1
JEE Main 2017 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
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 :
A
$$\ell $$2 Y$$\alpha $$ $$\Delta $$T
B
$$\ell $$A Y$$\alpha $$ $$\Delta $$T
C
A Y$$\alpha $$ $$\Delta $$T
D
$${{AY} \over {\alpha \,\Delta T}}$$
2
JEE Main 2017 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
An engine operates by taking n moles of an ideal gas through the cycle ABCDA shown in figure. The thermal efficiency of the engine is : (Take Cv = 1.5 R, where R is gas constant)

JEE Main 2017 (Online) 8th April Morning Slot Physics - Heat and Thermodynamics Question 377 English
A
0.24
B
0.15
C
0.32
D
0.08
3
JEE Main 2017 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
An ideal gas has molecules with 5 degrees of freedom. The ratio of specific heats at constant pressure (Cp ) and at constant volume (Cv) is :
A
6
B
$${7 \over 2}$$
C
$${5 \over 2}$$
D
$${7 \over 5}$$
4
JEE Main 2017 (Offline)
MCQ (Single Correct Answer)
+4
-1
Change Language
CP and Cv are specific heats at constant pressure and constant volume respectively. It is observed that
CP – Cv = a for hydrogen gas
CP – Cv = b for nitrogen gas
The correct relation between a and b is
A
a = 28 b
B
a = 1/14 b
C
a = b
D
a = 14 b
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