NEET 2020 NEWS
NATIONAL LEVEL OFFLINE TEST
Thermodynamics is a branch of Physics which deals with processes involving heat, work and internal energy. The system is defined as the region of space or quantity of matter under investigation or study. Everything external to that system is called environment or surroundings.
Thermodynamics also deals with macroscopic behaviour instead of microscopic behaviour of this system and understanding of such topics is very important to solve questions from this section. Given below in the article are quick notes and important questions on these topics with tips and tricks to help you prepare for NEET 2020.
The process by which one or more parameters of the thermodynamic system undergo changes is called thermodynamic processes. It includes:
Question: “CT “, given below is the molar heat capacity. Find its value at constant temperature?
(B) 0 < CT < Cv
(C) Cv < CT < Cp
(D) CT =
First law of Thermodynamics states that if a quantity of heat is supplied to a system capable of doing work, then the quantity of heat absorbed by the system is equal to the sum of increase in the internal energy of the system, i.e,
dQ= dU+ dW
Application of first law of dynamics-
Question: Read the processes given below and identify which of these violate the First law of Thermodynamics?
(A) W > 0, Q < 0, and ?Eint > 0
(B) W > 0, Q < 0, and ?Eint < 0
(C) W < 0, Q > 0, and ?Eint < 0
(D) W > 0, Q > 0, and ?Eint < 0
It states that state of entropy of the entire universe is always increasing with time and the changes in the universe can never be negative.
Question: How much heat is delivered to a higher temperature reservoir, if a heat pump uses 300 J or work to remove 400 J of heat from the low temperature reservoir?
Carnot Engine is a theoretical concept which gives the estimate of the maximum possible efficiency that a heat engine during the conversion of heat into work can possess.
Efficiency of Carnot Engine: Efficiency η of an engine is defined as the ratio between useful heat (heat converted into work) to the total heat supplied to the engine.
η = W / Q1 = [Q1- Q2]/ Q1 = 1-[Q2/Q1] = 1- T2/T1
Given below are steps involved in Carnot’s cycle:
Question: If a Carnot engine having an efficiency of 40% takes in heat from a source maintained at a temperature of 500k, then, what will be the intake temperature from the same source, if the engine’s efficiency now is 60%?
Question: How much heat energy is extracted from a high temperature reservoir per cycle if efficiency is 33% and work output is 24J per cycle?
|System||Part of the universe under investigation.|
|Open System||A system which can exchange both energy and matter with its surroundings.|
|Closed System||A system which permits passage of energy but not mass, across its boundary.|
|Isolated system||A system which can neither exchange energy nor matter with its surrounding.|
|Surroundings||Part of the universe other than system, which can interact with it.|
|Boundary||Anything which separates system from surrounding.|
|State variables||The variables which are required to be defined in order to define state of any system i.e. pressure, volume, mass, temperature, surface area, etc.|
|State Functions||Property of system which depend only on the state of the system and not on the path. Example: Pressure, volume, temperature, internal energy, enthalpy, entropy etc.|
|Intensive properties||Properties of a system which do not depend on mass of the system i.e. Temperature, pressure, density, concentration,|
|Extensive properties||Properties of a system which depend on mass of the system i.e. Volume, energy, enthalpy, entropy etc.|
|Process||Path along which state of a system changes.|
Thermodynamics is a important and vast topic when it comes to NEET. It is important to give due attention to this topic. Not only this, there are many sub topics in Thermodynamics which also require a lot of time and attention. These are given below:
Question: In the figure given below, in which path between initial state “I” and final state “f”, the work done on gas is greatest?
(C ) – C
Question: A Carnot freezer takes heat from water at 0oC and rejects it at the the temperature of 27oC. Given: the latent heat of ice is 336×103 J kg−1. Find the energy consumed by the freezer if 5 kg of water at 0oC is converted into ice at 0oC by the freezer.
(A) 1.67 ×× 105 J
(B) 1.68 ×× 106 J
(C ) 1.51 ×× 105 J
(D) 1.71 ×× 107 J
Question: What is the efficiency of Carnot energy which discharges 3 J of heat into low temperature reservoir for every 2 J of work output.
Question: Find, for which of the given processes the would the entropy change be zero?
(D) Constant volume
(E) None of these
Solution: (C )
Question: 200 g water is heated from 40oC to 60oC. Find the change in its internal energy where heat of water = 4184 J/kg/K. (The small change in expansion of water can be ignored.)
(A) 8.4 kJ
(B) 4.2 kJ
(C )16.7 kJ
(D) 167.4 kJ
Solution: (C )
Some tips and tricks to solve the NEET paper are given below:
Understanding the concepts to solve thermodynamics and NEET paper is prerequisite since there will be no direct questions and each question will require a different application and approach. So, be clear and thorough with your concepts.
Taking practice test, mock tests or sectional tests is a main process to score good marks in any exam. Similar is the case with NEET exam. Solving these tests and questions will prepare you about the level of questions asked and will also help you in increasing efficiency and time management for the exam day.
Following a proper time table is very important. It helps you to give proper time to studies and other activities. Also remember, taking breaks in between is equally important.
Take time out and revise all the important topics so that they are on your tips on the exam day.
For Exam Day,
On the day of exam, start with attempting easy questions first and then move to moderate question and if time permits then only attempt difficult questions. Also, do not spend more time on one question. If you are unable to solve it, leave that question and move to the next one.
Stay calm and focussed and do not panic if you can’t solve one question. Breathe in, relax and solve next one, and come back to it later on, if you have time.
Read questions carefully twice and then look at the options before solving a question. Since the paper would be MCQ, many a times, the question can be solved through elimination process and does not require the complete solving and application procedure.
Since almost 30 days are left for NEET, most of the students would be done with their syllabus and would be doing revision only. But the trick here is that, your revision also needs to be planned. Given below are some things that you can do in next 30 days to prepare well for NEET: