दोस्तों यहां पर **JEE Main 2021 20th July Shift 1 Physics** का Solved Paper दिया गया है तथा आपको JEE Main का **ऑनलाइन टेस्ट **भी इस वेबसाइट पर दिया गया है।

Section A |

**1. The radiation corresponding to 3 → 2 transition of a hydrogen atom falls on a gold surface to generate photoelectrons. These electrons are passed through a magnetic field of 5 x 10 ^{–}⁴ T. Assume that the radius of the largest circular path followed by these electrons is 7 mm, the work function of the metal is : (Mass of electron = 9.1 x 10^{–}³¹ kg)**

(1) 0.82 eV

(2) 0.16 eV

(3) 1.88 eV

(4) 1.36 eV

**2. If ^{} and ^{} are two vectors satisfying the relation ^{.} = [^{ }x ^{}]. Then the value of [^{ }– ^{}] will be :**

**3. The value of current in the 6Ω resistance is :**

(1) 4 A

(2) 6 A

(3) 8 A

(4) 10 A

**4. A deuteron and an alpha particle having equal kinetic energy enter perpendicular into a magnetic field. Let r _{d} and r_{α} be their respective radii of circular path. The value of ta is r_{d}/r_{α} equal to**

(1) √2

(2) 1

(3) 2

(4) 1/√2

**5. A radioactive material decays by simultaneous emissions of two particles with half lives of 1400 years and 700 years respectively. What will be the time after which one-third of the material remains ? (Take In3 = 1.1)**

(1) 1110 years

(2) 340 years

(3) 740 years

(4) 700 years

**6. A person whose mass is 100 kg travels from Earth to Mars in a spaceship. Neglect all other objects in sky and take acceleration due to gravity on the surface of the Earth and Mars as 10 m/s² and 4 m/s² respectively. Identify from the below figures, the curve that fits best for the weight of the passenger as a function of time.
**(1) b

(2) a

(3) x

(4) d

**7. The amount of heat needed to raise the temperature of 4 moles of a rigid diatomic gas from 0°C to 50°C when no work is done is…….. (R is the universal gas constant)**

(1) 750 R

(2) 175 R

(3) 500 R

(4) 250 R

**8. The value of tension in a long thin metal wire has been changed from T₁ to T₂. The lengths of the metal wire at two different values of tension T₁ and T₂ are l₁ and l₂ respectively. The actual length of the metal wire is :**

**9. A butterfly is flying with a velocity 4√2 m/s in North-East direction. Wind is slowly blowing at 1 m/s from North to South. The resultant displacement of the butterfly in 3 seconds is :**

(1) 15 m

(2) 12 √2 m

(3) 3 m

(4) 20 m

**10. A certain charge Q is divided into two parts qand (Q-q). How should the charges Q and q be divided so that q and (Q-q) placed at a certain distance apart experience maximum electrostatic repulsion?**

(1) Q = q/2

(2) Q = 3q

(3) Q = 2q

(4) Q = 4q

**11. The entropy of any system is given by
Where α and β are the constants μ J, k and R are no. of moles, mechanical equivalent of heat, Boltzmann constant and gas constant respectively. (take S = dQ/T]
Choose the incorrect option from the following:**

(1) S, β,k and μR have the same dimensions.

(2) α and J have the same dimensions.

(3) S and α have different dimensions.

(4) α and k have the same dimensions.

**12. The arm PQ of a rectangular conductor is moving from x = 0 to x = 2b outwards and then inwards from x = 2b to x = 0 as shown in the figure. A uniform magnetic field perpendicular to the plane is acting from x = 0 to x = b. Identify the graph showing the variation of different quantities with distance.
**

(1) A-Flux, B-EMF, C-Power dissipated

(2) A-Power dissipated, B-Flux, C-EMF

(3) A-Flux, B-Power, dissipated, C-EMF

(4) A-EMF, B-Power dissipated, C-Flux

**13. A steel block of 10 kg rests on a horizontal floor as shown. When three iron cylinders are placed on it as shown, the block and cylinders go down with an acceleration 0.2 m/s². The normal reaction R’ by the floor if mass of the iron cylinders are equal and of 20 kg each, is_______
(take g = 10 m/s² and μ = 0.2]
**(1) 714

(2) 716

(3) 684

(4) 686

**14. For the circuit shown below, calculate the value of I _{z} :
**

(1) 0.15 A

(2) 0.05 A

(3) 0.1 A

(4) 25m A

**15. A nucleus of mass M emits γ-ray photon of frequency’v’. The loss of internal energy by the nucleus is :**

(1) 0

(2)

(3) hv

(4)

**16. Region I and II are separated by a spherical surface of radius 25 cm. An object is kept in region I at a distance of 40 cm from the surface. The distance of the image from the surface is
**(1) 55.44 cm

(2) 9.52 cm

(3) 37.58 cm

(4) 18.23 cm

**17. AC voltage V(t) = 20 sinot of frequency 50 Hz is applied to a parallel plate capacitor. The separation between the plates is 2 mm and the area is 1 m². The amplitude of the oscillating displacement current for the applied AC voltage is________
[take ε _{₀} = 8.85 x 10^{–}¹² F/m]**

(1) 21.14 ua

(2) 83.37 ua

(3) 55.58 uA

(4) 27.79 uA

**18. The normal reaction ‘N’ for a vehicle of 800 kg mass, negotiating a turn on a 30° banked road at maximum possible speed without skidding is_______ x10³ kg m/s²
[Given cos30o = 0.87, μs = 0.2]**

(1) 12.4

(2) 7.2

(3) 6.96

(4) 10.2

**19. A current of 5A is passing through a non-linear magnesium wire of cross-section 0.04m². At every point, the direction of current density is at an angle of 60° with the unit vector of area of cross-section. The magnitude of electric field at every point of the conductor is :
Resistivity of magnesium = 44 x 10 ^{–}⁸2Ωm**

(1) 11 x 10^{–}³ V/m

(2) 11 x 10^{–}⁵ V/m

(3) 11x 10^{–}⁷ V/m

(4) 11 x 10^{–}² V/m

**20. Consider a mixture of gas molecule of types A, B and C having masses m _{A} < m_{B} < m_{C} ratio of their root mean square speeds at normal temperature and pressure is :**

Section B |

**21. A body having specific charge 8 μC/g is resting on a frictionless plane at a distance 10 cm from the wall (as shown in the figure). It starts moving towards the wall when uniform electric field of 100 V/m is applied horizontally toward the wall. If the collision of the body with the wall is perfectly elastic. then the time period of the motion will be______ s.**

**22. In a spring gun having spring constant 100 N/m a small ball ‘B’ of mass 100 g is put in its barrel (as shown in figure) by compressing the spring through 0.05 m. There should be a box placed at a distance ď on the ground so that the ball falls in it. If the ball leaves the gun horizontally at a height of 2 m above the ground. The value of d is____ m.
(g = 10 m/s²).**

**23. A rod of mass M and length L is lying on a horizontal frictionless surface. A particle of mass ‘m’ travelling along the surface hits at one end of the rod with velocity ‘u’ in a direction perpendicular to the rod. The collision is completely elastic. After collision, particle comes to rest. The ratio of masses
(m/M) is 1/x . the value of ‘x’ will be ………**

**24. An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification ‘6’, gives an unresolved image. A resolved image is observed at infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0.6 m, if the focal length of the eyepiece is
equal to______ cm.**

**25. In an LCR series circuit, an inductor 30 mH and a resistor 1 Ω are connected to an AC source of angular frequency 300 rad/s. The value of capacitance for which, the current leads the voltage by 45° is 1/x x 10^{–}³ F. Then the value of x is_______**

**26. The frequency of a car horn encountered a change from 400 Hz to 500 Hz, when the car approaches a vertical wall. If the speed of sound is 330 m/s. Then the speed of car is ______ km/h.**

**27. A carrier wave Vc(t) = 160 sin(2π x 10⁶t) volts is made to vary between V _{max} = 200 V and V_{min} = 120 V by a message signal V_{m}(t) = A_{m} sin(2π x 10³t) volts. The peak voltage Am of the modulating signal is______**

**28. A circular disc reaches from top to bottom of an inclined plane of length ‘L’. When it slips down the plane, it takes time’t₁’.when it rolls down the plane, it takes time t₂. The value of . The value of x will be_____**

**29. The amplitude of wave disturbance propagating in the positive x-direction is given by at time t = 0 and at t = 1s, where x and y are in metres. The shape of wave does not change during the propagation. The velocity of the wave will be_____ m/s.**

**30. In the reported figure, heat energy absorbed by a system in going through a cyclic process is_____πJ.
**

## JEE Main Solved Paper Question Answer With Solutions

### JEE Main 2021 Paper with Solutions

⚫ |
JEE Main 2021 Paper with Solutions – 20^{th} July – Shift 1 |

1. |
JEE Main Physics Question Paper |

2. |
JEE Main Chemistry Question Paper |

3. |
JEE Main Maths Question Paper |