Practice Questions

Q19.An amplitude modulated waves is represented by expression vm = 5(1 + 0. 6 cos 6280t) sin(211 × 104t) V. The minimum and maximum amplitudes of the amplitudes modulated wave are, respectively: (1) 2 3 V, 5V (2) 52 V, 8V (3) 5V, 8V (4) 3V, 5V

Q19.The graph which depicts the results of Rutherford gold foil experiment with α -particles is: θ : Scattering angle Y : Number of scattered α -particles detected (Plots are schematic and not to scale) JEE Main 2020 (08 Jan Shift 1) JEE Main Previous Year Paper (1) (2) (3) (4)

Q19.A radioactive nucleus decays by two different processes. The half-life for the first process is 10 s and that for the second is 100 s. The effective half-life of the nucleus is close to: (1) 9 s (2) 6 s (3) 55 s (4) 12 s

Q19.When a diode is forward biased, it has a voltage drop of 0. 5 V . the safe limit of current through the diode is 10 mA . If a battery of emf 1. 5 V is used in the circuit, the value of minimum resistance to be connected in series with the diode so that the current does not exceed the safe limit is : (1) 300 Ω (2) 50 Ω (3) 100 Ω (4) 200 Ω

Q20.If a semiconductor photo diode can detect a photon with a maximum wavelength of 400 nm, then its band gap energy is: Planck's constant h = 6. 63 × 10−34 J. s Speed of light c = 3 × 108 m s−1 (1) 1. 1 eV (2) 2. 0 eV (3) 1. 5 eV (4) 3. 1 eV

Q20.If the screw on a screw-gauge is given six rotations, it moves by 3mm on the main scale. If there are 50 divisions on the circular scale the least count of the screw gauge is: (1) 0.001cm (2) 0.02m (3) 0.01cm (4) 0.001mm

Q20.In the given circuit, value of Y is: (1) 0 (2) toggles between 0 and 1 (3) will not execute (4) 1 JEE Main 2020 (08 Jan Shift 2) JEE Main Previous Year Paper

Q20.Boolean relation at the output stage- Y for the following circuit is: (1) − − (2) A + B A + B (3) A ∙B (4) − − A ∙ B

Q20.Which of the following gives a reversible operation? (1) (2) (3) (4)

Q20.With increasing biasing voltage of a photo diode, the photocurrent magnitude: (1) remains constant (2) increases initially and after attaining certain value, it decreases (3) increases linearly (4) increases initially and saturates finally

Q20.Identify the operation performed by the circuit given below : (1) NAND (2) OR (3) AND (4) NOT

Q20.Using screw gauge of pitch 0. 1 cm and 50 divisions on its circular scale, the thickness of an object is measured. It should correctly be recorded as, (1) 2. 121 cm (2) 2. 124 cm (3) 2. 125 cm (4) 2. 123 cm

Q20.In the following, digital circuit, what will be the output a ' Z', when the input (A, B) are (1, 0), (0, 0), (1, 1), (0, 1) (1) 0, 0, 1, 0 (2) 1, 0, 1, 1 (3) 1, 1, 0, 1 (4) 0, 1, 0, 0

Q21.The speed verses time graph for a particle is shown in the figure. The distance travelled (in m) by the particle during the time interval t = 0 to t = 5 s will be __________

Q21.The centre of mass of a solid hemisphere of radius 8 cm is x cm from the centre of the flat surface. Then value of x is

Q23.Nitrogen gas is at 300 °C temperature. The temperature (in K ) at which the rms speed of a H2 molecule would be equal to the rms speed of a nitrogen molecule, is … … … . (Molar mass of N2 gas 28 g ).

Q24.A galvanometer coil has 500 turns and each turn has an average area of 3 × 10−4m2 . If a torque of 1. 5 Nm is required to keep this coil parallel to a magnetic field when a current of 0. 5A is flowing through it, the strength of the field (in T) is _________ .

Q24.In a Young's double slit experiment 15 fringes are observed on a small portion of the screen when light of wavelength 500 nm is used. Ten fringes are observed on the same section of the screen when another light source of wavelength λ is used. Then the value of λ is (in nm ) __________.

Q24.A prism of angle A = 1° μ = 1. 5 . A good estimate for the minimum angle of deviation (in degrees) is close to N . Value of N is … … … 10

Q24.In a fluorescent lamp choke (a small transformer) 100V of reverse voltage is produced when the choke current changes uniformly from 0.25A to 0 in a duration of 0.025ms . The self-inductance of the choke (in mH ) is estimated to be ________

Q25.A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is 30 cm and the refractive index of the lens material is 1.5, then the focal length of the lens (in cm) is ___________. 1 − (I) to n2

Q26.The de Broglie wavelength of an electron in the 4th Bohr orbit is: (1) 2πa0 (2) 4πa0 (3) 6πa0 (4) 8πa0

Q26.The difference between the radii of 3rd and 4th orbits of L2+i is ΔR1 . The difference between the radii of 3rd and 4th orbits of He+ ΔR2. Ratio ΔR1 : ΔR2 is : (1) 8 : 3 (2) 3 : 8 (3) 2 : 3 (4) 3 : 2

Q26.The region in the electromagnetic spectrum where the Balmer series lines appear is: (1) Visible (2) Microwave (3) Infrared (4) Ultraviolet

Q28.The true statement amongst the following is: (1) Both ΔS and S are functions of temperature. (2) Both S and ΔS are not functions of temperature (3) S is not a function of temperature but ΔS is a function of temperature (4) S is a function of temperature but ΔS is not a function of temperature