JEE Exam  >  JEE Tests  >  Additional Study Material for JEE  >  JEE Main 2020 Question Paper with Solution (7th January - Evening) - JEE MCQ

JEE Main 2020 Question Paper with Solution (7th January - Evening) - JEE MCQ


Test Description

30 Questions MCQ Test Additional Study Material for JEE - JEE Main 2020 Question Paper with Solution (7th January - Evening)

JEE Main 2020 Question Paper with Solution (7th January - Evening) for JEE 2024 is part of Additional Study Material for JEE preparation. The JEE Main 2020 Question Paper with Solution (7th January - Evening) questions and answers have been prepared according to the JEE exam syllabus.The JEE Main 2020 Question Paper with Solution (7th January - Evening) MCQs are made for JEE 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for JEE Main 2020 Question Paper with Solution (7th January - Evening) below.
Solutions of JEE Main 2020 Question Paper with Solution (7th January - Evening) questions in English are available as part of our Additional Study Material for JEE for JEE & JEE Main 2020 Question Paper with Solution (7th January - Evening) solutions in Hindi for Additional Study Material for JEE course. Download more important topics, notes, lectures and mock test series for JEE Exam by signing up for free. Attempt JEE Main 2020 Question Paper with Solution (7th January - Evening) | 72 questions in 180 minutes | Mock test for JEE preparation | Free important questions MCQ to study Additional Study Material for JEE for JEE Exam | Download free PDF with solutions
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 1

If weight of an object at pole is 196 N then weight at equator is [g = 10 m/s2 ; radius of earth = 6400 Km]

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 1

at pole, weight = mg = 196
m = 19.6 kg
at equator, weight = mg – mω2R

= 195.33 N

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 2

​In a house 15 Bulbs of 45 W, 15 bulbs of 100 W, 15 bulbs of 10 W and Two heaters of 1 KW each is connected to 220 V Mains supply then find minimum fuse current 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 2

Total power is (15 × 45) + (15 × 100) + (15 × 10) + (2 × 1000)
= 4325 W
So current is = 4325/220
= 19.66 A
Ans is 20 Amp.

1 Crore+ students have signed up on EduRev. Have you? Download the App
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 3

In an adiabatic process, volume is doubled then find the ratio of final average relaxation time & initial relaxation time. Given 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 3

relaxation time 
and 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 4

A block of mass 10kg is suspended from string of length 4m. When pulled by a force F along horizontal from midpoint. Upper half of string makes 45° with vertical, value of F is

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 4


JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 5

The surface mass density of a disc of radius a varies with radial distance as σ = A + Br where A & B are positive constants then moment of inertia of the disc about an axis passing through its centre and perpendicular to the plane  

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 5


σ = A + Br

I = 
(A + Br )2πr3 dr

= 2pa4 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 6

Cascaded Carnot engine is an arrangement in which heat sink of one engine is source for other. If high temperature for one engine is T1, low temperature for other engine is T2 (Assume work done by both engine is same) Calculate lower temperature of first engine.

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 6

Let, QH : Heat input to Ist engine
       QL : Heat rejected from Ist
       engine
       QL': Heat rejected f rom IInd             engine
Work done by Ist engine = work done by IInd engine
QH – QL = QL – QL'
2QL = QH + QL'

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 7

Activity of a substance changes from 700 s–1 to 500 s–1 in 30 minute. Find its half-life in minutes

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 7


=> ln2 = λt1/2...........(i)

(i)/(ii)

(2.06004) 30 = t1/2 = 61.8 min.

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 8

In YDSE, separation between slits is 0.15 mm, distance between slits and screen is 1.5 m and wavelength of light is 589 nm, then fringe width is  

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 8


= 5.9mm

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 9

An ideal fluid is flowing in a pipe in streamline flow. Pipe has maximum and minimum diameter of 6.4 cm and 4.8 cm respectively. Find out the ratio of minimum to maximum velocity.

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 9

Using equation of continuity
A1V1 = A2V2

 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 10

There is a electric circuit as shown in the figure. Find potential difference between points a and b.

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 10

Diode is in forward bias, so it will behave as simple wire so,


So Vab= 10V

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 11

A particle of mass m and positive charge q is projected with a speed of v0 in y–direction in the presence of electric and magnetic field are in x–direction. Find the instant of time at which the speed of particle becomes double the initial speed. 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 11


As(magnitude of velocity does not change in y–z plane)

∴ 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 12

Two sources of sound moving with same speed v and emitting frequency of 1400 Hz are moving such that one source s1 is moving towards the observer and s2 is moving away from observer. If observer hears beat frequency of 2 Hz. Then find the speed of source. Given
Vsound >> VSource
Vsound = 350 m/s 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 12

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 13

An electron & a photon have same energy E. Find the ratio of de Broglie wavelength of electron to wavelength of photon. Given mass of electron is m & speed of light is C.

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 13

λd for electron = 
λ for photon = hC/E
Ratio =  

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 14

​A ring is rotated about diametric axis in a uniform magnetic field perpendicular to the plane of the ring. If initially the plane of the ring is perpendicular to the magnetic field. Find the instant of time at which EMF will be maximum & minimum respectively :

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 14


When ωt = π
∵  φ will have maximum.
∵ e will be minimum.
t =  = 5 sec.

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 15

Electric field in space is given by A positively charged particle at (0, 0, π/K) is given velocity v0kˆ at t = 0. Direction of f orce acting on particle is 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 15

Force due to electric field is in direction 
because at t = 0, E = 
Force due to magnetic field is in direction 
∴ it is parallel to
∴ net force is antiparallel to 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 16

Focal length of convex lens in air is 16 cm (μglass = 1.5). Now the lens is submerged in liquid of refractive index 1.42. Find the ratio of focal length in medium to focal length in air has closest value

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 16



JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 17

A lift of mass 920 kg has a capacity of 10 persons. If average mass of person is 68 kg. Friction f orce between lift and lift shaft is 6000 N. The minimum power of motor required to move the lift upward with constant velocity 3 m/s is [g = 10 m/s2]

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 17

Net force on motor will be
Fm = [920 + 68(10)]g + 6000
      = 22000 N
So, required power for motor

= 22000 x 3
= 66000 watt 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 18

The hysteresis curve for a material is shown in the figure. Then for the material retentivity, coercivity and saturation magnetization respectively will be

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 18


x = retentivity
y = coercivity
z = saturation magnetization

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 19

​An inductor of inductance 10 mH and a resistance of 5Ω is connected to a battery of 20 V at t = 0. Find the ratio of current in circuit at t = ∞ to current at t = 40 sec.

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 19




JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 20

Find the dimension of 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 20

Energy density in magnetic field = 

*Answer can only contain numeric values
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 21

A capacitor of 60 pF charged to 20 volt. Now battery is removed and then this capacitor is connected to another identical uncharged capacitor. Find heat loss in nJ.


Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 21



V0 = 20 V
Heat loss = Ui – Uf



= 6 × 10–9 J = 6 nJ

*Answer can only contain numeric values
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 22

When m gram of steam at 100°C is mixed with 200 gm of ice at 0°C. it results in water at 40°C. Find the value of m in gram .
(given : Latent heat of fusion (Lf) = 80 cal/gm,  Latent heat of vaporisation (Lv) = 540 cal/gm., specific heat of water (Cw)= 1 cal/gm/°C)


Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 22

*Answer can only contain numeric values
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 23

A solid cube of side 'a' is shown in the figure. Find maximum value of for which the block does 
not topple before sliding.


Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 23

For no toppling

For no toppling



0.2a + 0.4b ≤ 0.5a
0.4b ≤ 0.3a

b ≤ 0.75a (in limiting case)
But it is not possible as b can maximum be equal to 0.5a 
∴ 

*Answer can only contain numeric values
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 24

Magnitude of resultant of two vectors is equal to magnitude of .  Find the angle between 
and resultant of 2and 


Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 24


So angle between (2 + ) and is 90°
Alternate solution

P2 + Q2 + 2PQcosθ = P2
Q + 2Pcosθ =θ
cosθ =

tan α =  = ∞
∵ [2Pcosθ + Q = 0]
α = 90°

*Answer can only contain numeric values
JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 25

A battery of unknown emf connected to a potentiometer has balancing length 560 cm. If a resistor of resistance 10W is connected in parallel with the cell the balancing length change by 60 cm. If the internal resistance of the cell is n/10 Ω, the value of 'n' is 


Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 25

Let the emf of cell is e internal resistance is 'r' and potential gradient is x.
only cell connected :
ε = 560 x ................. (i)
After connecting the resistor
................... (ii)
from (1) and (2)

56 = 50 + 5r

n = 12

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 26

Which of the following reactions are possible?
(A)
 
(B)

(C)

(D)

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 26

Vinyl halides and aryl halides do not give Friedel craft's reaction.

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 27

A and B are in the given reaction ?

 

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 27

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 28

The correct statement about gluconic acid is

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 28

Gluconic acid 
is obtained by partial oxidation of glucose by Tollen's reagent or Fehling solution or Br2,H2O.
Gluconic acid can not form hemiacetal or acetal
 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 29

Stability order of following alkoxide ions is

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 29

When negative charge is delocalised with electron withdrawing group like (NO2) then stability increases.
(A) Negative charge is delocalised with NO2 group
(B) Negative charge is delocalised with carbon of alkene
(C) Negative charge is localised 

JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 30


A and B are –

Detailed Solution for JEE Main 2020 Question Paper with Solution (7th January - Evening) - Question 30

View more questions
22 videos|162 docs|17 tests
Information about JEE Main 2020 Question Paper with Solution (7th January - Evening) Page
In this test you can find the Exam questions for JEE Main 2020 Question Paper with Solution (7th January - Evening) solved & explained in the simplest way possible. Besides giving Questions and answers for JEE Main 2020 Question Paper with Solution (7th January - Evening), EduRev gives you an ample number of Online tests for practice

Top Courses for JEE

22 videos|162 docs|17 tests
Download as PDF

Top Courses for JEE