Practice Questions

Q42.The center of mass of a thin rectangular plate (fig - x ) with sides of length a and b, whose mass per unit area (σ) varies as σ = σ0xab (where σ0 is a constant), would be (1) ( 23 a, 2b ) (2) ( a2 , 2b ) (3) ( 13 a, 2b ) (4) ( 23 a, 23 b)

Q42. A poly-atomic molecule ( CV = 3R, CP = 4R, where R is gas constant) goes from phase space point A (PA = 105 Pa, VA = 4 × 10−6 m3) to point B (PB = 5 × 104 Pa, VB = 6 × 10−6 m3) to point 2025 (29 Jan Shift 2) JEE Main Previous Year Paper C (PC = 104 Pa, VC = 8 × 10−6 m3). A to B is an adiabatic path and B to C is an isothermal path. The net heat absorbed per unit mole by the system is : (1) 500R(ln 3 + ln 4) (2) 450R(ln 4 −ln 3) (3) 500R ln 2 (4) 400R ln 4

Q42.In the diagram given below, there are three lenses formed. Considering negligible thickness of each of them as compared to |R1| and |R2|, i.e., the radii of curvature for upper and lower surfaces of the glass lens, the power of the combination is (1) 1 − + |R2| |R2| 6 ( |R1|1 1 ) (2) −16 ( |R1|1 1 ) (3) 1 + − |R2| |R2| 6 ( |R1|1 1 ) (4) −16 ( |R1|1 1 )

Q42.A parallel plate capacitor was made with two rectangular plates, each with a length of l = 3 cm and breath of b = 1 cm . The distance between the plates is 3μ m . Out of the following, which are the ways to increase the capacitance by a factor of 10 ? A. l = 30 cm, b = 1 cm, d = 1μ m B. l = 3 cm, b = 1 cm, d = 30μ m C. l = 6 cm, b = 5 cm, d = 3μ m D. l = 1 cm, b = 1 cm, d = 10μ m E. l = 5 cm, b = 2 cm, d = 1μ m Choose the correct answer from the options given below: 2025 (24 Jan Shift 1) JEE Main Previous Year Paper (1) A only (2) C only (3) B and D only (4) C and E only

Q43.The maximum percentage error in the measurment of density of a wire is [Given, mass of wire = (0.60 ± 0.003)g radius of wire = (0.50 ± 0.01)cm length of wire = (10.00 ± 0.05)cm] (1) 8 (2) 5 (3) 4 (4) 7 for another diatomic molecules, but for rigid molecules and γ2 =

Q43.The energy of a system is given as E(t) = α3e−βt , where t is the time and β = 0.3 s−1 . The errors in the measurement of α and t are 1.2% and 1.6% , respectively. At t = 5 s, maximum percentage error in the energy is : (1) 6% (2) 8.4% (3) 11.6% (4) 4%

Q43.A parallel plate capacitor of capacitance 1μ F is charged to a potential difference of 20 V . The distance between plates is 1μ m . The energy density between plates of capacitor is. (1) 2 × 10−4 J/m3 (2) 1.8 × 105 J/m3 (3) 1.8 × 103 J/m3 (4) 2 × 102 J/m3

Q43.Consider I1 and I2 are the currents flowing simultaneously in two nearby coils 1 & 2, respectively. If L1 = self inductance of coil 1, M12 = mutual inductance of coil 1 with respect to coil 2, then the value of induced emf in coil 1 will be Options (1) ε1 = −L1 dI2dt −M12 dI1dt (2) ε1 = −L1 dI1dt −M12 dI2dt (3) ε1 = −L1 dI1dt −M12 dI1dt (4) ε1 = −L1 dI1dt + M12 dI2dt

Q43.Which of the following circuits has the same outpur as that of the given circuit? (1) (2) (3) (4)

Q43.Consider a parallel plate capacitor of area A (of each plate) and separation 'd' between the plates. If E is the electric field and ε0 is the permittivity of free space between the plates, then potential energy stored in the capacitor is (1) ε0E2Ad (2) 12 ε0E2Ad (3) 1 4 ε0E2Ad (4) 34 ε0E2Ad

Q43.Match List - I with List - II. List - I List - II (A) Magnetic induction (I) Ampere meter 2 (B) Magnetic intensity (II) Weber (C) Magnetic flux (III) Gauss (D) Magnetic moment (IV) Ampere/meter (1) (A)-(I), (B)-(II), (C)-(III), (D)-(IV) (2) (A)-(III), (B)-(IV), (C)-(I), (D)-(II) (3) (A)-(III), (B)-(II), (C)-(I), (D)-(IV) (4) (A)-(III), (B)-(IV), (C)-(II), (D)-(I)

Q44.An object of mass ' m ' is projected from origin in a vertical xy plane at an angle 45∘ with the x axis with an initial velocity v0 . The magnitude and direction of the angular momentum of the object with respect to origin, when it reaches at the maximum height, will be [ g is acceleration due to gravity] (1) mv3 o along negative z -axis (2) mv3 o along positive z -axis 2√2g 4√2g (3) mv3o along negative z -axis (4) mv3o along positive z -axis 4√2g 2√2g

Q44.A parallel-plate capacitor of capacitance 40μ F is connected to a 100 V power supply. Now the intermediate space between the plates is filled with a dielectric material of dielectric constant K = 2. Due to the introduction of dielectric material, the extra charge and the change in the electrostatic energy in the capacitor, respectively, are (1) 4 mC and 0.2 J (2) 8 mC and 2.0 J (3) 2 mC and 0.4 J (4) 2 mC and 0.2 J 2025 (22 Jan Shift 1) JEE Main Previous Year Paper

Q44.A point charge causes an electric flux of −2 × 104Nm2C−1 to pass through a spherical Gaussian surface of 8.0 cm radius, centred on the charge. The value of the point charge is : (Given ϵ0 = 8.85 × 10−12C2 N−1 m−2 ) (1) 15.7 × 10−8C (2) 17.7 × 10−8C (3) −15.7 × 10−8C (4) −17.7 × 10−8C

Q44.Match List - I with List - II. List - I List - II (A) Permeability of free space (I) [M L2 T−2] (B) Magnetic field (II) [M T−2 A−1] (C) Magnetic moment (III) [M L T−2 A−2] (D) Torsional constant (IV) [L2 A] Choose the correct answer from the options given below : (1) (A)-(IV), (B)-(III), (C)-(I), (D)-(II) (2) (A)-(III), (B)-(II), (C)-(IV), (D)-(I) (3) (A)-(I), (B)-(IV), (C)-(II), (D)-(III) (4) (A)-(II), (B)-(I), (C)-(III), (D)-(IV)

Q44.For a diatomic gas, if γ1 = ( CpCv ) ( CpCv ) also having vibrational modes. Then, which one of the following options is correct ? (Cp and Cv are specific heats of the gas at constant pressure and volume) 2025 (22 Jan Shift 2) JEE Main Previous Year Paper (1) γ2 = γ1 (2) 2γ2 = γ1 (3) γ2 < γ1 (4) γ2 > γ1 →

Q45.For an experimental expression y = 32.3×112527.4 , where all the digits are significant. Then to report the value of y we should write (1) y = 1326.19 (2) y = 1330 (3) y = 1326.186 (4) y = 1326.2

Q45.A proton of mass ' mp ' has same energy as that of a photon of wavelength ' λ '. If the proton is moving at non- relativistic speed, then ratio of its de Broglie wavelength to the wavelength of photon is. (1) 1 (2) 1 c √Emp c √2Emp (3) 1 (4) 1 E 2c √Emp c √ 2 mp

Q45. In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage VAB is correctly represented by : (1) VAB would be zero at all times (2) (3) (4)

Q45.An electric dipole is placed at a distance of 2 cm from an infinite plane sheet having positive charge density σo . Choose the correct option from the following. (1) Potential energy and torque both are maximum. (2) Torque on dipole is zero and net force is directed away from the sheet. (3) Torque on dipole is zero and net force acts (4) Potential energy of dipole is minimum and torque towards the sheet. is zero.

Q45.A force F = 2^i + b^j + ^k is applied on a particle and it undergoes a displacement ^i −2^j −^k. What will be the value of b, if work done on the particle is zero. (1) 0 (2) 1 2 (3) 2 (4) 1 3

Q45.Which of the following resistivity ( ρ ) v/s temperature (T) curves is most suitable to be used in wire bound standard resistors? (1) (2) (3) (4)

Q45.In photoelectric effect an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V , what is the wavelength of the em- wave ? (Given hc = 1242eVnm where h is the Planck's constant and c is the speed of light in vaccum.) 2025 (23 Jan Shift 2) JEE Main Previous Year Paper (1) 300 nm (2) 400 nm (3) 600 nm (4) 200 nm

Q45.A body of mass ' m ' connected to a massless and unstretchable string goes in verticle circle of radius ' R 'under gravity g. The other end of the string is fixed at the center of circle. If velocity at top of circular path is n√gR, where, n ⩾1, then ratio of kinetic energy of the body at bottom to that at top of the circle is (1) n2 (2) n2+4 n2+4 n2 (3) n+4 (4) n n n+4

Q62.If a0 is denoted as the Bohr radius of hydrogen atom, then what is the de-Broglie wavelength (λ) of the electron present in the second orbit of hydrogen atom? [n : any integer] (1) 8πa0 (2) 2a0 n nπ (3) 4n (4) 4πa0 πa0 n