Practice Questions

Q20.A coil is placed in magnetic field such that plane of coil is perpendicular to the direction of magnetic field. The magnetic flux through a coil can be changed: A. By changing the magnitude of the magnetic field within the coil. B. By changing the area of coil within the magnetic field. C. By changing the angle between the direction of magnetic field and the plane of the coil. D. By reversing the magnetic field direction abruptly without changing its magnitude. Choose the most appropriate answer from the options given below: (1) A and B only (2) A, B and C only (3) A, B and D only (4) A and C only

Q20.Two cells are connected between points A and B as shown. Cell 1 has emf of 12 V and internal resistance of 3 Ω. Cell 2 has emf of 6 V and internal resistance of 6 Ω. An external resistor R of 4 Ω is connected across A and B. The current flowing through R will be ______ A .

Q20.By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21%? (1) 15% (2) 12% (3) 10% (4) 14%

Q20.A solenoid of 1200 turns is wound uniformly in a single layer on a glass tube 2 m long and 0. 2 m in diameter. The magnetic intensity at the center of the solenoid when a current of 2 A flows through it is: (1) 2. 4 × 103 A m−1 (2) 1. 2 × 103 A m−1 (3) 1 A m−1 (4) 2. 4 × 10−3 A m−1

Q20.Certain galvanometers have a fixed core made of non magnetic metallic material. The function of this metallic material is JEE Main 2023 (08 Apr Shift 1) JEE Main Previous Year Paper (1) to oscillate the coil in magnetic field for longer (2) to bring the coil to rest quickly period of time (3) to produce large deflecting torque on the coil (4) to make the magnetic field radial

Q20.A single turn current loop in the shape of a right angle triangle with sides 5 cm, 12 cm, 13 cm is carrying a current of 2 A . The loop is in a uniform magnetic field of magnitude 0. 75 T whose direction is parallel to the current in the 13 cm side of the loop. The magnitude of the magnetic force on the 5 cm side will be 130x N . The value of x is _______.

Q20.The ratio of magnetic field at the centre of a current carrying coil of radius r to the magnetic field at distance r from the centre of coil on its axis is √x : 1 . The value of x is _____.

Q20.The amplitude of 15sin ( 1000π𝑡) is modulated by 10sin ( 4π𝑡) signal. The amplitude modulated signal contains frequency (ies) of ( 𝐴) 500 Hz ( 𝐵) 2 Hz ( 𝐶) 250 Hz ( 𝐷) 498 Hz ( 𝐸) 502 Hz Choose the correct answer from the options given below: (1) A only (2) A, D and E only (3) B only (4) A and B only

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

Q20.A carrier wave of amplitude 15 V is modulated by a sinusoidal base band signal of amplitude 3 V. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is 3 (1) 2 (2) 2 (3) 1 (4) 5

Q21.A charge particle moving in magnetic field B, has the components of velocity along B as well as perpendicular to B. The path of the charge particle will be (1) helical path with the axis perpendicular to the (2) helical path with the axis along magnetic field B direction of magnetic field B (3) circular path (4) straight along the direction of magnetic field B

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.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.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 block of mass 10 kg is moving along x-axis under the action of force F = 5x N . The work done by the force in moving the block from x = 2 m to 4 m will be _______ J.

Q21.A car accelerates from rest of 𝑢 m s-1. The energy spent in this process is 𝐸 J. The energy required to accelerate the car from 𝑢 m s-1 to 2𝑢 m s-1 is 𝑛𝐸 J. The value of 𝑛 is _____. JEE Main 2023 (13 Apr Shift 2) JEE Main Previous Year Paper

Q21.An emf of 0. 08 V is induced in a metal rod of length 10 cm held normal to a uniform magnetic field of 0. 4 T, when move with a velocity of: (1) 0. 5 m s−1 (2) 20 m s−1 (3) 3. 2 m s−1 (4) 2 m s−1

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

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.Vectors 𝑎 ^𝑖+ 𝑏 ^𝑗+ ^𝑘 and 2 ^𝑖- 3 ^𝑗+ 4 ^𝑘 are perpendicular to each other when 3𝑎+ 2𝑏= 7, the ratio of 𝑎 to 𝑏 is 𝑥 2. The value of 𝑥 is _____.

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 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.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.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.The length of a metallic wire is increased by 20% and its area of cross-section is reduced by 4 % . The percentage change in resistance of the metallic wire is ________ .