Practice Questions

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)

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.If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160 m, then the maximum range of LOS communication is _______ km (Take radius of Earth = 6400 km)

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 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 amplitude of upper and lower side bands of AM wave where a carrier signal with frequency 11. 21 MHz, peak voltage 15 V is amplitude modulated by a 7. 7 kHz sine wave of 5 V amplitude are 10a V and 10b V respectively. Then the value of a is_____. b JEE Main 2021 (27 Jul Shift 1) JEE Main Previous Year Paper

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

Q30.A TV transmission tower antenna is at a height of 20 m. Suppose that the receiving antenna is at. (i) ground level (ii) a height of 5 m. The increase in antenna range in case (ii) relative to case (i) is n%. The value of n, to the nearest integer, is.

Q30.A deviation of 2° is produced in the yellow ray when prism of crown and flint glass are achromatically combined. Taking dispersive powers of crown and flint glass are 0. 02 and 0. 03 respectively and refractive JEE Main 2021 (16 Mar Shift 2) JEE Main Previous Year Paper index for yellow light for these glasses are 1. 5 and 1. 6 respectively. The refracting angles for crown glass prism will be ________ ° (in degree) (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.The diameter of a spherical bob is measured using a vernier callipers. 9 divisions of the main scale, in the vernier callipers, are equal to 10 divisions of vernier scale. One main scale division is 1 mm . The main scale reading is 10 mm and 8th division of vernier scale was found to coincide exactly with one of the main scale division. If the given vernier callipers has positive zero error of 0 . 04 cm, then the radius of the bob is _____________ × 10-2 cm .

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.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.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.A zener diode of power rating 2 W is to be used as a voltage regulator. If the zener diode has a breakdown of 10 V and it has to regulate voltage fluctuated between 6 V and 14 V , the value of Rs for safe operation should be _____ Ω .

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.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.In a given circuit diagram, a 5 V zener diode along with a series resistance is connected across a 50 V power supply. The minimum value of the resistance required, if the maximum zener current is 90 mA will be Ω.

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.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 )

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

Q31.Complete combustion of 1. 80 g of an oxygen containing compound (CxHyOz) gave 2. 64 g of CO2 and 1. 08 g of H2O. The percentage of oxygen in the organic compound is : (1) 53. 33 (2) 50. 33 (3) 51. 63 (4) 63. 53

Q53.For the reaction A𝑔→Bg, the value of the equilibrium constant at 300 K and 1 atm is equal to 100 . 0 . The value of ΔGo for the reaction at 300 K and 1 atm in Jmol-1 is -𝑥R, where x is (Rounded off to the nearest integer) R = 8 . 31 J mol-1 K-1 and ln10 = 2 . 3

Q61.The least value of |z| where z is complex number which satisfies the inequality ||z|+1| loge 2) e( (|z|+3)(|z|−1) ≥log√2 5√7 + 9i , i = √−1, is equal to : (1) 3 (2) √5 (3) 2 (4) 8