“Thermal Equilibrium and Zeroth Law” MHT-CET Class 12 Physics Crash Course | Chapter Thermodynamics
In this session G.S. Khairnar discussed the theory and MCQ’s of “Thermal Equilibrium and Zeroth Law”. The session will be useful for all the aspirants of MHT-CET 2022. The session will be in Marathi and English.
Thermal Equilibrium and Zeroth Law:-
Hello dear students, we are familiar that heat is transferred from point of higher temperature to lower temperature till the difference between the two points is zero. If you consider some day to day examples like mixing of hot water and cold water for taking bath, you must have noticed that the temperature of hot water decreases as its heat is absorbed by the cold water till the temperature becomes same. This leads to concept of thermal equilibrium.
Thermal equilibrium
During exchange of heat from point of higher temperature to point of lower temperature, temperature of hot object decreases and cold object increases and after some time both attains the constant temperature condition. i.e. this exchange of heat is continued till both of them attain the same temperature, this condition is called as thermal equilibrium.
Then the thermal equilibrium is the condition of two systems in thermal contact with each other and they do not transfer any heat amongst them.
e.g. ice added to glass of water gets melts and attains the same temperature after some time is nothing but the example of thermal equilibrium.
To explain the conditions of thermal equilibrium the law termed as Zeroth law is very useful. It is called Zeroth law as it was introduced after first and second law of thermodynamics.
Let’s understand the law in detail……………!
Consider the following thermodynamic systems P, Q and R as shown in the fig.1) below.
Now suppose that the systems P and Q are in thermal equilibrium, also systems P and Q in thermal equilibrium, and then we can say that the systems Q and R are also in thermal equilibrium.
Hence the Zeroth law of thermodynamics is stated as, “If two systems are each in thermal equilibrium with third system, they are also in thermal equilibrium with each other”.
Consider the following examples…..!
- When you go to doctor for complaining of fever, then he checks our body temperature using thermometer. The temperature of thermometer rises till our body and thermometer attains the thermal equilibrium.
- A cup of hot tea kept on table gets cools down, and attain the temperature which is same of room temperature. i.e. tea and room atmosphere are in thermal equilibrium.
Some important points to note…..!
- Temperature measuring science is known as ‘thermometry’.
- Temperature of system is measurable quantity and can be measured with thermometers in different scales like Celsius, Fahrenheit, and Kelvin etc.
Thermal Equilibrium and Zeroth Law:-
Let’s solve some MCQ’s..!
Q.1) The transfer of heat from point of higher temperature to lower temperature continues till the system attains condition of….
a) thermodynamics
b) thermometry
c) thermal equilibrium
d) all of above
Answer
c) thermal equilibrium
Q.2) Temperature of system is measurable quantity and can be measured with thermometers in scales ….
a) Celsius
b) Kelvin
c) Fahrenheit
d) all of above
Answer
d) all of above
Q.2) Temperature of system is measurable quantity and can be measured with thermometers in scales ….
a) Celsius
b) Kelvin
c) Fahrenheit
d) all of above
Answer
d) all of above
Q.3) “If two systems are each in thermal equilibrium with third system, they are also in thermal equilibrium with each other” is the statement of….
a) Zeroth law of thermodynamics
b) First law of thermodynamics
c) Second law of thermodynamics
d) None of these
Answer
a) Zeroth law of thermodynamics
Q.4) Which among the following is appropriate process to explain the condition of thermal equilibrium?
a) Adiabatic process
b) Isothermal process
c) Isochoric process
d) Isobaric process
Answer
b) Isothermal process
