JEE Main 2021 Question Paper (25-Feb-2021) (Shift 1)

Question 1

A diatomic gas, having $ C_{P} = \frac{7}{2} R $ and $ C_{V} = \frac{5}{2} R $, is heated at constant pressure. The ratio $ \mathrm{d}U : \mathrm{d}Q : \mathrm{d}W $

Accepted Answer

$5:7:2$

Answer

$3:5:2$

Answer

$5:7:3$

Answer

$3:7:2$

Question 2

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$. Assertion $A$: When a rod lying freely is heated, no thermal stress is developed in it. Reason $R$: On heating, the length of the rod increases. In the light of the above statements, choose the correct answer from the options given below:

Accepted Answer

Both $A$ and $R$ are true but $R$ is NOT the correct explanation of $A$

Answer

Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

Answer

$A$ is false but $R$ is true

Answer

$A$ is true but $R$ is false

Question 3

The current $\left(i\right)$ at time $t=0$ and $t=\infty$ respectively for the given circuit is:

Accepted Answer

$\frac{5E}{18}, \frac{10E}{33}$

Answer

$ \frac{5E}{18}, \frac{18E}{55} $

Answer

$ \frac{10E}{33}, \frac{5E}{18} $

Answer

$ \frac{18E}{55}, \frac{5E}{18} $

Question 4

A solid sphere of radius $R$ gravitationally attracts a particle placed at $3R$ from its centre with a force $F_{1}$. Now a spherical cavity of radius $\left(\frac{R}{2}\right)$ is made in the sphere (as shown in figure) and the force becomes $F_{2}$. The value of $F_{1} : F_{2}$ is:

Accepted Answer

$50:41$

Answer

$41:50$

Answer

$25:36$

Answer

$36 \div 25$

Question 5

Given below are two statements:Statement I : A speech signal of $ 2\quad \mathrm{kHz}$ is used to modulate a carrier signal of $ 1\quad \mathrm{MHz}$. The bandwidth requirement for the signal is $ 4\quad \mathrm{kHz}$.Statement II : The side band frequencies are $ 1002\quad \mathrm{kHz}$ and $ 998\quad \mathrm{kHz}$. In the light of the above statements, choose the correct answer from the options given below:

Accepted Answer

Both Statement I and Statement II are true

Answer

Statement I is false but Statement II is true

Answer

Statement I is true but Statement II is false

Answer

Both Statement I and Statement II are false