SOLVE JEE (MAIN) 2017 WITH A SMILE – IV

Let Us YOU Solve Physics JEE (MAIN) 2017 Physics Paper

We shall guide you to solve few more Physics questions from JEE (Main) 2017, Paper-1. All students at + 2 level, who wish to pursue B.E. /B. Tech courses in Indian Engineering Institutes, must secure good ranks in JEE (Main). So it’s a good idea you learnt to connect the questions to the relevant theories, study them with absolute clarity from the video lectures  @ PhysicsAcademyOnline.com, and apply them to solve the questions. This way, if a close contact is purposefully maintained between questions and theories, the study of Physics becomes enjoyable and stress-free. Needless to say, more practice leads you to more lectures at both basic and advanced levels. In turn they make you more self-reliant and fighting fit for the Competitive Exams ahead. And you can always check your own solution against our video solution given at the end of every question.

Question 09:  An external pressure P is applied to a cube at 0°C, so that it is equally compressed from all sides. K is the bulk modulus of the material of the cube and  α  is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by:

(1) P/3αK                 (2) P/αK                  (3) 3α /PK                    (4) 3PKα

Of the various options, which has/have the same dimension as temperature? subscribe to PhysicsAcademyOnline.com, and learn the technique here:  Chapter Name – Mechanics; Category –  Basic; Topic Name – Physical Quantities and Their Measurement; Video Name – Uses of Dimensional Analysis.

Still, you have to choose between two options. What is the relation between the coefficients of volume and linear expansion? Discussed here:  Chapter Name – Heat and Thermodynamics; Category –  Basic; Topic Name – Thermal Expansion; Video Name – Thermal Expansion of Solids.

Now, you can easily guess the correct option. That was a shortcut. Another method is discussed below.

What is the change in volume of the cube under pressure? Formula here:  Chapter Name – Elasticity and Fluid Mechanics; Category –  Basic; Topic Name – Elasticity; Video Name – Bulk Modulus & Relations among Elastic Constants.

What is the required change in volume of the cube by heating? How do you express it in terms of coefficient of linear expansion, a , and temperature rise? Discussed in the same lecture titled “Thermal Expansion of Solids”.

You are close to the answer.

Question 11:  The temperature of an open room of volume 30 mincreases from 17°C to 27°C due to sunshine. The atmospheric pressure in the room remains 1 x 10Pa. If Ni and Nf are the numbers of gas molecules in the room before and after heating, then (Nf – Ni) will be:

(1) -1.61 x 1023           (2) 1.38 x 1023            (3) 2.5 x 1025           (4) -2.5 x 1025

What is the number of moles, n, present in a given volume of a gas at given temperature and pressure? Can be found here:    Chapter Name – Heat and Thermodynamics; Category –  Basic; Topic Name – Thermal Expansion; Video Name – Expansion of Gases II.

You can already predict whether (Nf – Ni) is positive or negative. But although that narrows your search, you still require to calculate its numerical value. What is the change in number of moles, (nf – ni), due to heating? What is the change in number of molecules, (Nf – Ni), due to heating? It’s convenient to write in symbols first, and put data in the last step.

Interested readers are welcome to see similar problems in:  Chapter Name – Heat and Thermodynamics; Category –  Basic; Topic Name – Thermal Expansion; Video Name – Problems on Expansion of Gases.