Practice Questions

Q27.A solution containing active cobalt 6027Co having an activity of 0 .8 μCi and decay constant λ is injected in an animal's body. When 1 cm3 blood is drawn from the animal's body after 10 h of injection, the activity was found to be 300 dpm(decays per minute), then the total volume of blood in the animal's body is close to [1 Ci = 3 .7 ×1010 dps(decays per second) and at t = 10 h the value of e−λt = 0.84] (1) 4 L (2) 6 L (3) 5 L (4) 7 L

Q27.An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let λn, λg be the de Broglie wavelength of the electron in the nth state and the ground state respectively. Let ∧n be the wavelength of the emitted photon in the transition from the nth state to the ground state. For large n, (A, B are constants) (1) ∧2n ≈λ (2) ∧n ≈A + λ2nB (3) ∧n ≈A + Bλn (4) ∧2n ≈A + Bλ2n

Q27.A solution containing active cobalt 6027Co having activity of 0.8μCi and decay constant λ is injected in an animal's body. If 1 cm3 of blood is drawn from the animal's body after 10hrs of injection, the activity found was 300 decays per minute. What is the volume of blood that is flowing in the body? (1Ci = 3.7 × 1010 decay per second and at t = 10hrs−λt = 0.84) (1) 6 litres (2) 7 litres (3) 4 litres (4) 5 litres

Q27.Muon (μ−1) is negatively charged (|q| = |e|) with a mass mμ = 200 me , where me is the mass of the electron and e is the electronic charge. If μ−1 is bound to a proton to form a hydrogen like atom, identify the correct statements (A) Radius of the muonic orbit is 200 times smaller than that of the electron (B) the speed of the μ−1 in the nth orbit is 1 times that of the election in the nth orbit (C) The lonization energy of muonic atom 200 is 200 times more than that of an hydrogen atom (D) The momentum of the muon in the nth orbit is 200 times more than that of the electron (1) (A), (B), (D) (2) (B), (D) (3) (C),(D) (4) (A), (C), (D)

Q27.Both the nucleus and the atom of some element are in their respective first excited states. They get de-excited by emitting photons of wavelengths λN, λA respectively. The ratio λN is closest to: λA (1) 10−1 (2) 10−6 (3) 10 (4) 10−10 JEE Main 2018 (16 Apr Online) JEE Main Previous Year Paper

Q28.In a common emitter configuration with suitable bias, it is given that RL is the load resistance and RBE is small-signal dynamic resistance (input side). Then, voltage gain, current gain and power gain are given, respectively, by: β is current gain, IB , IC and IE are respectively base, collector, and emitter currents. (1) β RL , ΔIC , β2 RL (2) β RL , ΔIE , β2 RL RBE ΔIB RBE RBE ΔIB RBE (3) β2 RL , ΔIC , β RL (4) β2 RL , ΔIC , β2 RL RBE ΔIB RBE RBE ΔIE RBE

Q28.At some instant, a radioactive sample S1 having an activity 5μCi has twice the number of nuclei as another sample S2 which has an activity of 10μCi. The half lives of S1 and S2 are : (1) 4 : 1 (2) 1 : 4 (3) 1 : 2 (4) 2 : 1

Q28.If the series limit frequency of the Lyman series is VL, then the series limit frequency of the Pfund series is: (1) VL25 (2) 25 VL (3) 16 VL (4) VL16

Q28.In a common emitter configuration with suitable bias, it is given than RL is the load resistance and RBE is small signal dynamic resistance (input side). Then, voltage gain, current gain and power gain are given, respectively, by: [ β is current gain, IB, IC, IE are respectively base, collector and emitter currents] (1) β RL , ΔIE , β2 RL (2) β2 RL , ΔIC , β RL RBE ΔIB RBE RBE ΔIB RBE (3) β2 RL , ΔIC , β2 RL (4) β RL , ΔIC , β2 RL RBE ΔIE RBE RBE ΔIB RBE

Q28.An unstable heavy nucleus at rest breaks into two nuclei which move away with velocities in the ratio of 8 : 27 . The ratio of the radii of the nuclei (assumed to be spherical ) is: (1) 8 : 27 (2) 2 : 3 (3) 3 : 2 (4) 4 : 9 JEE Main 2018 (15 Apr Shift 2 Online) JEE Main Previous Year Paper

Q29.The number of amplitude modulated broadcast stations that can be accommodated in a 300kHz band width for the highest modulating frequency 15kHz will be: (1) 20 (2) 10 (3) 8 (4) 15

Q29.The reading of the ammeter for a silicon diode in the given circuit is: (1) 13 .5 mA (2) 0 (3) 15 mA (4) 11 .5 mA

Q29.The number of amplitude-modulated broadcast stations that can be accommodated in a 300 kHz bandwidth for the highest modulating frequency 15 kHz will be: (1) 15 (2) 20 (3) 8 (4) 10

Q29. Truth table for the given circuit will be (1) (2) x y z x y z 0 0 1 0 0 0 0 1 1 0 1 0 1 0 1 1 0 0 1 1 0 1 1 1 (3) (4) x y z x y z 0 0 1 0 0 0 0 1 1 0 1 1 1 0 1 1 0 1 1 1 1 1 1 1

Q29.In the given circuit the current through zener diode is: (1) 3. 3 mA (2) 2. 5 mA (3) 5. 5 mA (4) 6. 7 mA

Q30.A carrier wave of peak voltage 14 V is used for transmitting a message signal. The peak voltage of the modulating signal given to achieve a modulation index of 80% will be: (1) 22 .4 V (2) 7 V (3) 11 .2 V (4) 28 V

Q30.In a screw gauge, 5 complete rotations of the screw cause it to move a linear distance of 0.25 cm. There are 100 circular scale divisions. The thickness of a wire measured by this screw gauge gives a reading of 4 main scale divisions and 30 circular scale divisions. Assuming negligible zero error, the thickness of the wire is: (1) 0.0430 cm (2) 0.3150 cm (3) 0.4300 cm (4) 0.2150 cm

Q30.A telephonic communication service is working at a carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz ? (1) 2 × 106 (2) 2 × 103 (3) 2 × 104 (4) 2 × 105

Q30.In a screw gauge, 5 complete rotations of the screw cause it to move a linear distance of 0. 25 cm. There are 100 circular scale divisions. The thickness of a wire measured by this screw gauge gives a reading of 4 main scale divisions and 30 circular scale divisions. Assuming negligible error, the thickness of the wire is (1) 0. 4300 cm (2) 0. 3150 cm (3) 0. 0430 cm (4) 0. 2150 cm

Q30.The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance 49μH and a capactiance of 2.5nF. It is modulated by an audio signal of 12kHz. The frequency range occupied by the side bands is: (1) 18kHz −30kHz (2) 63kHz −75kHz (3) 442kHz −466kHz (4) 13482kHz −13494kHz

Q31.The ratio of mass percent of C and H of an organic compound (CXHYOZ) is 6 : 1. If one molecule of the above compound (CXHYOZ) contains half as much oxygen as required to burn one molecule of compound CXHY completely to CO2 and H2O. The empirical formula of the compound CXHYOZ is (1) C2H4O3 (2) C3H6O3 (3) C2H4O (4) C3H4O2

Q31.For per gram of reactant, the maximum quantity of N2 gas is produced in which of the following thermal decomposition reactions? (Given: Atomic wt. : Cr = 52u, Ba = 137u ). (1) Ba(N3)2 (s) ⟶Ba(C) + 3 N2( g) (2) (NH4)2Cr2O7( s) ⟶ N2( g) + 4H2O(g) + Cr2O3( s) (3) 2NH3( g) ⟶N2( g) + 3H2( g) (4) 2NH4NO3( s) ⟶ 2 N2( g) + 4H2O(g) + O2( g)

Q31.A sample of NaClO3 is converted by heat to NaCl with a loss of 0. 16 g of oxygen. The residue is dissolved in water and precipitated as AgCl. The mass of AgCl (in g) obtained will be: (Given: Molar mass of AgCl = 143 .5 g mol−1 ) (1) 0. 35 (2) 0. 54 (3) 0. 41 (4) 0. 48

Q31.An unknown chlorohydrocarbon has 3.55 % of chlorine. If each molecule of the hydrocarbon has one chlorine atom only; chlorine atoms present in 1 g of chlorohydrocarbon are :(Atomic wt. of Cl = 35 .5 u; Avogadro constant = 6 .023 ×1023 mol–1 ) (1) 6.023 × 109 (2) 6.023 × 1023 (3) 6.023 × 1021 (4) 6.023 × 1020

Q31.A sample of NaClO3 is converted by heat to NaCl with a loss of 0.16 g of oxygen. The residue is dissolved in water and precipitated as AgCl. The mass of AgCl (in g) obtained will be: (Given: Molar mass of AgCl = 143.5 g mol−1 ) (1) 0.35 (2) 0.54 (3) 0.41 (4) 0.48