Practice Questions

Q27.An object is placed on the principal axis of convex lens of focal length 10 cm as shown. A plane mirror is placed on the other side of lens at a distance of 20 cm. The image produced by the plane mirror is 5 cm inside the mirror. The distance of the object from the lens is ____ cm.

Q27.A radioactive element 24292X emits two α-particles, one electron and two positrons. The product nucleus is represented by 234PY . The value of P is ______. JEE Main 2023 (29 Jan Shift 1) JEE Main Previous Year Paper

Q27.Two identical circular wires of radius 20 cm and carrying current √2A are placed in perpendicular planes as shown in figure. The net magnetic field at the centre of the circular wires is________ × 10-8T . (Take 𝜋= 3 . 14)

Q28.A 20 cm long metallic rod is rotated with 210 rpm about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field 0. 2 T parallel to the axis exists everywhere. The emf developed between the centre and the ring is _________ mV. JEE Main 2023 (15 Apr Shift 1) JEE Main Previous Year Paper (Take π = 227 )

Q28.In the circuit shown in the figure, the ratio of the quality factor and the band width is _____ s.

Q28.An insulated copper wire of 100 turns is wrapped around a wooden cylindrical core of the cross-sectional area 24 cm2. The two ends of the wire are connected to a resistor. The total resistance in the circuit is 12 Ω. If an externally applied uniform magnetic field in the core along its axis changes from 1 . 5 T in one direction to 1 . 5 T in the opposite direction, the charge flowing through a point in the circuit during the change of magnetic field will be _____ mC.

Q28.A 1 m long metal rod 𝑋𝑌 completes the circuit as shown in figure. The plane of the circuit is perpendicular to the magnetic field of flux density 0 . 15 T. If the resistance of the circuit is 5 Ω, the force needed to move the rod in direction, as indicated, with a constant speed of 4 m s-1 will be _______10 – 3 N.

Q28.A nucleus with mass number 242 and binding energy per nucleon as 7. 6 MeV breaks into two fragment each with mass number 121. If each fragment nucleus has binding energy per nucleon as 8. 1 MeV, the total gain in binding energy is _______ MeV.

Q28.A series LCR circuit is connected to an ac source of 220 V, 50 Hz. The circuit contain a resistance 𝑅= 100 Ω and an inductor of inductive reactance 𝑋𝐿= 79 . 6 Ω. The capacitance of the capacitor needed to maximize the average rate at which energy is supplied will be ______ μF.

Q28.An inductor of 0 . 5 mH, a capacitor of 20 μF and resistance of 20 Ω are connected in series with a 220 V ac source. If the current is in phase with the emf, the amplitude of current of the circuit is √𝑥 A. The value of 𝑥 is-

Q28.Nucleus a having Z = 17 and equal number of protons and neutrons has 1. 2 MeV binding energy per nucleon. Another nucleus B of Z = 12 has total 26 nucleons and 1. 8 MeV binding energy per nucleons. The JEE Main 2023 (01 Feb Shift 2) JEE Main Previous Year Paper difference of binding energy of B and A will be ______ MeV.

Q28.The energy released per fission of nucleus of 240X is 200 MeV . The energy released if all the atoms in 120 g of pure 240X undergo fission is _____ ×1025 MeV . (Given NA = 6 × 1023 )

Q28.An ideal transformer with purely resistive load operates at 12 kV on the primary side. It supplies electrical energy to a number of nearby houses at 120 V . The average rate of energy consumption in the houses served by the transformer is 60 kW . The value of resistive load ( 𝑅𝑠) required in the secondary circuit will be _________mΩ .

Q28.A common example of alpha decay is 23892U →23490 Th +2 He4 + Q Given: 23892U = 238. 05060 u 23490Th = 234. 04360 u 42He = 4. 00260 u and 1u = 931. 5 MeVc2 The energy released (Q) during the alpha decay of 23892U is _____ MeV.

Q28.A radioactive nucleus decays by two different process. The half life of the first process is 5 minutes and that of the second process is 30 s. The effective half-life of the nucleus is calculated to be 11α s. The value of α is ______.

Q28.If the binding energy of ground state electron in a hydrogen atom is 13. 6 eV , then, the energy required to remove the electron from the second excited state of Li 2+ will be: x × 10−1 eV . The value of x is _____.

Q28.The magnetic field B crossing normally a square metallic plate of area 4 m2 is changing with time as shown in figure. The magnitude of induced emf in the plate during 𝑡= 2 s to 𝑡= 4 s, is _____ 𝑚𝑉.

Q28.A square loop of side 2 . 0 cm is placed inside a long solenoid that has 50 turns per centimetre and carries a sinusoidally varying current of amplitude 2 . 5 A and angular frequency 700 rad s-1. The central axes of the loop and solenoid coincide. The amplitude of the emf induced in the loop is 𝑥× 10-4 V. The value of 𝑥 is ___________ ( Take, 𝜋= 22 7

Q28.In Young’s double slit experiment, two slits 𝑆1 and 𝑆2 are 𝑑 distance apart and the separation from slits to screen is 𝐷 (as shown in figure). Now if two transparent slabs of equal thickness 0 . 1 mm but refractive index 1 . 51 and 1 . 55 are introduced in the path of beam λ = 4000 Å from 𝑆1 and 𝑆2 respectively. The central bright fringe spot will shift by ________ number of fringes.

Q29.A bi convex lens of focal length 10 cm is cut in two identical parts along a plane perpendicular to the principal axis. The power of each lens after cut is _____ D.

Q29.A point object 𝑂 is placed in front of two thin symmetrical coaxial convex lenses 𝐿1 and 𝐿2 with focal length 24 cm and 9 cm respectively. The distance between two lenses is 10 cm and the object is placed 6 cm away from lens 𝐿1 as shown in the figure. The distance between the object and the image formed by the system of two lenses is _____________ cm

Q29.The refractive index of a transparent liquid filled in an equilateral hollow prism is √2. The angle of minimum deviation for the liquid will be _______ °.

Q29.In a medium the speed of light wave decreases to 0 . 2 times to its speed in free space. The ratio of relative permittivity to the refractive index of the medium is 𝑥: 1. The value of 𝑥 is ______. (Given speed of light in free space = 3 × 108 m s-1 and for the given medium 𝜇𝑟= 1)

Q29.A thin cylindrical rod of length 10 cm is placed horizontally on the principle axis of a concave mirror of focal length 20 cm. The rod is placed in a such a way that mid point of the rod is at 40 cm from the pole of mirror. The length of the image formed by the mirror will be 𝑥 cm. The value of 𝑥 is ______. 3

Q29.As shown in the figure, a combination of a thin plano-concave lens and a thin plano-convex lens is used to image an object placed at infinity. The radius of curvature of both the lenses is 30 cm and refraction index of the material for both the lenses is 1 . 75. Both the lenses are placed at distance of 40 cm from each other. Due to the combination, the image of the object is formed at distance x = ______ cm, from concave lens.