Practice Questions

Q27.An AC circuit has an inductor and a resistor of resistance R in series, such that XL = 3R. Now, a capacitor is added in series such that XC = 2R. the ratio of the new power factor with the old power factor of the circuit is √5 : x. The value of x is

Q27.Consider a 72 cm long wire AB as shown in the figure. The galvanometer jockey is placed at P on AB at a distance x cm from A . The galvanometer shows zero deflection. JEE Main 2021 (18 Mar Shift 2) JEE Main Previous Year Paper The value of x, to the nearest integer, is

Q28.In an LCR series circuit, an inductor 30 mH and a resistor 1 Ω are connected to an AC source of angular frequency 300 rad s−1. The value of capacitance for which the current leads the voltage by 45° is 1 × 10−3 F . Then the value of x is x

Q28.A radiation is emitted by 1000 W bulb and it generates an electric field and magnetic field at P , placed at a distance of 2 m . The efficiency of the bulb is 1. 25% . The value of peak electric field at P is x × 10−1 V m−1 . Value of x is (Rounded-off to the nearest integer) [Take ε0 = 8. 85 × 10−12 C2 N−1 m−2, c = 3 × 106 m s−1 ]

Q28.The difference in the number of waves when yellow light propagates through air and vacuum columns of the same thickness is one. The thickness of the air column is _____ mm. [Refractive index of air = 1. 0003, the ∘ wavelength of yellow light in vacuum = 6000 A]

Q28.The nuclear activity of a radioactive element becomes ( 81 ) th radioactive element is ________ years.

Q28.Two wires of same length and thickness having specific resistances 6 Ω cm and 3 Ω cm respectively are connected in parallel. The effective resistivity is ρ Ωcm. The value of ρ to the nearest integer, is ___ .

Q28.An unpolarized light beam is incident on the polarizer of a polarization experiment and the intensity of light beam emerging from the analyzer is measured as 100 Lumens. Now, if the analyzer is rotated around the horizontal axis (direction of light) by 30° in clockwise direction, the intensity of emerging light will be _______Lumens.

Q28.In a parallel plate capacitor set up, the plate area of capacitor is 2 m2 and the plates are separated by 1 m. If the space between the plates are filled with a dielectric material of thickness 0. 5 m and are 2 m2 (see figure) the capacitance of the set-up will be ε0 ________. (Dielectric constant of the material = 3. 2 ) (Round off to the Nearest Integer)

Q28.The equivalent resistance of series combination of two resistors is s. When they are connected in parallel, the equivalent resistance is p. If s = np, then the minimum value for n is ______. (Round off to the Nearest Integer) JEE Main 2021 (17 Mar Shift 1) JEE Main Previous Year Paper

Q28.A coil of inductance 2 H having negligible resistance is connected to a source of supply whose voltage is given by V = 3t volt. (where t is in second). If the voltage is applied when t = 0, then the energy stored in the coil JEE Main 2021 (25 Feb Shift 1) JEE Main Previous Year Paper after 4 s in J ,

Q28.In an electric circuit, a call of certain emf provides a potential difference of 1. 25 V across a load resistance of 5 Ω. However, it provides a potential difference of 1 V across a load resistance of 2 Ω.The emf of the cell is given by x V. Then the value of x is . 10 = √3) suffers minimum deviation. It is found that the angle of

Q28.The circuit shown in the figure consists of a charged capacitor of capacity 3 μF and a charge of 30 μC. At time t = 0, when the key is closed, the value of current flowing through the 5 MΩ resistor is x μA. The value of x to the nearest integer is

Q28.A square-shaped wire with a resistance of each side 3 Ω is bent to form a complete circle. The resistance between two diametrically opposite points of the circle in a unit of Ω will is, _____.

Q28.In a Young's double slit experiment, the slits are separated by 0 . 3 mm and the screen is 1 . 5 m away from the plane of slits. Distance between fourth bright fringes on both sides of central bright fringe is 2 . 4 cm . The frequency of light used is 𝑥× 1014 Hz .

Q28.The first three spectral lines of H-atom in the Balmer series are given λ1, λ2, λ3 considering the Bohr atomic model, the wave lengths of first and third spectral lines ( λ1λ3 ) are related by a factor of approximately x JEE Main 2021 (16 Mar Shift 1) JEE Main Previous Year Paper ×10−1 . The value of x, to the nearest integer, is ________.

Q28.The electric field in a plane electromagnetic wave is given by → E = 200 cos[(0. 5 × 103 m−1)x −(1. 5 × 1011 rad s−1)t] V m−1 ˆj. If this wave falls normally on a perfectly reflecting surface having an area of 100 cm2 . If the radiation pressure exerted by the E.M. wave on the surface during a 10 min exposure is k N m−2 . Find the value of k 109

Q28.The temperature of 3 . 00 mol of an ideal diatomic gas is increased by 40 . 0°C without changing the pressure of the gas. The molecules in the gas rotate but do not oscillate. If the ratio of change in internal energy of the 𝑥 gas to the amount of workdone by the gas is . Then the value of 𝑥 (round off to the nearest integer) is 10 _________ . ( Given𝑅= 8 . 31 J mol-1 K-1

Q29.The zener diode has a Vz = 30 V . The current passing through the diode for the following circuit is___ mA.

Q29.The typical output characteristics curve for a transistor working in the common-emitter configuration is shown in the figure. The estimated current gain from the figure is

Q29.A circuit is arranged as shown in figure. The output voltage Vo is equal to __________ V.

Q29.In a semiconductor, the number density of intrinsic charge carriers at 27°C is 1. 5 × 1016 m−3 . If the semiconductor is doped with an impurity atom, the hole density increases to 4. 5 × 1022 m−3 . The electron density in the doped semiconductor is _______ ×109 m−3

Q29.The image of an object placed in air formed by a convex refracting surface is at a distance of 10 m behind the surface. The image is real and is at 2rd of the distance of the object from the surface. The wavelength of light 3 inside the surface is 2 times the wavelength in air. The radius of the curved surface is x m , the value of x 3 13 is ______ .

Q29.An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2. 25 from vacuum. The wavelength of this wave in that medium will be _________ ×10−2 cm.

Q29.The circuit contains two diodes each with a forward resistance of 50 Ω and with infinite reverse resistance. If the battery voltage is 6 V , the current through the 120 Ω resistance is _______ mA