Practice problems on JEE Mains, JEE Mains 2021 Mar 18 Shift 2

Question 1

For an adiabatic expansion of an ideal gas, the fractional change in its pressure is equal to (where γ is the ratio of specific heats):

Accepted Answer

−γVdV​

Answer

−γdVV​

Answer

VdV​

Answer

−γ1​VdV​

Question 2

Which of the following statements are correct?(A) Electric monopoles do not exist whereas magnetic monopoles exist.(B) Magnetic field lines due to a solenoid at its ends and outside cannot be completely straight and confined.(C) Magnetic field lines are completely confined within a toroid.(D) Magnetic field lines inside a bar magnet are not parallel.(E) χ=−1 is the condition for a perfect diamagnetic material, where χ is magnetic susceptibility. Choose the correct answer from the options given below :

Accepted Answer

(C) and (E) only

Answer

(A) and (B) only

Answer

(B) and (C) only

Answer

(B) and (D) only

Question 3

The oxidation states of nitrogen in NO,NO2​, N2​O and NO3​3 are in the order of :

Accepted Answer

NO3−​>NO2​>NO>N2​O

Answer

N2​O>NO2​>NO>NO3​

Answer

NO>NO2​>N2​O>NO3−​

Answer

NO2​>NO3−​>NO>N2​O

Question 4

The speed of electrons in a scanning electron microscope is 1×107 ms−1 . If the protons having the same speed are used instead of electrons, then the resolving power of scanning proton microscope will be changed by a factor of :

Accepted Answer

1837

Answer

1837​

Answer

18371​

Answer

1837​1​

Question 5

In a triangle ABC , if ∣BC∣=8,∣CA∣=7,∣AB∣=10 , then the projection of the vector AB on AC is equal to :

Accepted Answer

1485​

Answer

16115​

Answer

425​

Answer

20127​

Question 6

The decay of a proton to neutron is :

Accepted Answer

possible only inside the nucleus

Answer

not possible but neutron to proton conversion is possible

Answer

always possible as it is associated only with β+ decay

Answer

not possible as proton mass is less than the neutron mass

Question 7

Given below are two statementsStatement I : Non-biodegradable wastes are generated by the thermal power plantsStatement II : Bio-degradable detergents leads to eutrophication.In the light of the above statement, choose most appropriate answer from the option given below:

Accepted Answer

Both statement I and statement II are true

Answer

Statement I is true but statement II is false

Answer

Both statement I and statement II are false

Answer

Statement I is true but statement II is true

Question 8

Consider a uniform wire of mass M and L. It is bent into a semicircle. Its moment of inertia about a line perpendicular to the plane of the wire passing through the center is :

Accepted Answer

π2ML2​

Answer

41​π2ML2​

Answer

52​π2ML2​

Answer

21​π2ML2​

Question 9

Deficiency of vitamin K causes :

Accepted Answer

Increase in blood clotting time

Answer

Increase in fragility of RBC's

Answer

Decrease in blood clotting time

Answer

Cheilosis

Question 10

Define a relation R over a class of n×n real matrices A and B as ∘ARB iff there exists a non-singular matrix P such that PAP−1=B′′ . Then which of the following is true?

Accepted Answer

R is an equivalence relation

Answer

R is symmetric, transitive but not reflexive

Answer

R is reflexive, transitive but not symmetric

Answer

R is reflexive, symmetric but not transitive

Question 11

An ideal gas in a cylinder is separated by a piston in such a way that the entropy of one part is S1​ and that of the other part is S2​ . Given that S1​>S2​ . If the piston is removed then the total entropy of the system will be:

Accepted Answer

S1​+S2​

Answer

S1​×S2​

Answer

S2​S1​​

Answer

S1​−S2​

Question 12

A plane electromagnetic wave propagating along y-direction can have the following pair of electric field (E) and magnetic field ( B ) components.

Accepted Answer

Ex​,Bz​ or Ez​,Bx​

Answer

Ey​,Bx​ or Ex​,By​

Answer

Ex​,By​ or Ey​,Bx​

Answer

Ey​,By​ or Ez​,Bz​

Question 13

The area bounded by the curve 4y2=x2(4−x)(x−2) is equal to:

Accepted Answer

23π​

Answer

83π​

Answer

16π​

Answer

8π​

Question 14

A hard substance melts at high temperature and is an insulator in both solid and in molten state. This solid is most likely to be a/an:

Accepted Answer

Covalent solid

Answer

Molecular solid

Answer

Metallic solid

Answer

lonic solid