Practice Questions

Q29. X different wavelength may be observed in the spectrum from a hydrogen sample if the atoms are excited to states with principal quantum number n = 6? The value of X is

Q29.A bandwidth of 6 MHz is available for 𝐴. 𝑀. transmission. If the maximum audio signal frequency used for modulating the carrier wave is not to exceed 6 kHz . The number of stations that can be broadcasted within this band simultaneously without interfering with each other will be __________. JEE Main 2021 (31 Aug Shift 2) JEE Main Previous Year Paper

Q29.The energy dissipated by a resistor is 10 mJ in 1 s, when an electric current of 2 mA flows through it. The resistance is ________ Ω. (Round off to the Nearest Integer)

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.A carrier wave with amplitude of 250 V is amplitude modulated by a sinusoidal base band signal of amplitude 150 V . The ratio of minimum amplitude to maximum amplitude for the amplitude modulated wave is 50: 𝑥, then value of 𝑥, is _________ .

Q30.A message signal of frequency 20 kHz and peak voltage of 20 V is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 V. The modulation index will be:

Q30.An audio signal 𝑣𝑚= 20sin2𝜋1500𝑡 amplitude modulates a carrier 𝑣𝑐= 80sin2𝜋100, 000𝑡. The value of percent modulation 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.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.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 amplitude-modulated wave is represented by, Cm(t) = 10(1 + 0. 2 cos 12560t) sin(111 × 104t) V. The modulating frequency in kHz will be JEE Main 2021 (26 Aug Shift 1) JEE Main Previous Year Paper

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

Q31.The correct order of electron gain enthalpy is: (1) S > O > Se > Te (2) O > S > Se > Te (3) S > Se > Te > O (4) Te > Se > S > O

Q51.The number of atoms in 8 g of sodium is 𝑥× 1023 . The value of 𝑥 is _____ . (Nearest integer) Given : NA = 6 . 02 × 1023 mol-1 Atomic mass of Na = 23 . 0u]

Q51.The number of significant figures in 50000. 020 × 10−3 is

Q51.The number of significant figures in 0. 00340 is _________

Q51.The Azimuthal quantum number for the valence electrons of Ga+ ion is (Atomic number of Ga = 31)

Q51.The value of magnetic quantum number of the outermost electron of Zn+ ion is _________ . (Integer answer) JEE Main 2021 (31 Aug Shift 2) JEE Main Previous Year Paper

Q52.A proton and a Li3 + nucleus are accelerated by the same potential. If 𝜆Li and 𝜆p denote the de Broglie + 𝜆Li wavelengths of Li3 and proton respectively, then the value of is 𝑥× 10-1. The value of x 𝜆p is _____ (Rounded off to the nearest integer) [Mass of Li3 + = 8 . 3 mass of proton]

Q52.The number of orbitals with n = 5, m1 = +2 is ________. (Round off to the Nearest Integer).

Q52.Number of electrons that Vanadium (Z = 23) has in p-orbitals is equal to:

Q52.According to the following figure, the magnitude of the enthalpy change of the reaction A + B →M + N in kJ mol−1 is equal to __________ . (Integer answer)

Q52.For water Δvap H = 41 kJ mol−1 at 373 K and 1 bar pressure. Assuming that water vapour is an ideal gas that occupies a much larger volume than liquid water, the internal energy change during evaporation of water is (kJmol−1) : [ Use : R = 8. 3 J mol−1 K−1]

Q53.If the standard molar enthalpy change for combustion of graphite powder is −2. 48 × 102 kJ mol−1 , the amount of heat generated on combustion of 1 g of graphite powder in kJ (Nearest integer):