Practice Questions

Q20.A modulating signal is a square wave, as shown in the figure. If the carrier wave is given as ct = 2sin8𝜋t volts, the modulation index is: 1 (1) (2) 1 4 (3) 1 (4) 1 3 2

Q20.A sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of 120 V and 80 V respectively. The amplitude of each side band is : (1) 15 V (2) 10 V (3) 20 V (4) 5 V

Q20.Which of the following frequencies does not belong to FM broadcast. (1) 106 𝑀𝐻𝑧 (2) 64 𝑀𝐻𝑧 (3) 99 𝑀𝐻𝑧 (4) 89 𝑀𝐻𝑧

Q20.A long conducting wire having a current I flowing through it, is bent into a circular coil of N turns. Then it is bent into a circular coil of n turns. The magnetic field is calculated at the centre of coils in both the cases. The ratio of the magnetic field in first case to that of second case is: (1) N : n (2) n2 : N 2 (3) N 2 : n2 (4) n : N

Q21.In an ac generator, a rectangular coil of 100 turns each having area 14 × 10–2 m2 is rotated at 360 rev min−1 about an axis perpendicular to a uniform magnetic field of magnitude 3. 0 T. The maximum value of the emf produced will be ______ V . [Take π = 227 ]

Q21.A metallic rod of length L is rotated with an angular speed of ω normal to a uniform magnetic field B about an axis passing through one end of rod as shown in figure. The induced emf will be : . (1) 1 B2L2ω (2) 1 BL2ω 2 4 (3) 1 BL2ω (4) 1 B2Lω 2 4

Q21.The speed of a swimmer is 4 km h-1 in still water. If the swimmer makes his strokes normal to the flow of river of width 1 km, he reaches a point 750 m down the stream on the opposite bank. The speed of the river water is ______ km h-1.

Q21.For the given figures, choose the correct options: (1) The rms current in circuit (b) can never be larger (2) The rms current in figure (a) is always equal to than that in (a) that in figure (b) (3) The rms current in circuit (b) can be larger than (4) At resonance, current in (b) is less than that in (a) that in (a)

Q21.In the given figure, an inductor and resistor are connected in series with a battery of emf E volt. Ea2b J s−1 represents the maximum rate at which the energy is stored in the magnetic field (inductor). The numerical value of b will be _____. a JEE Main 2023 (13 Apr Shift 1) JEE Main Previous Year Paper

Q21.For a moving coil galvanometer, the deflection in the coil is 0. 05 rad when a current of 10 mA is passed through it. If the torsional constant of suspension wire is 4. 0 × 10–5 N m rad−1 , the magnetic field is 0. 01 T and the number of turns in the coil is 200 , the area of each turn (in cm2 ) is : (1) 2. 0 (2) 1. 0 (3) 1. 5 (4) 0. 5

Q21.A projectile fired at 30° to the ground is observed to be at same height at time 3 s and 5 s after projection, during its flight. The speed of projection of the projectile is m s-1. (Given 𝑔= 10 m s-2) →

Q21.A proton with a kinetic energy of 2. 0 eV moves into a region of uniform magnetic field of magnitude π 2 × 10−3 T. The angle between the direction of magnetic field and velocity of proton is 60o . The pitch of the helical path taken by the proton is ____ cm. (Take, mass of proton = 1. 6 × 10−27 kg and charge on proton = 1. 6 × 10−19 C).

Q21.A closed circular tube of average radius 15 cm, whose inner walls are rough, is kept in vertical plane. A block of mass 1 kg just fit inside the tube. The speed of block is 22 m s-1, when it is introduced at the top of tube. After completing five oscillations, the block stops at the bottom region of tube. The work done by the tube on the block is ________ J. (Given 𝑔= 10 m s-2).

Q21.A certain elastic conducting material is stretched into a circular loop. It is placed with its plane perpendicular to a uniform magnetic field B = 0. 8 T . When released the radius of the loop starts shrinking at a constant rate of 2 cm s–1 . The induced emf in the loop at an instant when the radius of the loop is 10 cm will be ______ mV.

Q21.A horse rider covers half the distance with 5 m s-1 speed. The remaining part of the distance was travelled with speed 10 m s-1 for half the time and with speed 15 m s-1 for other half of the time. The mean 𝑥 speed of the rider averaged over the whole time of motion is m s-1. The value of 𝑥 is ______. 7

Q21.As shown in the figure, a long straight conductor with semicircular arc of radius π m is carrying current 10 I = 3A . The magnitude of the magnetic field. at the center O of the arc is: (The permeability of the vacuum = 4π × 10−7 NA−2 ) (1) 6 μT (2) 1 μT (3) 4 μT (4) 3 μT

Q21.If the maximum load carried by an elevator is 1400 kg ( 600 kg-Passengers + 800 kg-elevator ) , which is moving up with a uniform speed of 3 m s-1 and the frictional force acting on it is 2000 N, then the maximum power used by the motor is _____________kW . 𝑔= 10 m s-2

Q22.A particle of mass 10 g moves in a straight line with retardation 2𝑥, where 𝑥 is the displacement in SI units. 10 -𝑛 Its loss of kinetic energy for above displacement is J . The value of 𝑛 will be ________ . 𝑥

Q22.An LCR series circuit of capacitance 62. 5 nF and resistance of 50 Ω, is connected to an A.C. source of frequency 2. 0 kHz . For maximum value of amplitude of current in circuit, the value of inductance is ____ mH . (Take π2 = 10)

Q22.If the earth suddenly shrinks to 1 of its original volume with its mass remaining the same, the period of 64th 24 rotation of earth becomes 𝑥ℎ. The value of 𝑥 is ________

Q22.A solid sphere and a solid cylinder of same mass and radius are rolling on a horizontal surface without slipping. The ratio of their radius of gyrations respectively (ksph : kcyl) is 2 : √x. The value of x is _______.

Q22.Two concentric circular coils with radii 1 cm and 1000 cm and number of turns 10 and 200 respectively are placed coaxially with centers coinciding. The mutual inductance of this arrangement will be _____ ×10–8 H . (Take, π2 = 10 )

Q22.A spherical body of mass 2 kg starting from rest acquires a kinetic energy of 10000 J at the end of 5th second. The force acted on the body is _____ N.

Q22.Three identical resistors with resistance R = 12 Ω and two identical inductors with sell inductance L = 5 mH are connected to an ideal battery with emf of 12 V as shown in figure. The current through the battery long after the switch has been closed will be________ A. JEE Main 2023 (24 Jan Shift 2) JEE Main Previous Year Paper

Q22.A light rope is wound around a hollow cylinder of mass 5 kg and radius 70 cm. The rope is pulled with a force of 52 . 5 N. The angular acceleration of the cylinder will be _____ rad s-2.