Practice Questions

Q25.The area of cross-section of a railway track is 0. 01 m2. The temperature variation is 10 °C. Coefficient of linear expansion of material of track is 10−5 ∘C−1. The energy stored per meter in the track is J m−1. (Young's modulus of material of track is 1011 N m−2 )

Q25.In the figure given, the electric current flowing through the 5 kΩ resistor is x mA . The value of x to the nearest integer is ________.

Q25.Two cars X and Y are approaching each other with velocities 36 km h−1 and 72 km h−1 respectively. The frequency of a whistle sound as emitted by a passenger in car X, heard by the passenger in car Y is 1320 Hz. If the velocity of sound in air is 340 ms−1, the actual frequency of the whistle sound produced is ________ Hz.

Q25.A long solenoid with 1000 turns m-1 has a core material with relative permeability 500 and volume 103 cm3 . If the core material is replaced by another material having relative permeability of 750 with same volume maintaining same current of 0 . 75 A in the solenoid, the fractional change in the magnetic moment of 𝑥 the core would be approximately . Find the value of 𝑥. 499

Q25.Time period of a simple pendulum is T . The time taken to complete 5 oscillations starting from mean position 8 is α T . The value of α is ______ . 12 JEE Main 2021 (26 Feb Shift 2) JEE Main Previous Year Paper Q26. 27 similar drops of mercury are maintained at 10 V each. All these spherical drops combine into a single big drop. The potential energy of the bigger drop is ___________ times that of a smaller drop.

Q25.Two circuits are shown in figure (a) and (b). At a frequency of _______ rad s−1 the average power dissipated in one cycle will be the same in both the circuits.

Q25.The mass per unit length of a uniform wire is 0. 135 g cm−1 . A transverse wave of the form y = −0. 21 sin(x + 30t) is produced in it, where x is in meter and t is in second. Then, the expected value of tension in the wire is x × 10−2 N . Value of x is (Round-off to the nearest integer)

Q25.A particle executes simple harmonic motion represented by displacement function as x(t) = A sin(ωt + ϕ). If the position and velocity of the particle at t = 0 s are 2 cm and 2ω cm s−1 respectively, then its amplitude is x√2 cm where the value of x is

Q25.Consider two identical springs each of spring constant k and negligible mass compared to the mass M as shown. Fig. 1 shows one of them and Fig. 2 shows their series combination. The ratios of time period of oscillation of the two SHM is Tb = √x, where value of x is ______. Ta (Round off to the Nearest Integer)

Q25.If the maximum value of accelerating potential provided by a radio frequency oscillator is 12 kV . The number of revolution made by a proton in a cyclotron to achieve one sixth of the speed of light is: [mp = 1. 67 × 10−27 kg, e = 1. 6 × 10−19 C, Speed of light = 3 × 108 m s−1]

Q25.The width of one of the two slits in a Young's double slit experiment is three times the other slit. If the amplitude of the light coming from a slit is proportional to the slit-width, the ratio of minimum to maximum intensity in the interference pattern is 𝑥: 4 where 𝑥 is _______ .

Q25.Two cars are approaching each other at an equal speed of 7. 2 km hr−1. When they see each other, both blow horns having a frequency of 676 Hz. The beat frequency heard by each driver will be _______ Hz. [Velocity of sound in air is 340 m s−1.

Q25.The electric field in a region is given by E = ( 5 E0ˆi + 5 E0ˆj) through the rectangular surface of area 0. 2 m2 (parallel to y −z plane) to that of the surface of area 0. 3 m2 (parallel to x −z plane) is a : b = a : 2, where a =? [Here ˆi, ˆj and ˆk are unit vectors along x, y and z -axes respectively] Q26. 512 identical drops of mercury are charged to a potential of 2 V each. The drops are joined to form a single drop. The potential of this drop is V in Volt.

Q26.A particle of mass 9. 1 × 10−31 kg travels in a medium with a speed of 106 m s−1 and a photon of radiation of linear momentum 10−27 kg m s−1 travels in a vacuum. The wavelength of the photon is ____ times the wavelength of the particle. ∘

Q26.A sinusoidal voltage of peak value 250 V is applied to a series LCR circuit, in which R = 8 Ω, L = 24 mH and C = 60 μF. The value of power dissipated at resonant condition is x kW . The value of x to the nearest integer is _______.

Q26.A resonance circuit having inductance and resistance 2 × 10-4 H and 6 . 28 Ω respectively oscillates at 10 MHz frequency. The value of quality factor of this resonator is_______. 𝜋= 3 . 14

Q26.A capacitor of 50μF is connected in a circuit as shown in figure. The charge on the upper plate of the capacitor is _________ μC.

Q26.The electric field in a region is given by E = 5 E0ˆi + 5 E0ˆj field through a rectangular surface, area 0. 4 m2 parallel to the Y −Z plane is _______ N m2 C−1 .

Q26.The peak electric field produced by the radiation coming from the 8 W bulb at a distance of 10 m is x V m−1 . The efficiency of the bulb is 10% and it is a point source. The value of x is, 10 √μ0cπ

Q26.A point charge of +12 μC is at a distance 6 cm vertically above the centre of a square of side 12 cm as shown in figure. The magnitude of the electric flux through the square will be _______ ×103 N m2 C−1. JEE Main 2021 (24 Feb Shift 2) JEE Main Previous Year Paper

Q26.The amplitude of wave disturbance propagating in the positive x-direction is given by y = 1 at time t = 0 (1+x)2 and y = 1 at t = 1 s, where x and y are in metres. The shape of wave does not change during the 1+(x−2)2 propagation. The velocity of the wave will be m s−1.

Q26.The ratio of the equivalent resistance of the network (shown in figure) between the points a and b when switch is open and switch is closed is x : 8 . The value of x is JEE Main 2021 (27 Aug Shift 2) JEE Main Previous Year Paper

Q26.An electric bulb rated as 200 W at 100 V is used in a circuit having 200 V supply. The resistance 𝑅 that must be put in series with the bulb so that the bulb delivers the same power is ______ Ω.

Q26.A source and a detector move away from each other in absence of wind with a speed of 20 m s−1 , with respect to the ground. If the detector detects a frequency of 1800 Hz of the sound coming from the source, then the original frequency of source considering the speed of sound in the air 340 m s−1 will be _____ Hz .

Q26.At very high frequencies, the effective impedance of the given circuit will be _________Ω .