Practice Questions

Q20.A transmitting antenna at top of a tower has a height of 50 m, and the height of receiving antenna is, 80 m. What is the range of communication for the line of sight (LOS) mode? [use radius of the earth = 6400 km] JEE Main 2021 (26 Aug Shift 2) JEE Main Previous Year Paper (1) 80. 2 km (2) 144. 1 km (3) 57. 28 km (4) 45. 5 km

Q20.In the following logic circuit the sequence of the inputs A, B are (0, 0), (0, 1), (1, 0) and (1, 1). The output Y for this sequence will be : (1) 0, 1, 0, 1 (2) 0, 0, 1, 1 (3) 1, 1, 1, 0 (4) 1, 0, 1, 0

Q20.For a transistor in CE mode to be used as an amplifier, it must be operated in: (1) Cut-off region only (2) Saturation region only (3) The active region only (4) Both cut-off and Saturation

Q20.Find the truth table for the function Y of A and B represented in the following figure. (1) A B Y (2) A B Y 0 0 0 0 0 1 0 1 1 0 1 0 1 0 0 1 0 1 1 1 0 1 1 1 (3) A B Y (4) A B Y 0 0 0 0 0 0 0 1 0 0 1 1 1 0 0 1 0 1 1 1 1 1 1 1

Q20.The correct relation between α (ratio of collector current to emitter current) and β (ratio of collector current to base current) of a transistor is : (1) β = 1+αα (2) α = 1−αβ (3) β = 1−α1 (4) α = 1+ββ JEE Main 2021 (18 Mar Shift 2) JEE Main Previous Year Paper

Q20.LED is constructed from Ga −As −P semiconducting material. The energy gap of this LED is 1. 9 eV . Calculate the wavelength of light emitted and its colour. h = 6. 63 × 10−34 J −s and c = 3 × 108 m s−1 (1) 654 nm and red colour (2) 654 nm and orange colour (3) 1046 nm and red colour (4) 1046 nm and blue colour → +

Q20.In amplitude modulation, the message signal 𝑉m ( 𝑡) = 10sin2𝜋× 105𝑡 volts and carrier signal 𝑉C𝑡= 20sin2𝜋× 107𝑡 volts. The modulated signal now contains the message signal with lower side band and upper side band frequency, therefore the bandwidth of modulated signal is 𝛼 kHz. The value of 𝛼 is: (1) 200 kHz (2) 500 kHz (3) 100 kHz (4) 0

Q20.If a message signal of frequency fm is amplitude modulated with a carrier signal of frequency fc and radiated through an antenna, the wavelength of the corresponding signal in air is (1) c (2) c fc−fm fm (3) c (4) c fc fc+fm → → → → → →

Q21.A boy pushes a box of mass 2 kg with a force F = (20ˆi 10ˆj)N on a frictionless surface. If the box was initially at rest, then _______ m is displacement along the x -axis after 10 s JEE Main 2021 (26 Feb Shift 1) JEE Main Previous Year Paper

Q21.If P × Q = Q × P , the angle between P and Q is θ(0°< θ < 360°). The value of θ will be ___ ° .

Q21.If the velocity of a body related to displacement x is given by v = √5000 + 24x m s−1, then the acceleration of the body is _________ m s−2.

Q21.The coefficient of static friction between a wooden block of mass 0 . 5 kg and a vertical rough wall is 0 . 2 . The magnitude of the horizontal force that should be applied on the block to keep it adhere to the wall will be______N. 𝑔= 10 m s-2

Q21.Two solids A and B of mass 1 kg and 2 kg respectively are moving with equal linear momentum. The ratio of their kinetic energies (K. E. )A : (K. E. )B will be A1 , so the value of A will be _________.

Q21.The resistance R = VI , where V = (50 ± 2) V and I = (20 ± 0. 2) A . The percentage error in R is x % . The value of x to the nearest integer is ________.

Q22.Two persons A and B perform same amount of work in moving a body through a certain distance d with application of forces acting at angles 45° and 60° with the direction of displacement respectively. The ratio of force applied by person A to the force applied by person B is 1 . The value of x is _________. √x

Q22.A solid disc of radius 20 cm and mass 10 kg is rotating with an angular velocity of 600 rpm, about an axis normal to its circular plane and passing through its centre of mass. The retarding torque required to bring the disc at rest in 10 s is _________ π × 10−1 N m

Q22.A bullet of mass 0. 1 kg is fired on a wooden block to pierce through it, but it stops after moving a distance of 50 cm into it. If the velocity of the bullet before hitting the wood is 10 m s−1 and, it slows down with uniform deceleration, then the magnitude of effective retarding force on the bullet is x N. The value of x to the nearest integer is,

Q22.A person standing on a spring balance inside a stationary lift measures 60 kg . The weight of that person if the lift descends with uniform downward acceleration of 1. 8 m s−2 will be N. [g = 10 m s−2]

Q22.Two particles having masses 4 g and 16 g respectively are moving with equal kinetic energies. The ratio of the magnitudes of their linear momentum is n : 2 . The value of n will be ___.

Q22.The angular speed of truck wheel is increased from 900 rpm to 2460 rpm in 26 seconds. The number of revolutions by the truck engine during this time is ______. (Assuming the acceleration to be uniform).

Q23.A body rotating with an angular speed of 600 rpm is uniformly accelerated to 1800 rpm in 10 sec. The number of rotations made in the process is

Q23.As shown in the figure, a particle of mass 10 kg is placed at a point A. When the particle is slightly displaced to its right, it starts moving and reaches the point B. The speed of the particle at B is x m s−1 . (Take g = 10 m s−2) The value of x to the nearest integer is

Q24.A particle executes S.H.M. with amplitude A and time period T . The displacement of the particle when its speed is half of maximum speed is √xA 2 . The value of x is

Q24.The root-mean-square speed of molecules of a given mass of a gas at 27 °C and 1 atmosphere pressure is 200 m s−1. The root-mean-square speed of molecules of the gas at 127 °C and 2 atmosphere pressure is x m s−1. The value of x will be __________. √3

Q24.A pendulum bob has a speed of 3 m s-1 at its lowest position. The pendulum is 50 cm long. The speed of bob, when the length makes an angle of 60° to the vertical will be 𝑔= 10 m s-2 ______ m s-1. JEE Main 2021 (25 Jul Shift 1) JEE Main Previous Year Paper