
where γ is the coefficient of cubical expansion, V is the original volume, and ΔT is the temperature change.
Since volume is related to length by V = L³, the relation between γ and α is:
γ = 3α
4. Relation between α, β, and γ:
Combining the equations above:
β = 2α and γ = 3α
So the relation between three coefficients of expansion is,
β = 2α and γ = 3α
The coefficient of linear expansion, denoted by α, is defined as the fractional change in length of the material for a unit change in temperature at constant pressure when the material is heated or cooled. Mathematically, it is defined as: α = (1/L) * (dL/dT) where α is the coefficient of linear expRead more
The coefficient of linear expansion, denoted by α, is defined as the fractional change in length of the material for a unit change in temperature at constant pressure when the material is heated or cooled.
Mathematically, it is defined as:
α = (1/L) * (dL/dT)
where
α is the coefficient of linear expansion,
L is the initial length of the material,
dL is the change in length,
dT is the change in temperature.
The units of α are per degree Celsius (°C⁻¹) or per Kelvin (K⁻¹).
Limits:
– α is nearly constant for most solids in a narrow range of temperature.
– The value of α increases with temperature for some materials but is constant for many solid materials within small variations in temperature.
The thermal expansion of a body is defined as the change in its dimensions, either length, area, or volume, when the temperature of the body is changed. When the temperature increases, the particles of the body move vigorously, which makes the body expand. Types of Thermal Expansion: 1. Linear ExpanRead more
The thermal expansion of a body is defined as the change in its dimensions, either length, area, or volume, when the temperature of the body is changed. When the temperature increases, the particles of the body move vigorously, which makes the body expand.
Types of Thermal Expansion:
1. Linear Expansion: Change in length of a solid body when heated.
Example: Expansion of a metal rod.
2. Apparent Expansion: Change in area of a body when heated.
Example: Expansion of metal sheet.
3. Volumetric Expansion: Change in volume of a body when heated.
Example: Expansion of a gas or liquid in a container.
A thermoelectric thermometer works on the principle of the thermoelectric effect, also known as the Seebeck effect. This effect occurs when two different metals are joined at two points and there is a temperature difference between them. The junctions of these metals generate a voltage that is propoRead more
A thermoelectric thermometer works on the principle of the thermoelectric effect, also known as the Seebeck effect. This effect occurs when two different metals are joined at two points and there is a temperature difference between them. The junctions of these metals generate a voltage that is proportional to the temperature difference.
In a thermoelectric thermometer, two dissimilar conductors (such as copper and iron) form a closed loop, and one of the junctions is exposed to the temperature to be measured while the other is kept at a reference temperature, usually at ice point. The difference in temperature between the junctions results in a thermoelectric potential difference (voltage) developing across the loop. The voltage is then measured and converted to temperature using a calibration curve.
The main advantage of thermoelectric thermometers is that they provide accurate temperature measurements over a wide range without moving parts, hence reliable and precise readings in applications.
The potential energy curve is the variation of the potential energy between atoms or molecules in a solid with respect to their separation distance and can be used to explain thermal expansion of solids. At absolute zero temperature, atoms in a solid are at their equilibrium positions where the poteRead more
The potential energy curve is the variation of the potential energy between atoms or molecules in a solid with respect to their separation distance and can be used to explain thermal expansion of solids.
At absolute zero temperature, atoms in a solid are at their equilibrium positions where the potential energy is at its minimum. With increasing temperature, atoms vibrate more violently and average separation between them increases because kinetic energy of atoms increases with temperature.
The curve of potential energy shows that the atoms are moving apart, and this is when the potential energy increases. The system comes to a new equilibrium position in which the atoms are at a slightly larger separation, thus causing the expansion of the solid. The amplitude of atomic vibrations increases with temperature, which leads to an overall expansion of the material.
In solids, the thermal expansion is uniform in all directions, linear, superficial, or cubical depending on the nature of the solid and its temperature change.
It is the fractional change in the surface area of a substance for a unit change in temperature, when heated or cooled at constant pressure. It is defined mathematically as: α = (1/A) * (dA/dT) where, - α is the coefficient of superficial expansion - A is the initial surface area - dA is the changeRead more
It is the fractional change in the surface area of a substance for a unit change in temperature, when heated or cooled at constant pressure. It is defined mathematically as:
α = (1/A) * (dA/dT)
where,
– α is the coefficient of superficial expansion
– A is the initial surface area
– dA is the change in surface area
– dT is the change in temperature.
The units of α are per degree Celsius (°C⁻¹) or per Kelvin (K⁻¹).
Describe some of the phenomena which are based on thermal convection.
Thermal convection is the process of the transfer of heat through a fluid body, either in a liquid or gas state, by action of the movement of the fluid. This phenomenon occurs because the warmer and less-dense areas of the fluid rise while the cooler and dense ones sink, creating a circulating flowRead more
Thermal convection is the process of the transfer of heat through a fluid body, either in a liquid or gas state, by action of the movement of the fluid. This phenomenon occurs because the warmer and less-dense areas of the fluid rise while the cooler and dense ones sink, creating a circulating flow that helps distribute the heat, and some common phenomena including:
1. Atmospheric Circulation (Wind Patterns)
– Atmospheric circulation is primarily induced by unequal heating of the Earth’s surface by the Sun, which induces variations in temperature and pressure in the atmosphere. The warm air that is adjacent to the surface rises because of being less dense. The colder air from greater heights sinks downward, creating the mechanism of convection currents and subsequently wind. Wind patterns comprise trade winds, westerlies, and polar winds.
These currents move the air around, forming the basis for many weather conditions like cloud development, thunderstorms, and hurricanes.
2. Ocean Currents
– Convection in the oceans is an important mechanism for distributing heat around the globe. Warm water near the equator becomes less dense and rises, while colder water from the polar regions sinks. This circulation, called the “thermohaline circulation” or “global conveyor belt,” helps regulate Earth’s climate by transferring heat from the equator to the poles.
– This process affects the distribution of nutrients, impacts marine life, and is involved in climate phenomena such as El Niño.
3. Mantle Convection (Plate Tectonics)
– The mantle of the Earth is convective as heat from the core rises, cools, and sinks in a continuous cycle. This is what drives the motion of tectonic plates on the Earth’s surface, leading to earthquakes, volcanic eruptions, and mountain building.
– Mantle convection is one of the driving forces behind plate tectonics, which shapes the surface of the Earth over geological time.
4. Heating Systems (Radiators)
Many house heating systems work with radiators, using the principle of thermal convection for distributing heat through the room. The radiator will warm the surrounding air, expanding it and lowering its density, so it tends to rise upwards. Meanwhile, cooler air in the environment will sink in to replace this. This creates an ongoing cycle in which warm air is rising and cooler air is falling, circulating the heat throughout the room.
5. Convection in Liquids (Boiling Water)
As this water in a pot heats, the water toward the bottom has heated and reduced in density by rising up the sides to take its place by cooler, heavier water coming in from the top to displace it. By this means of convection circulation, it works to equal out the heating going on through each portion of this body of liquid eventually causing all water to attain this uniform temperature state that eventually it boils.
6. Volcanic Eruptions
– Convection currents in the Earth’s mantle can lead to the rise of molten rock, or magma, toward the Earth’s surface. When the pressure is sufficient, magma erupts through volcanoes, creating lava flows, ash clouds, and other volcanic phenomena.
– The process of mantle convection and magma movement is crucial to understanding the dynamics of volcanic activity.
7. Cloud Formation (Convection in the Atmosphere)
– In the atmosphere, convection is responsible for the formation of clouds. When warm air at the Earth’s surface rises, it cools as it ascends. If the air cools to the point where it reaches its dew point, condensation occurs, forming water droplets or ice crystals that make up clouds.
– This cycle may result in the formation of thunderstorms, provided that upward convection with warm air is strong enough.
8. Convection in the Outer Core of Earth (Formation of Magnetic Field)
The Earth’s outer core is made up of liquid iron and nickel, which is responsible for the generation of the Earth’s magnetic field through the dynamo effect. Heat from the inner core causes the molten metals to rise, cool, and sink, creating electric currents that produce the magnetic field protecting Earth from solar radiation.
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Explain the concept of heat.
Heat is a form of energy transferred from one body to another due to a temperature difference between them. It always flows from the body with higher temperature to the body with lower temperature. Heat causes a change in temperature, phase, or state of a substance. The amount of heat transferred deRead more
Heat is a form of energy transferred from one body to another due to a temperature difference between them. It always flows from the body with higher temperature to the body with lower temperature. Heat causes a change in temperature, phase, or state of a substance.
The amount of heat transferred depends on the mass of the substance, its specific heat capacity, or its ability to store heat, and the temperature change. Heat is measured in joules (J) in the SI system. Other units like calories are also used, where 1 calorie equals 4.18 joules.
Three main processes are through which heat transfer occurs: conduction – direct contact, convection – fluid movement, and radiation – energy transfer through electromagnetic waves. It is used in many natural phenomena and technological processes, including cooking, weather conditions, and heating industrial installations.
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A wire fixed at the upper end stretches by length l by applying a force F. The work done in stretching is
Work done in the stretching of a wire is described by the relation, W = (1/2) F * l Where, - Force applied is represented by F. - Elongation is depicted by l Thus, the work done will be Fl/2.
Work done in the stretching of a wire is described by the relation,
See lessW = (1/2) F * l
Where,
– Force applied is represented by F.
– Elongation is depicted by l
Thus, the work done will be Fl/2.
A wire elongates by l mm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be (in mm)
When a load W is applied to a wire, it elongates by length l. However, when two weights W each are hung at the two ends of the wire over a pulley, the effective force applied on the wire is still 2W. This results in the wire elongating by 2l. Click here: https://www.tiwariacademy.com/ncert-solutionsRead more
When a load W is applied to a wire, it elongates by length l. However, when two weights W each are hung at the two ends of the wire over a pulley, the effective force applied on the wire is still 2W. This results in the wire elongating by 2l.
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Derive the relation between α, β and γ.
The coefficients of linear expansion (α), superficial expansion (β), and cubical expansion (γ) are interrelated based on the effect of temperature change on the length, area, and volume of a material. 1. Linear Expansion (α): The change in length (ΔL) for a material due to temperature change is giveRead more
The coefficients of linear expansion (α), superficial expansion (β), and cubical expansion (γ) are interrelated based on the effect of temperature change on the length, area, and volume of a material.
1. Linear Expansion (α):
The change in length (ΔL) for a material due to temperature change is given by:
ΔL = α L ΔT
where α is the coefficient of linear expansion, L is the original length, and ΔT is the temperature change.
2. Superficial Expansion (β):
The change in area (ΔA) for a material due to temperature change is given by:
ΔA = β A ΔT
where β is the coefficient of superficial expansion, A is the original area, and ΔT is the temperature change.
Since area is related to length by A = L², the relation between β and α is:
β = 2α
3. Cubical Expansion (γ):
The change in volume (ΔV) for a material due to temperature change is given by:
ΔV = γ V ΔT
where γ is the coefficient of cubical expansion, V is the original volume, and ΔT is the temperature change.
Since volume is related to length by V = L³, the relation between γ and α is:
γ = 3α
4. Relation between α, β, and γ:
Combining the equations above:
β = 2α and γ = 3α
So the relation between three coefficients of expansion is,
β = 2α and γ = 3α
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Define coefficient of liner expansion. Write an expression for it. Give its limits.
The coefficient of linear expansion, denoted by α, is defined as the fractional change in length of the material for a unit change in temperature at constant pressure when the material is heated or cooled. Mathematically, it is defined as: α = (1/L) * (dL/dT) where α is the coefficient of linear expRead more
The coefficient of linear expansion, denoted by α, is defined as the fractional change in length of the material for a unit change in temperature at constant pressure when the material is heated or cooled.
Mathematically, it is defined as:
α = (1/L) * (dL/dT)
where
α is the coefficient of linear expansion,
L is the initial length of the material,
dL is the change in length,
dT is the change in temperature.
The units of α are per degree Celsius (°C⁻¹) or per Kelvin (K⁻¹).
Limits:
– α is nearly constant for most solids in a narrow range of temperature.
– The value of α increases with temperature for some materials but is constant for many solid materials within small variations in temperature.
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What is meant by thermal expansion of a body? What are the different types of thermal expansion?
The thermal expansion of a body is defined as the change in its dimensions, either length, area, or volume, when the temperature of the body is changed. When the temperature increases, the particles of the body move vigorously, which makes the body expand. Types of Thermal Expansion: 1. Linear ExpanRead more
The thermal expansion of a body is defined as the change in its dimensions, either length, area, or volume, when the temperature of the body is changed. When the temperature increases, the particles of the body move vigorously, which makes the body expand.
Types of Thermal Expansion:
1. Linear Expansion: Change in length of a solid body when heated.
Example: Expansion of a metal rod.
2. Apparent Expansion: Change in area of a body when heated.
Example: Expansion of metal sheet.
3. Volumetric Expansion: Change in volume of a body when heated.
Example: Expansion of a gas or liquid in a container.
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Briefly describe the working principle of a thermoelectric thermometer.
A thermoelectric thermometer works on the principle of the thermoelectric effect, also known as the Seebeck effect. This effect occurs when two different metals are joined at two points and there is a temperature difference between them. The junctions of these metals generate a voltage that is propoRead more
A thermoelectric thermometer works on the principle of the thermoelectric effect, also known as the Seebeck effect. This effect occurs when two different metals are joined at two points and there is a temperature difference between them. The junctions of these metals generate a voltage that is proportional to the temperature difference.
In a thermoelectric thermometer, two dissimilar conductors (such as copper and iron) form a closed loop, and one of the junctions is exposed to the temperature to be measured while the other is kept at a reference temperature, usually at ice point. The difference in temperature between the junctions results in a thermoelectric potential difference (voltage) developing across the loop. The voltage is then measured and converted to temperature using a calibration curve.
The main advantage of thermoelectric thermometers is that they provide accurate temperature measurements over a wide range without moving parts, hence reliable and precise readings in applications.
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Explain thermal expansion of solids on the basis of the potential energy curve.
The potential energy curve is the variation of the potential energy between atoms or molecules in a solid with respect to their separation distance and can be used to explain thermal expansion of solids. At absolute zero temperature, atoms in a solid are at their equilibrium positions where the poteRead more
The potential energy curve is the variation of the potential energy between atoms or molecules in a solid with respect to their separation distance and can be used to explain thermal expansion of solids.
At absolute zero temperature, atoms in a solid are at their equilibrium positions where the potential energy is at its minimum. With increasing temperature, atoms vibrate more violently and average separation between them increases because kinetic energy of atoms increases with temperature.
The curve of potential energy shows that the atoms are moving apart, and this is when the potential energy increases. The system comes to a new equilibrium position in which the atoms are at a slightly larger separation, thus causing the expansion of the solid. The amplitude of atomic vibrations increases with temperature, which leads to an overall expansion of the material.
In solids, the thermal expansion is uniform in all directions, linear, superficial, or cubical depending on the nature of the solid and its temperature change.
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See lesshttps://www.tiwariacademy.com/ncert-solutions/class-11/physics/chapter-10/
Define coefficient of superficial expansion and give its units.
It is the fractional change in the surface area of a substance for a unit change in temperature, when heated or cooled at constant pressure. It is defined mathematically as: α = (1/A) * (dA/dT) where, - α is the coefficient of superficial expansion - A is the initial surface area - dA is the changeRead more
It is the fractional change in the surface area of a substance for a unit change in temperature, when heated or cooled at constant pressure. It is defined mathematically as:
α = (1/A) * (dA/dT)
where,
– α is the coefficient of superficial expansion
– A is the initial surface area
– dA is the change in surface area
– dT is the change in temperature.
The units of α are per degree Celsius (°C⁻¹) or per Kelvin (K⁻¹).
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See lesshttps://www.tiwariacademy.com/ncert-solutions/class-11/physics/chapter-10/