Practice Questions

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

Q28.The alternating current is given by, i = {√42 sin( 2πT t) 10} __________ A.

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.Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the metal surface successively. The value of ratio of maximum velocities of the photoelectrons emitted in the two respective cases is x : 3 The value of x is

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.An object is placed at a distance of 12 cm from a convex lens. A convex mirror of focal length 15 cm is placed on another side of the lens at 8 cm as shown in the figure. The image of the object coincides with the object. When the convex mirror is removed, a real and inverted image is formed at a position. The distance of the image from the object will be ___ cm JEE Main 2021 (26 Aug Shift 2) JEE Main Previous Year Paper

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.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 circular conducting coil of radius 1 m is being heated by the change of magnetic field →𝐵 passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2 μΩ. The magnetic field is slowly switched off such that its magnitude changes in time as 4 𝑡 𝐵= 𝜋× 10-3 𝑇1 - 100 The energy dissipated by the coil before the magnetic field is switched off completely is 𝐸= ______mJ.

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 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.A radioactive sample has an average life of 30 ms and is decaying. A capacitor of capacitance 200 μF is first charged and later connected with resistor R. If the ratio of the charge on the capacitor to the activity of the radioactive sample is fixed with respect to time then the value of R should be _______Ω.

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

Q28.A series LCR circuit is designed to resonate at an angular frequency ω0 = 105 rad s−1. The circuit draws 16 W power from 120 V source at resonance. The value of resistance R in the circuit is ________ Ω.

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.

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)

Q29.In connection with the circuit drawn below, the value of current flowing through 2 kΩ resistor is______ × 10-4 A .

Q29.An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification 6, gives an unresolved image. A resolved image is observed at infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0. 6 m, if the focal length of the eyepiece is equal to ____ cm.

Q29.A ray of light passing through a prism (μ incidence is double the angle of refraction within the prism. Then, the angle of prism is (in degrees).

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 Kα X-ray of molybdenum has wavelength 0. 071 nm. If the energy of a molybdenum atom with a K electron knocked out is 27. 5 keV, the energy of this atom when an L electron is knocked out will be keV. (Round off to the nearest integer ) [h = 4. 14 × 10−15 eV s, c = 3 × 108 m s−1]