## Temperature and Heat – Class 11 | Chapter – 11 | Physics Short Notes Series PDF for NEET & JEE

Temperature and Heat: Temperature and heat are closely related but distinct concepts. Temperature is a measure of the average kinetic energy of the particles in a substance. In simpler terms, it is a measure of how hot or cold something is. Temperature is measured in units such as Celsius (°C), Fahrenheit (°F), or Kelvin (K). Heat, on the other hand, is the energy transferred between two objects or systems due to a temperature difference. Heat flows from a hotter object to a cooler object until thermal equilibrium is reached. The SI unit of heat is joule (J).

What is Heat?

Heat is a form of energy that is transferred between objects as a result of a difference in temperature. Heat always flows from hotter to cooler objects until thermal equilibrium is reached, meaning both objects have the same temperature. Heat can be transferred by three mechanisms: conduction, convection, and radiation.

Conduction is the transfer of heat through direct contact between two objects. For example, if you touch a hot stove, heat is transferred from the stove to your hand through conduction.

Convection is the transfer of heat through the movement of fluids, such as air or water. For example, when you heat a pot of soup on the stove, the hot soup rises and cooler soup sinks, creating a convection current that distributes heat throughout the pot.

Radiation is the transfer of heat through electromagnetic waves, such as infrared radiation. For example, the sun radiates heat to the Earth through space.

Heat is measured in units of energy, such as Joules or calories, and is commonly measured using a thermometer.

Heat Transfer

Heat transfer is the movement of thermal energy from one object or system to another as a result of a temperature difference between them. Heat transfer can occur by conduction, convection, and radiation, as mentioned in my previous response.

Conduction occurs when heat energy is transferred through a material without any net movement of the material itself. Heat energy is transferred from one part of a material to another by collisions between neighboring molecules. Good conductors of heat, such as metals, transfer heat rapidly while poor conductors, such as plastics and gases, transfer heat more slowly.

Convection is the transfer of heat through the movement of fluids. When a fluid, such as a gas or a liquid, is heated, it expands and becomes less dense, causing it to rise. Cooler fluid then moves in to take its place, creating a convection current that transfers heat energy from one part of the fluid to another.

Radiation occurs when heat energy is transferred through electromagnetic waves. These waves can travel through space and do not require a medium to transfer heat energy. Examples of radiation include sunlight, which warms the Earth, and heat lamps, which emit infrared radiation.

Heat transfer is important in many fields, including engineering, physics, and chemistry, and is essential for many industrial processes and everyday applications such as cooking, heating and cooling of buildings, and transportation.

What is Temperature?

emperature is a physical quantity that is used to describe the degree of hotness or coldness of an object or a system. It is a measure of the average kinetic energy of the particles in the system. In simpler terms, temperature is a measure of how fast the particles are moving in a substance or object.

Temperature is typically measured in units of degrees Celsius (°C), Fahrenheit (°F), or Kelvin (K). The Celsius and Fahrenheit scales are both based on the freezing and boiling points of water, while the Kelvin scale is based on the absolute zero temperature, which is the lowest possible temperature, where all particles have zero kinetic energy.

## Relationship between Temperature and Heat

The relationship between temperature and heat is expressed by the following equation:

Q = mcΔT

Where,

• Q is the amount of heat transferred
• m is the mass of the substance
• c is the specific heat capacity of the substance
• ΔT is the change in temperature

In other words, the amount of heat transferred depends on the mass of the substance, the specific heat capacity of the substance (which determines how much energy is required to raise the temperature of the substance), and the change in temperature.

Overall, while temperature and heat are related, they represent different concepts. Temperature is a measure of how hot or cold something is, while heat is the energy transferred between two objects due to a temperature difference.

## Difference between Temperature and Heat

The differences between Temperature and Heat are as follows:

Heat Temperature
Heat is the amount of energy stored in an object. Temperature is a measure of the thermal energy in a substance.
The SI unit of heat is Joules. The SI unit of temperature is Kelvin.
The other unit for measuring heat is Calories. The other units for measuring heat are Fahrenheit and Celsius.
The symbol of heat is Q. The symbol of temperature is T.
Heat stored in an object depends on the mass, temperature, and material of the object. Temperature depends on the average kinetic energy of the molecules or particles of a body.
Heat is measured by Calorimeter using the principle of calorimetry. Temperature is measured using a thermometer.
Two bodies with a similar amount of heat can differ in their temperature. Two bodies with a similar temperature can contain different amounts of heat energy.
When two bodies are in contact with each other, the sum of the heat energy of both objects would be the total heat energy. If two objects with different temperatures are in contact with each other, the resultant temperature will be the temperature between the two temperatures.
Heat has the ability to do work. Temperature is only used to measure the degree of heat.
Heat flows from hotter objects or regions to colder regions or objects. Temperature increases when there is more heat and decreases when cooled.

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