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

~~Us~~

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/3*α*K (2) P/*α*K (3) 3*α* /PK (4) 3PK*α*

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 m

^{3 }increases from 17°C to 27°C due to sunshine. The atmospheric pressure in the room remains 1 x 10

^{5 }Pa. If N

_{i}and N

_{f}are the numbers of gas molecules in the room before and after heating, then (N

_{f}– N

_{i}) will be:

(1) -1.61 x 10^{23} (2) 1.38 x 10^{23} (3) 2.5 x 10^{25} (4) -2.5 x 10^{25}

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 (N_{f} – N_{i}) 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, (n_{f} – n_{i}), due to heating? What is the change in number of molecules, (N_{f} – N_{i}), 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.*