Practice Questions

Q20.For a certain radioactive process, the graph between ln R and t(sec) is obtained as shown in the figure. Then the value of half life for the unknown radioactive material is approximately: (1) 9. 15 sec (2) 6. 93 sec (3) 2. 62 sec (4) 4. 62 sec

Q20.Given below are two statements: Statement I : p −n junction diodes can be used to function as a transistor, simply by connecting two diodes, back to back, which acts as the base terminal Statement II: In the study of transistors, the amplification factor β indicates ratio of the collector current to the base current. In the light of the above statements, choose the correct answer from the options given below. (1) Both Statement I and Statement II are false (2) Statement I is true but Statement II is false (3) Statement I is false but Statement II is true (4) Both Statement I and Statement II are true

Q20. Assertion A : If in five complete rotations of the circular scale, the distance travelled on the main scale of the screw gauge is 5 mm and there are 50 total divisions on a circular scale, then the least count is 0. 001 cm. Reason R : Least Count = Total divisionsPitchon circular scale In the light of the above statements, choose the most appropriate answer from the options given below. (1) A is not correct but R is correct. (2) Both A and R are correct and R is the correct explanation of A. (3) A is correct but R is not correct. (4) Both A and R are correct and R is NOT the correct explanation of A.

Q20.If an emitter current is changed by 4 mA, the collector current changes by 3 . 5 mA. The value of 𝛽 will be: (1) 3.5 (2) 0.5 (3) 0.875 (4) 7

Q20.The pitch of the screw gauge is 1 mm and there are 100 divisions on the circular scale. When nothing is put in between the jaws, the zero of the circular scale lies 8 divisions below the reference line. When a wire is placed between the jaws, the first linear scale division is clearly visible while 72nd division on circular scale coincides with the reference line. The radius of the wire is (1) 1. 64 mm (2) 0. 82 mm (3) 0. 90 mm (4) 1. 80 mm

Q20.Statement I : To get a steady DC output from the pulsating voltage received from a full wave rectifier we can connect a capacitor across the output parallel to the load 𝑅𝐿. Statement II : To get a steady DC output from the pulsating voltage received from a full wave rectifier we can connect an inductor in series with 𝑅𝐿. In the light of the above statements, choose the most appropriate answer from the options given below : (1) Both Statement I and Statement II are false (2) Both Statement I and Statement II are true (3) Statement I is false but Statement II is true (4) Statement I is true but Statement II is false

Q20.Match List –I with List – II. List –I List – II (a) 10 km height over earth's surface (i) Thermosphere (b) 70 km height over earth's surface (ii) Mesosphere (c) 180 km height over earth's surface (iii) Stratosphere (d) 270 km height over earth's surface (iv) Troposphere (1) (a )-( iv ), ( b )-( iii ), ( c )-( ii ), ( d )-( i) (2) (a )-( i ), ( b )-( iv ), ( c )-( iii ), ( d )-( ii) (3) (a )-( iii ), ( b )-( ii ), ( c )-( i ), ( d )-( iv) (4) (a )-( ii ), ( b )-( i ), ( c )-( iv ), ( d )-( iii)

Q20.In the given figure, each diode has a forward bias resistance of 30 Ω and infinite resistance in reverse bias. The current 𝐼1 will be : (1) 2 . 0 A (2) 3 . 75 A (3) 2 . 73 A (4) 2 . 35 A

Q20.A carrier signal C(t) = 25 sin(2. 512 × 1010t) is amplitude modulated by a message signal m(t) = 5 sin(1. 57 × 108t) and transmitted through an antenna. What will be the bandwidth of the modulated signal ? (1) 8 GHz (2) 2. 01 GHz (3) 1987. 5 MHz (4) 50 MHz

Q20.An antenna is mounted on a 400 m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44 km ? (1) 605 m (2) 302 m (3) 37. 8 m (4) 75. 6 m JEE Main 2021 (27 Aug Shift 2) JEE Main Previous Year Paper

Q20.The vernier scale used for measurement has a positive zero error of 0. 2 mm. If while taking a measurement it was noted that 0 on the vernier scale lies between 8. 5 cm and 8. 6 cm. Vernier coincidence is 6, then the correct value of measurement is cm. (least count = 0. 01 cm ) (1) 8. 36 cm (2) 8. 54 cm (3) 8. 58 cm (4) 8. 56 cm

Q20.When radiation of wavelength λ is incident on a metallic surface, the stopping potential of ejected photoelectrons is 4. 8 V . If the same surface is illuminated by radiation of double the previous wavelength, then the stopping potential becomes 1. 6 V . The threshold wavelength of the metal is: (1) 2λ (2) 4λ (3) 8λ (4) 6λ + N acts on a particle. The work done by this force when the particle is moved from

Q20.For the circuit shown below, calculate the value of Iz : JEE Main 2021 (20 Jul Shift 1) JEE Main Previous Year Paper (1) 25 mA (2) 0. 15 A (3) 0. 1 A (4) 0. 05 A

Q20.In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are 50 divisions on the circular scale, and the main scale moves by 0. 5 mm on a complete rotation. For a particular observation the reading on the main scale is 5 mm and the 20th division of the circular scale coincides with reference line. Calculate the true reading. (1) 5. 20 mm (2) 5. 00 mm (3) 5. 15 mm (4) 5. 25 mm

Q20.Draw the output signal Y in the given combination of gates. JEE Main 2021 (26 Feb Shift 2) JEE Main Previous Year Paper (1) (2) (3) (4)

Q20.Two identical antennas mounted on identical towers are separated from each other by a distance of 45 km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight ? (Assume radius of earth is 6400 km) (1) 19. 77 m (2) 39. 55 m (3) 79. 1 m (4) 158. 2 m

Q21.In the reported figure of earth, the value of acceleration due to gravity is same at point A and C but it is smaller than that of its value at point B (surface of the earth). The value of OA : AB will be x : 5 . The value of x is Q22. 1 mole of rigid diatomic gas performs a work of Q5 when heat Q is supplied to it. The molar heat capacity of the gas during this transformation is xR 8 . The value of x is [ R universal gas constant]

Q21.The radius of a sphere is measured to be (7. 50 ± 0. 85) cm. Suppose the percentage error in its volume is x. The value of x, to the nearest x, is ___ .

Q21.Three particles P, Q and R are moving along the vectors A = ˆi +ˆj, B = ˆj + ˆk and C = −ˆi +ˆj, respectively. They strike on a point and start to move in different directions. Now particle P is moving normal to the plane → → → which contains vector A and B. Similarly particle Q is moving normal to the plane which contains vector A → and C. The angle between the direction of motion of P and Q is cos−1( √x1 ). Then the value of x is .

Q21.A swimmer wants to cross a river from point A to point B. Line AB makes an angle of 30° with the flow of the river. The magnitude of the velocity of the swimmer is the same as that of the river. The angle θ with the line AB should be _______ °, so that the swimmer reaches point B. JEE Main 2021 (27 Jul Shift 2) JEE Main Previous Year Paper

Q21.A force of F = (5y 20)ˆj y = 0 m to y = 10 m is ________ J .

Q21.Two spherical balls having equal masses with radius of 5 cm each are thrown upwards along the same vertical direction at an interval of 3 s with the same initial velocity of 35 m s−1 , then these balls collide at a height of _____ m , (take g = 10 m s−2 )

Q21.Suppose two planets (spherical in shape) of radii R and 2R, but mass M and 9M respectively have a centre to centre separation 8R as shown in the figure. A satellite of mass m is projected from the surface of the planet of mass M directly towards the centre of the second planet. The minimum speed v required for the satellite to GM reach the surface of the second planet is , then the value of a is R √a7 [Given : The two planets are fixed in their position]

Q21.A body of mass 2 kg moving with a speed of 4 m s-1 makes an elastic collision with another body at rest and continues to move in the original direction but with one fourth of its initial speed. The speed of the two body centre of mass is $x/10$. Find the value of x.

Q21.A car is moving on a plane inclined at 30° to the horizontal with an acceleration of 10 m s−2 parallel to the plane upward. A bob is suspended by a string from the roof of the car. The angle in degrees which the string makes with the vertical is (Take g = 10 m s−2 )