Practice Questions

Q23.When a long glass capillary tube of radius 0. 015 cm is dipped in a liquid, the liquid rises to a height of 15 cm within it. If the contact angle between the liquid and glass to close to 0°, the surface tension of the liquid, in milliNewton m−1, is [ρ(liqued) = 900 kg m−3, g = 10 m s−2] (Given answer in closed integer)

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.In a meter bridge experiment S is a standard resistance. R is a resistance wire. It is found that balancing length is l = 25cm. If R is replaced by a wire of hall length and half diameter that of R of same material, then the JEE Main 2020 (09 Jan Shift 2) JEE Main Previous Year Paper balancing distance l' (in cm ) will now be ______________.

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

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.In a series LR circuit, power of 400 W is dissipated from a source of 250 V, 50 Hz. The power factor of the circuit is 0. 8 . In order to bring the power factor to unity, a capacitor of value C is added in series to the L and R. Taking the value of C as ( 3πn ) μF , then value of n is

Q23.A wire of density 9 × 10–3 kg cm–3 is stretched between two clamps 1 m apart. The resulting strain in the wire is 4. 9 × 10–4 . The lowest frequency of the transverse vibrations in the wire (Young's modulus of wire Y = 9 × 1010 Nm–2 ), (to the nearest integer),_______

Q23.A one metre long (both ends open) organ pipe is kept in a gas that has double the density of air at STP. Assuming the speed of sound in air at STP is 300 m/s, the frequency difference between the fundamental and second harmonic of this pipe is __________ Hz. JEE Main 2020 (08 Jan Shift 1) JEE Main Previous Year Paper

Q23. M grams of steam at 100oC is mixed with 200g of ice at its melting point in a thermally insulated container. If it produces liquid water at 40oC [heat of vaporization of water is 540cal/g and heat of fusion of ice is 80cal/g ], the value of M is ________

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 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 …

Q24.In a Young's double slit experiment 15 fringes are observed on a small portion of the screen when light of wavelength 500 nm is used. Ten fringes are observed on the same section of the screen when another light source of wavelength λ is used. Then the value of λ is (in nm ) __________.

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.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.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.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.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.The series combination of two batteries, both of the same emf 10V, but different internal resistance of 20 Ω and 5 Ω, is connected to the parallel combination of two resistors 30 Ω and x Ω. The voltage difference across the battery of internal resistance 20 Ω is zero, the value of x (in Ω) is____ ∘

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.In a fluorescent lamp choke (a small transformer) 100V of reverse voltage is produced when the choke current changes uniformly from 0.25A to 0 in a duration of 0.025ms . The self-inductance of the choke (in mH ) is estimated to be ________

Q24.A loop ABCDEFA of straight edges has six corner points A(0, 0, 0), B(5, 0, 0), C(5, 5, 0), D(0, 5, 0), E(0, 5, 5) and F(0, 0, 5) . The magnetic field in this region is → B = + ABCDEFA (in Wb ) is _____________ (3ˆi 4ˆk)T . The quantity of flux through the loop

Q24.A galvanometer coil has 500 turns and each turn has an average area of 3 × 10−4m2 . If a torque of 1. 5 Nm is required to keep this coil parallel to a magnetic field when a current of 0. 5A is flowing through it, the strength of the field (in T) is _________ .

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 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.A prism of angle A = 1° μ = 1. 5 . A good estimate for the minimum angle of deviation (in degrees) is close to N . Value of N is … … … 10