Practice Questions

Q26.A rectangular parallelopiped is measured as 1 cm × 1 cm × 100 cm. If its specific resistance is 3 × 10-7Ω m, then the resistance between its two opposite rectangular faces will be _____ × 10-7Ω.

Q26.An electron accelerated through a potential difference V1 has a de-Broglie wavelength of λ. When the potential is changed to V2 , its de-Broglie wavelength increases by 50%. The value of ( V1V2 ) is equal to : JEE Main 2023 (30 Jan Shift 2) JEE Main Previous Year Paper (1) 3 (2) 49 (3) 3 (4) 4 2

Q27.An electron in a hydrogen atom revolves around its nucleus with a speed of 6. 76 × 106 m s–1 in an orbit of radius 0. 52 Å. The magnetic field produced at the nucleus of the hydrogen atom is _______ T.

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.The ratio of wavelength of spectral lines Hα and Hβ in the Balmer series is 20x . The value of x is _____.

Q27.Substance A has atomic mass number 16 and half life of 1 day. Another substance B has atomic mass number 32 and half life of 21 day. If both A and B simultaneously start undergo radio activity at the same time with initial mass 320 g each, how many total atoms of A and B combined would be left after 2 days (1) 3. 38 × 1024 (2) 6. 76 × 1024 (3) 6. 76 × 1023 (4) 1. 69 × 1024

Q27.The ratio of the de-Broglie wavelengths of proton and electron having same kinetic energy: (Assume mp = me × 1849 ) (1) 1 : 43 (2) 1 : 30 (3) 1 : 62 (4) 2 : 43

Q27.A 12. 5 eV electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be: (1) 1 (2) 4 (3) 2 (4) 3

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)

Q27.Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R Assertion A : The nuclear density of nuclides 105B, 63Li, 5626Fe, 2010Ne and 20983Bi can be arranged as ρNBi > ρNFe > ρNNe > ρNB > ρNLi Reason R : The radius R of nucleus is related to its mass number A as R = R0 A 1 3 , where R0 is a constant. In the light of the above statement, choose the correct answer from the options given below : (1) Both A and R are true and R is the correct (2) A is false but R is true explanation of A (3) A is true but R is false (4) Both A and R are true but R is NOT the correct explanation of A

Q27.A beam of light consisting of two wavelengths 7000 A and 5500 A is used to obtain interference pattern in Young's double slit experiment. The distance between the slits is 2. 5 mm and the distance between the plane of slits and the screen is 150 cm. The least distance from the central fringe, where the bright fringes due to both the wavelengths coincide, is n × 10–5 m. The value of n is _____.

Q27.A straight wire AB of mass 40 g and length 50 cm is suspended by a pair of flexible leads in uniform magnetic field of magnitude 0 . 40 T as shown in the figure. The magnitude of the current required in the wire to remove the tension in the supporting leads is _____ A. (Take 𝑔= 10 m s-2.

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.A photon is emitted in transition from n = 4 to n = 1 level in hydrogen atom. The corresponding wavelength for this transition is (given, h = 4 × 10−15 eV s ) (1) 941 nm (2) 974 nm (3) 99. 3 nm (4) 94. 1 nm

Q27.The wavelength of the radiation emitted is λ0 when an electron jumps from the second excited state to the first excited state of hydrogen atom. If the electron jumps from the third excited state to the second orbit of the hydrogen atom, the wavelength of the radiation emitted will be 20 x λ0 . The value of x is________.

Q27.Two identical cells, when connected either in parallel or in series gives same current in an external resistance 5 Ω. The internal resistance of each cell will be ______ Ω.

Q27.In the circuit diagram shown in figure given below, the current flowing through resistance 3 Ω is A. The 3 value of 𝑥 is ________. JEE Main 2023 (11 Apr Shift 1) JEE Main Previous Year Paper

Q27.In an experiment for estimating the value of focal length of converging mirror, image of an object placed at 40 cm from the pole of the mirror is formed at distance 120 cm from the pole of the mirror. These distances are measured with a modified scale in which there are 20 small divisions in 1 cm. The value of error in 1 measurement of focal length of the mirror is cm. The value of 𝐾 is ______. 𝐾

Q27.A charge particle of 2 μC accelerated by a potential difference of 100 V enters a region of uniform magnetic field of magnitude 4 mT at right angle to the direction of field. The charge particle completes semicircle of radius 3 cm inside magnetic field. The mass of the charge particle is ______ × 10-18 kg.

Q27.A straight wire carrying a current of 14 A is bent into a semicircular arc of radius 2 . 2 cm as shown in the figure. The magnetic field produced by the current at the centre 𝑂 of the arc is ____ × 10 – 4 T JEE Main 2023 (10 Apr Shift 2) JEE Main Previous Year Paper

Q27.A hollow cylindrical conductor has length of 3 . 14 m, while its inner and outer diameters are 4 mm and 8 mm respectively. The resistance of the conductor is n × 10-3 𝛺. If the resistivity of the material is 2 . 4 × 10-8 𝛺 m. The value of n 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.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 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.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 .