Practice Questions

Q30.For the forward biased diode characteristics shown in the figure, the dynamic resistance at ID = 3 mA will be ________ Ω. JEE Main 2021 (20 Jul Shift 2) JEE Main Previous Year Paper

Q30.An audio signal 𝑣𝑚= 20sin2𝜋1500𝑡 amplitude modulates a carrier 𝑣𝑐= 80sin2𝜋100, 000𝑡. The value of percent modulation is

Q30.Student 𝐴 and student 𝐵 used two screw gauges of equal pitch and 100 equal circular divisions to measure the radius of a given wire. The actual value of the radius of the wire is 0 . 322 cm. The absolute value of the difference between the final circular scale readings observed by the students 𝐴 and 𝐵 is _______. [Figure shows position of reference 𝑂 when jaws of screw gauge are closed] Given pitch = 0 . 1 cm.

Q30.If the highest frequency modulating a carrier is 5 kHz, then the number of AM broadcast stations accommodated in a 90 kHz bandwidth are

Q30.For VHF signal broadcasting, _______ km2 of maximum service area will be covered by an antenna tower of height 30 m, if the receiving antenna is placed at ground. Let radius of the earth be 6400 km. (Round off to the Nearest Integer) (Take π as 3. 14 )

Q30.A particle of mass m moves in a circular orbit in a central potential field U(r) = U0r4. If Bohr's quantization α , where α is _______ . conditions are applied, radii of possible orbitals rn vary with n 1

Q30.A transmitting antenna has a height of 320 m and that of receiving antenna is 2000 m. The maximum distance between them for satisfactory communication in line of sight mode is d. The value of d is ________ km. = nRT is:

Q30.In the logic circuit shown in the figure, if input A and B are 0 to 1 respectively, the output at Y would be x. The value of x is _________.

Q30.The wavelength of an X-ray beam is 10 Å . The mass of a fictitious particle having the same energy as that of the X-ray photons is x h kg. The value of x is ___ . ( h =Planck's constant) 3

Q30.The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is

Q30.The maximum and minimum amplitude of an amplitude modulated wave is 16 V and 8 V respectively. The modulation index for this amplitude modulated wave is x × 10−2 . The value of x is _______. (Round off your answer to the nearest integer) JEE Main 2021 (26 Feb Shift 1) JEE Main Previous Year Paper

Q30.The maximum amplitude for an amplitude modulated wave is found to be 12 V while the minimum amplitude is found to be 3 V . The modulation index is 0. 6x where x is _____.

Q30.A carrier wave VC(t) = 160 sin(2π × 106t) volts is made to vary between Vmax = 200 V and Vmin = 120 V by a message signal Vm(t) = Am sin(2π × 103t) volts. The peak voltage Am of the modulating signal is,

Q30.For the given circuit, the power across zener diode is _____ mW .

Q30.A signal of 0. 1 kW is transmitted in a cable. The attenuation of cable is −5 dB per km and cable length is 20 km. The power received at the receiver is 10−x W. The value of x is _________. [Gain in dB = 10 log10( POPi )]

Q30.An npn transistor operates as a common emitter amplifier with a power gain of 106. The input circuit resistance is 100 Ω and the output load resistance is 10 kΩ. The common emitter current gain β will be (Round off to the Nearest Integer)

Q31.Outermost electronic configuration of a group 13 element, E, is 4 s2, 4p1. The electronic configuration of an element of p-block period-five placed diagonally to element, E is: (1) [Kr]3 d104 s24p2 (2) [Ar]3 d104 s24p2 (3) [Xe]5 d106 s26p2 (4) [Kr]4 d105 s25p2

Q31.Given below are two statements : Statement I : Rutherford's gold foil experiment cannot explain the line spectrum of hydrogen atom. Statement II : Bohr's model of hydrogen atom contradicts Heisenberg's uncertainty principle. In the light of the above statements, choose the most appropriate answer from the options given below: (1) Statement I is false but statement II is true. (2) Statement I is true but statement II is false. (3) Both statement I and statement II are false. (4) Both statement I and statement II are true.

Q31.Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Metallic character decreases and non-metallic character increases on moving from left to right in a period. Reason (R): It is due to increase in ionisation enthalpy and decrease in electron gain enthalpy, when one moves JEE Main 2021 (31 Aug Shift 1) JEE Main Previous Year Paper from left to right in a period. In the light of the above statements, choose the most appropriate answer from the options given below : (1) (A) is false but (R) is true. (2) Both (A) and (R) are correct and (R) is the correct explanation of (A) (3) Both (A) and (R) are correct but (R) is not the correct explanation of (A). (4) (A) is true but (R) is false.

Q31.The spin only magnetic moments (in BM) for free Ti3+, V2+ and Sc3+ ions respectively are (At.No. Sc : 21, Ti : 22, V : 23 ) (1) 3. 87, 1. 73, 0 (2) 1. 73, 3. 87, 0 (3) 1. 73, 0, 3. 87 (4) 0, 3. 87, 1. 73

Q31.Number of paramagnetic oxides among the following given oxides is ___________ . Li2O, CaO, Na2O2, KO2, MgO and K2O (1) 1 (2) 3 (3) 0 (4) 2

Q31.An inorganic Compound ′X′ on treatment with concentrated H2 SO4 produces brown fumes and gives dark brown ring with FeSO4 in presence of concentrated H2 SO4 . Also Compound ′X′ gives precipitate ′Y′, when its solution in dilute HCl is treated with H2S gas. The precipitate ′Y′ on treatment with concentrated HNO3 followed by excess of NH4 OH further gives deep blue coloured solution, Compound ′X′ is: (1) Co (NO3)2 (2) Pb (NO2)2 (3) Cu (NO3)2 (4) Pb (NO3)2

Q31.Given below are two statements : Statement I : According to Bohr's model of an atom, qualitatively the magnitude of velocity of electron increases with decrease in positive charges on the nucleus as there is no strong hold on the electron by the nucleus. Statement II : According to Bohr's model of an atom, qualitatively the magnitude of velocity of electron increases with decrease in principle quantum number. In the light of the above statements, choose the most appropriate answer from the options given below: (1) Statement I is false but Statement II is true (2) Statement I is true but Statement II is false (3) Both Statement I and Statement II are false (4) Both Statement I and Statement II are true

Q31.According to Bohr's atomic theory: (A) Kinetic energy of electron is ∝Z2 . n2 (B) The product of velocity (v) of electron and principal quantum number (n), ′vn′∝Z2. (C) Frequency of revolution of electron in an orbit is ∝Z3 . n3 (D) Coulombic force of attraction on the electron is ∝Z3 . n4 Choose the most appropriate answer from the options given below: (1) (A), (C) and (D) only (2) (A) and (D) only (3) (C) only (4) (A) only

Q31.Given below are two statements: Statement I : Bohr's theory accounts for the stability and line spectrum of Li+ ion. Statement II : Bohr's theory was unable to explain the splitting of spectral lines in the presence of a magnetic field. In the light of the above statements, choose the most appropriate answer from the options given below: (1) Both statement I and statement II are true. (2) Statement I is false but statement II is true. (3) Both statement I and statement II are false. (4) Statement I is true but statement II is false. JEE Main 2021 (18 Mar Shift 2) JEE Main Previous Year Paper