Practice Questions

Q23.A body of mass m = 10 kg is attached to one end of a wire of length 0.3 m. What is the maximum angular speed (in rad s−1 ) with which it can be rotated about its other end in a space station without breaking the wire? [Breaking stress of wire (σ)= 4.8 × 107 N m−2 and area of cross-section of the wire = 10−2 cm2 ]

Q23.If minimum possible work is done by a refrigerator in converting 100 grams of water at 0 °C to ice, how much heat (in calories) is released to the surroundings at temperature 27 °C (Latent heat of ice = 80 Cal / gram) to the nearest integer?

Q23.Initially a gas of diatomic molecules is contained in a cylinder of volume V1 at a pressure P1 and temperature 250 K. Assuming that 25% of the molecules get dissociated causing a change in number of moles. The pressure of the resulting gas at temperature 2000 K, when contained in a volume 2V1 is given by P2 . The ratio P2/P1 is -

Q23.A 5 μF capacitor is charged fully by a 220 V supply. It is then disconnected from the supply and is connected in series to another uncharged 2. 5 μF capacitor. If the energy change during the charge redistribution is 100X J then value of X to the nearest integer is :

Q23.Four resistance 40 Ω, 60 Ω, 90 Ω 110 Ω and make the arms of a quadrilateral ABCD. Across AC is a battery of emf 40 V and internal resistance negligible. The potential difference across BD in V is __________

Q23.A Carnot engine operates between two reservoirs of temperatures 900K and 300K . The engine performs 1200J of work per cycle. The heat energy (in J ) delivered by the engine to the low temperature reservoir, in a cycle, is _____________ JEE Main 2020 (07 Jan Shift 1) JEE Main Previous Year Paper

Q24.A compound microscope consists of an objective lens of focal length 1 cm and an eye piece of focal length 5 cm with a separation of 10 cm. The distance between an object and the objective lens, at which the strain on the eye is minimum is 40n cm. The value of n is.......

Q24.Four resistances of 15 Ω, 12 Ω, 4 Ω and 10 Ω respectively in cyclic order to form Wheatstone’s network. The resistance that is to be connected in parallel with the resistance of 10 Ω to balance the network is ______________ Ω.

Q24.Suppose that intensity of a laser is ( 315π ) W m−2. The rms electric field, in units of V m−1 associated with this source is close to the nearest integer is −(ε0 = 8. 86 × 10−12 C2 N m−2; c = 3 × 108 m s−1)

Q24.A Young's double-slit experiment is performed using monochromatic light of wavelength λ. The intensity of light at a point on the screen, where the path difference is λ, is K units. The intensity of light at a point where the path difference is λ is given by nK , where n is an integer. The value of n is 6 12

Q24.In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm . If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm ) is ______

Q24.A circular coil of radius 10 cm is placed in a uniform magnetic field of 3. 0 × 10−5 T with its plane perpendicular to the field initially. It is rotated at constant angular speed about an axis along the diameter of coil and perpendicular to magnetic field so that it undergoes half of rotation in 0. 2 s. The maximum value of EMF induced (in μV ) in the coil will be close to the integer....

Q24.The distance between an object and a screen is 100 cm. A lens can produce real image of the object on the screen for two different positions between the screen and the object. The distance between these two positions is 40 cm. If the power of the lens is close to ( 100N )D where N is an integer, the value of N is _________ JEE Main 2020 (04 Sep Shift 2) JEE Main Previous Year Paper

Q24.A 60pF capacitor is fully charged by a 20V supply. It is then disconnected from the supply and is connected to another uncharged 60pF capacitor in parallel. The electrostatic energy that is lost in this process by the time the charge is redistributed between them is (in nJ ) ________

Q24.An ideal cell of emf 10V is connected in circuit shown in figure. Each resistance is 2Ω . The potential difference (in V ) across the capacitor when it is fully charged is _____________

Q24.A bakelite beaker has volume capacity of 500 cc at 30°C. When it is partially filled with Vm volume (at 30°C ) of mercury, it is found that the unfilled volume of the beaker remains constant as temperature is varied. If γbester = 6 × 10−60°C−1, where γ is the coefficient of volume expansion, then Vm (in cc ) is close to …

Q25.In the circuit shown below, is working as a 8 V dc regulated voltage source. When 12 V is used as an input, the power dissipated (in mW ) in each diode is (Considering both zener diodes are identical)

Q25.The balancing length for a cell is 560cm in a potentiometer experiment. When an external resistance of 10Ω is connected in parallel to the cell, the balancing length changes by 60cm . If the internal resistance of the cell is n Ω , where n is an integer then value of n is ________ 10

Q25.Orange light of wavelength 6000 × 10–10 m illuminates a single slit of width 0. 6 × 10–4 m. The maximum possible number of diffraction minima produced on both sides of the central maximum is __________

Q25.The first member of the Balmer series of hydrogen atom has a wavelength of 6561 A . The wavelength of the second member of the Balmer series (in nm) is_____________

Q25.A beam of electrons of energy E scatters from a target having atomic spacing of 1 Å . The first maximum intensity occurs at θ = 60°. Then E(in eV) is........ (Planck's constant h = 6. 64 × 10−34 Js, 1 eV = 1. 6 × 10−19J, electron mass m = 9. 1 × 10−31 kg)

Q25.The output characteristics of a transistor is shown in the figure. When VCE is 10V and IC = 4 .0 mA , then value of βac is JEE Main 2020 (06 Sep Shift 2) JEE Main Previous Year Paper

Q25.A light ray enters a solid glass sphere of refractive index μ = √3 at an angle of incidence 60°. The ray is both reflected and refracted at the farther surface of the sphere. The angle (in degrees) between the reflected and refracted rays at this surface is _____________.

Q25.The surface of a metal is illuminated alternately with photons of energies E1 = 4 eV and E2 = 2. 5 eV respectively. The ratio of maximum speeds of the photoelectrons emitted in the two cases is 2. The work function of the metal in (eV) is..........

Q25.When radiation of wavelength A is used to illuminate a metallic surface, the stopping potential is V . When the same surface is illuminated with radiation of wavelength 3A , the stopping potential is V4 . If the threshold wavelength for the metallic surface is nλ then value of n will be :