Practice Questions

Q30.The maximum and minimum amplitude of an amplitude modulated wave is 16 V and 8 V respectively. The modulation index for this amplitude modulated wave is x × 10−2 . The value of x is _______. (Round off your answer to the nearest integer) JEE Main 2021 (26 Feb Shift 1) JEE Main Previous Year Paper

Q30.A message signal of frequency 20 kHz and peak voltage of 20 V is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 V. The modulation index will be:

Q30.An audio signal 𝑣𝑚= 20sin2𝜋1500𝑡 amplitude modulates a carrier 𝑣𝑐= 80sin2𝜋100, 000𝑡. The value of percent modulation is

Q30.For the forward biased diode characteristics shown in the figure, the dynamic resistance at ID = 3 mA will be ________ Ω. JEE Main 2021 (20 Jul Shift 2) JEE Main Previous Year Paper

Q30.A carrier wave VC(t) = 160 sin(2π × 106t) volts is made to vary between Vmax = 200 V and Vmin = 120 V by a message signal Vm(t) = Am sin(2π × 103t) volts. The peak voltage Am of the modulating signal is,

Q30.In the logic circuit shown in the figure, if input A and B are 0 to 1 respectively, the output at Y would be x. The value of x is _________.

Q30.A carrier wave with amplitude of 250 V is amplitude modulated by a sinusoidal base band signal of amplitude 150 V . The ratio of minimum amplitude to maximum amplitude for the amplitude modulated wave is 50: 𝑥, then value of 𝑥, is _________ .

Q30.The maximum amplitude for an amplitude modulated wave is found to be 12 V while the minimum amplitude is found to be 3 V . The modulation index is 0. 6x where x is _____.

Q31.The correct order of electron gain enthalpy is: (1) S > O > Se > Te (2) O > S > Se > Te (3) S > Se > Te > O (4) Te > Se > S > O

Q1. For the four sets of three measured physical quantities as given below. Which of the following options is correct? (i) A1 = 24.36, B1 = 0.0724, C1 = 256.2 (ii) A2 = 24.44, B2 = 16.082, C2 = 240.2 (iii) A3 = 25.2, B3 = 19.2812, C3 = 236.183 (iv) A4 = 25, B4 = 236.191, C4 = 19.5 (1) A4 + B4 + C4 < A1 + B1 + C1 < A3 + B3 + C3 < A2 + B2 + C2 (2) A1 + B1 + C1 = A2 + B2 + C2 = A3 + B3 + C3 = A4 + B4 + C4 (3) A1 + B1 + C1 < A2 + B2 + C2 = A3 + B3 + C3 < A4 + B4 + C4 (4) A1 + B1 + C1 < A3 + B3 + C3 < A2 + B2 + C2 < A4 + B4 + C4

Q1. Amount of solar energy received on the earth's surface per unit area per unit time is defined a solar constant. Dimension of solar constant is: (1) ML2 T−2 (2) ML0 T−3 (3) M2L0T−1 (4) MLT−2

Q2. A particle of mass m is fixed to one end of a light spring having force constant k and unstretched length l. The other end is fixed. The system is given an angular speed ω about the fixed end of the spring such that it rotates in a circle in gravity free space. Then the stretch in the spring is: (1) mlω2 (2) mlω2 k−ωm k−mω2 (3) mlω2 (4) mlω2 k+mω2 k+mω

Q2. Train A and train B are running on parallel tracks in the opposite directions with speed of 36 km hour−1 and 72 km hour−1 , respectively. A person is walking in train A in the direction opposite to its motion with a speed of 1. 8 km hour−1 . Speed (in m s−1) of this person as observed from train B will be close to: (take the distance between the tracks as negligible) (1) 29. 5 m s−1 (2) 28. 5 m s−1 (3) 31. 5 m s−1 (4) 30. 5 m s−1

Q2. A particle of mass m and charge q is released from rest in a uniform electric field. If there is no other force on the particle, the dependence of its speed v on the distance x travelled by it is correctly given by (graphs are schematic and not drawn to scale) (1) (2) (3) (4)

Q3. Starting from the origin at time t = 0, with initial velocity 5 ⌢j ms−1 , a particle moves in the x - y plane with a constant acceleration of + 4⌢j . At time t, its coordinates are (20 m, y0 m). The values of t and y0 (10⌢i )ms−2 are, respectively: (1) 2 s and 18 m (2) 4 s and 52 m (3) 2 s and 24 m (4) 5 s and 25 m

Q3. Hydrogen ion and singly ionized helium atom are accelerated, from rest, through the same potential difference. The ratio of final speeds of hydrogen and helium ions is close to: (1) 1 : 2 (2) 10 : 7 (3) 2 : 1 (4) 5 : 7

Q5. A balloon filled with helium (32°C and 1 .7 atm) bursts. Immediately after wards the expansion of helium can be considered as : (1) irreversible isothermal (2) irreversible adiabatic (3) reversible adiabatic (4) reversible isothermal

Q6. A fluid is flowing through a horizontal pipe of varying cross-section, with v ms−1 at a point where the pressure is P Pascal. At another point where pressure P2 Pascal its speed is V ms−1 . If the density of the fluid is ρ kg −m−3 and the flow is streamline, then V is equal to + υ2 (1) √Pρ + υ (2) √2Pρ (3) √P2ρ + υ2 (4) √Pρ + υ2

Q6. A satellite is in an elliptical orbit around a planet P. It is observed that the velocity of the satellite when it is farthest from the planet is 6 times less than that when it is closest to the planet. The ratio of distances between the satellite and the planet at closest and farthest points is : (1) 1 : 6 (2) 1 : 3 (3) 1 : 2 (4) 3 : 4

Q6. An ideal fluid flows (laminar flow) through a pipe of non-uniform diameter. The maximum and minimum diameters of the pipes are 6.4cm and 4.8cm , respectively. The ratio of the minimum and the maximum velocities of fluid in this pipe is: (1) 9 (2) √3 16 2 (3) 3 (4) 81 4 256

Q6. A uniform sphere of mass 500 g rolls without slipping on a plane horizontal surface with its centre moving at a speed of 5.00 cm s−1 . Its kinetic energy is: (1) 8.75 × 10−4 J (2) 8.75 × 10−3 J (3) 6.25 × 10−4 J (4) 1.13 × 10−3 J

Q7. The specific heat of water = 4200 J kg–1 K–1 and the latent heat of ice = 3.4 × 105 J k g–1 . 100 grams of ice at 0 oC is placed in 200 g of water at 25 oC. The amount of ice that will melt as the temperature of water reaches 0 oC is close to (in grams) (1) 61.7 (2) 63. 8 (3) 69. 3 (4) 64. 6

Q7. A body is moving in a low circular orbit about a planet of mass M and radius R. The radius of the orbit can be taken to be R itself. Then the ratio of the speed of this body in the orbit to the escape velocity from the planet is: JEE Main 2020 (04 Sep Shift 2) JEE Main Previous Year Paper (1) 1 (2) 2 √2 (3) 1 (4) √2

Q7. Planet A has mass M and radius R. Planet B has half the mass and half the radius of Planet A. If the escape velocities from the Planets A and B are vA and vB, respectively, then vA = n4 . The value of n is: vB (1) 4 (2) 1 (3) 2 (4) 3

Q10.A transverse wave travels on a taut steel wire with a velocity of v when tension in it is 2.06 × 104N. When the tension is changed to T, the velocity changed to 2v . The value of T is close to: (1) 2.50 × 104N (2) 5.15 × 103 N (3) 30.5 × 104 N (4) 10.2 × 102 N