1
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

A Carnot engine $(\mathrm{E})$ is working between two temperatures 473 K and 273 K . In a new system two engines - engine $E_1$ works between 473 K to 373 K and engine $E_2$ works between 373 K to 273 K . If $\eta_{12}, \eta_1$ and $\eta_2$ are the efficiencies of the engines $E, E_1$ and $E_2$, respectively, then

A
$\eta_{12}=\eta_1 \eta_2$
B
$\eta_{12}=\eta_1+\eta_2$
C
$\eta_{12} \geq \eta_1+\eta_2$
D
$\eta_{12}<\eta_1+\eta_2$
2
JEE Main 2025 (Online) 28th January Morning Shift
Numerical
+4
-1
Change Language

Two iron solid discs of negligible thickness have radii $R_1$ and $R_2$ and moment of intertia $I_1$ and $I_2$, respectively. For $R_2=2 R_1$, the ratio of $I_1$ and $I_2$ would be $1 / x$, where $\mathrm{x}=$ _______ .

Your input ____
3
JEE Main 2025 (Online) 28th January Morning Shift
Numerical
+4
-1
Change Language

In a measurement, it is asked to find modulus of elasticity per unit torque applied on the system. The measured quantity has dimension of $\left[M^a L^b T^c\right]$. If $b=3$, the value of $c$ is _________.

Your input ____
4
JEE Main 2025 (Online) 28th January Morning Shift
Numerical
+4
-1
Change Language

The moment of inertia of a solid disc rotating along its diameter is 2.5 times higher than the moment of inertia of a ring rotating in similar way. The moment of inertia of a solid sphere which has same radius as the disc and rotating in similar way, is $n$ times higher than the moment of inertia of the given ring. Here, $\mathrm{n}=$ ________ Consider all the bodies have equal masses.

Your input ____
JEE Main Papers
2023
2021
EXAM MAP