Practice Questions

Q20.Two coils 'P' and 'Q' are separated by some distance. When a current of 3 A flows through coil 'P', a magnetic flux of 10−3 Wb passes through 'Q'. No current is passed through 'Q'. When no current passes through 'P' and a current of 2 A passes through 'Q', the flux through 'P' is: (1) 3.67 × 10−3 Wb (2) 6.67 × 10−4 Wb (3) 3.67 × 10−4 Wb (4) 6.67 × 10−3 Wb

Q20.A resistance is shown in the figure. Its value and tolerance are given respectively by: (1) 27 𝑘Ω, 10% (2) 270 Ω, 5% (3) 270 Ω, 10% (4) 27 𝑘Ω, 20%

Q21.A current of 2 mA was passed through an unknown resistor which dissipated a power of 4.4 W. Dissipated power when an ideal power supply of 11 V is connected across it is: (1) 11 × 105 W (2) 11 × 10−3 W (3) 11 × 10−5 W (4) 11 × 10−4 W

Q21.In the figure shown, a circuit contains two identical resistors with resistance R = 5 Ω and an inductance with L = 2 mH. An ideal battery of 15V is connected in the circuit. What will be the current through the battery long after the switch is closed? (1) 5.5 A (2) 6 A (3) 3 A (4) 7.5 A

Q21.A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 𝑚, 100 turns, and carrying a current of 5.2 𝐴. The coercivity of the bar magnet is: JEE Main 2019 (09 Jan Shift 1) JEE Main Previous Year Paper (1) 285 𝐴/ 𝑚 (2) 2600 𝐴/ 𝑚 (3) 520 𝐴/ 𝑚 (4) 1200 𝐴/ 𝑚

Q22.Given below in the left column are different modes of communication using the kinds of waves given in the right column. (1) Optical Fibre Communication (P) Ultrasound (2) Radar (Q) Infrared Light (3) Sonar (R) Microwaves (4) Mobile Phones (S) Radio Waves From the options given below, find the most appropriate match between entries in the left and the right column. (1) 1 −Q, 2 −S, 3 −P, 4 −R (2) 1 − S, 2 −Q, 3 −R, 4 −P (3) 1 −Q, 2 −S, 3 −R, 4 −P (4) 1 −R, 2 −P, 3 −S, 4 −Q

Q23.If the magnetic field of a plane electromagnetic wave is given by (The speed of light = 3 × 108 m/s) B = 100 × 10−6 sin[2π × 2 × 1015(t −xc )] then the maximum electric field associated with it is: (1) 3 × 104 N C−1 (2) 4 × 104 N C−1 (3) 4.5 × 104 N C−1 (4) 6 × 104 N C−1

Q23.The total number of turns and cross-section area in a solenoid is fixed. However, its length L is varied by adjusting the separation between windings. The inductance of solenoid will be proportional to: (1) L (2) 1 L2 (3) 1 (4) L2 L JEE Main 2019 (09 Apr Shift 1) JEE Main Previous Year Paper →

Q23.An electromagnetic wave is represented by the electric filed →E = E0^nsin⁡ωt + 6𝑦- 8𝑧. Taking unit vectors in 𝑥, 𝑦 and 𝑧 directions to be ^𝑖, ^𝑗, ^𝑘, the directions of propogations ^s, is: (1) 3^𝑖- 4^𝑗 (2) -3^𝑖+ 4^𝑗 ^s = ^s = 5 5 4^𝑖- 3^𝑘 -4^𝑖- 3^𝑘 (3) (4) ^s = ^s = 5 5

Q23.A plane electromagnetic wave travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time is E = 6 V m-1 along y-direction. Its corresponding magnetic field component, B would be: (1) 2 × 10-8 T along z- (2) 2 × 10-8 T along y- (3) 6 × 10-8 T along z- (4) 6 × 10-8 T along x- direction direction direction direction

Q23.The energy associated with electric field is (UE) and with magnetic field is (UB) for an electromagnetic wave in free space. Then: (1) UE > UB (2) UE = UB (3) UE = UB2 (4) UE < UB

Q24.A monochromatic light is incident at a certain angle on an equilateral triangular prism and suffers minimum deviation. If the refractive index of the material of the prism is √3, then the angle of incidence is : (1) 90∘ (2) 30∘ (3) 60∘ (4) 45∘

Q25.The eye can be regarded as a single refracting surface. The radius of curvature of this surface is equal to that of the cornea (7 .8 mm). This surface separates two media of refractive indices 1 and 1.34 . Calculate the distance from the refracting surface at which a parallel beam of light will come to focus. JEE Main 2019 (10 Jan Shift 2) JEE Main Previous Year Paper (1) 4 .0 cm (2) 1 cm (3) 2 cm (4) 3.07 cm

Q25.A plane electromagnetic wave of frequency 50 𝑀𝐻𝑧 travels in free space along the positive 𝑥 - direction. At a particular point in space and time, →𝐸= 6.3 ^𝑗 𝑉/ 𝑚, The corresponding magnetic field →𝐵, at that point will be: (1) 2.1 × 10-8^𝑘 𝑇 (2) 18.9 × 108^𝑘 𝑇 (3) 18.9 × 10-8^𝑘 𝑇 (4) 6.3 × 10-8^𝑘 𝑇

Q25.Calculate the limit of resolution of a telescope objective having a diameter of 200 cm , if it has to detect light of wavelength 500 nm coming from a star. (1) 305 × 10-9 radian (2) 610 × 10-9 radian (3) 152.5 × 10-9 radian (4) 457.5 × 10-9 radian

Q25.The value of numerical aperture of the objective lens of a microscope is 1.25 . If light of wavelength 5000 Å is used, the minimum separation between two points, to be seen as distinct, will be: (1) 0.48 μm (2) 0.24 μm (3) 0.38 μm (4) 0.12 μm

Q26.In a photoelectric effect experiment, the threshold wavelength of light is 380 nm . If the wavelength of incident light is 260 nm , the maximum kinetic energy of emitted electrons will be Given E (in eV ) = 1237 λ(in nm) (1) 4.5 eV (2) 3.0 eV (3) 1.5 eV (4) 15.1 eV

Q26.Diameter of the objective lens of a telescope is 250 cm. For light of wavelength 600 nm coming from a distant object, the limit of resolution of the telescope is close to: (1) 1.5 × 10−7 rad (2) 3.0 × 10−7 rad (3) 2.0 × 10−7 rad (4) 4.5 × 10−7 rad

Q27.In a radioactive decay chain, the initial nucleus is 232 90 Th. At the end, there are 6 α-particles and 4β-particles which are emitted. If the end nucleus is AZX, A and Z are given by: (1) A = 208; Z = 82 (2) A = 208; Z = 80 (3) A = 200; Z = 81 (4) A = 202; Z = 80

Q27.The output of the given logic circuit is: (1) − (2) − A B A B ¯(3) AB + AB (4) − − A B + A B

Q27.A 2 mW laser operates at a wavelength of 500 nm . The number of photons that will be emitted per second is: [Given Planck's constant h = 6.6 × 10-34 J s, speed of light c = 3.0 × 108 m / s ] (1) 1.5 × 1016 (2) 5 × 1015 (3) 2 × 1016 (4) 1 × 1016 JEE Main 2019 (10 Apr Shift 2) JEE Main Previous Year Paper

Q28.To get output '1' at R, for the given logic gate circuit the input values must be: (1) X = 1, Y = 1 (2) X = 0, Y = 0 (3) X = 0, Y = 1 (4) X = 1, Y = 0

Q28.The ratio of mass densities of nuclei of 40Ca and 16O is close to: (1) 1 (2) 0.1 (3) 2 (4) 5

Q28.A He+ ion is in its first excited state. Its ionization energy is: (1) 13.60 eV (2) 48.36 eV (3) 54.40 eV (4) 6.04 eV

Q28.A 100V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index? (1) 0.3 (2) 0.6 (3) 0.4 (4) 0.5