JEE Main 2017 (Online) 8th April Morning Slot | Heat and Thermodynamics Question 417 | Physics

A compressive force, F is applied at the two ends of a long thin steel rod. It is heated, simultaneously, such that its temperature increases by $$\Delta $$T. The net change in its length is zero. Let $$\ell $$ be the length of the rod, A its area of cross-section,Y its Young’s modulus, and $$\alpha $$ its coefficient of linear expansion. Then, F is equal to :

$$\ell $$² Y$$\alpha $$ $$\Delta $$T

$$\ell $$A Y$$\alpha $$ $$\Delta $$T

A Y$$\alpha $$ $$\Delta $$T

$${{AY} \over {\alpha \,\Delta T}}$$

JEE Main 2017 (Online) 8th April Morning Slot

MCQ (Single Correct Answer)

-1

An ideal gas has molecules with 5 degrees of freedom. The ratio of specific heats at constant pressure (C_p ) and at constant volume (C_v) is :

$${7 \over 2}$$

$${5 \over 2}$$

$${7 \over 5}$$

JEE Main 2017 (Offline)

MCQ (Single Correct Answer)

-1

An external pressure P is applied on a cube at 0^oC so that it is equally compressed from all sides. K is the bulk modulus of the material of the cube and $$\alpha$$ 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:

$${P \over {3\alpha K}}$$

$${P \over {\alpha K}}$$

$${3 \alpha \over {P K}}$$

3PK$$\alpha$$

JEE Main 2017 (Offline)

MCQ (Single Correct Answer)

-1

The temperature of an open room of volume 30 m³ increases from 17^oC to 27^oC due to the sunshine. The atmospheric pressure in the room remains 1 $$ \times $$ 10⁵ Pa. If N_i and N_f are the number of molecules in the room before and after heating, then N_f – N_i will be :

- 1.61 $$ \times $$ 10²³

1.38 $$ \times $$ 10²³

2.5 $$ \times $$ 10²⁵

- 2.5 $$ \times $$ 10²⁵

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